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Before yesterdaySpace – EarthSky

See a nova or “new” star. V1405 Cas is now visible to the eye

May 13th 2021 at 11:04
A starfield with an open star cluster and a nebula, with one star (the nova) marked.

View at EarthSky Community Photos. | Eliot Herman caught Nova V1405 Cas [between tickmarks] on May 11, 2021, from Mayhill, New Mexico. He wrote: “Nova V1405 Cassiopeiae has brightened to magnitude 5.4. The nova was magnitude +7.8 since shortly after its discovery in March 2021, but it suddenly brightened. Magnitude 5 novas are uncommon. The nova is visible for about an hour before dawn. The open cluster M52 and the Bubble Nebula are also shown in the photo.” Thank you, Eliot!

First spotted in March, Nova V1405 Cas has suddenly flared in brightness over the past week, enabling observers to spot it without binoculars or a telescope. You can see it too, if you observe from a dark-sky site and know just where to look! Plus … what is it? It’s not a supernova or exploding star. What causes a star to appear where no star was before? You’ll find charts, photos from our community, and an explanation here.

Japanese photographer Yuji Nakamura spotted a nova located in the direction of the constellation Cassiopeia the Queen on March 18, 2021. At that time, this light in our sky – which has been named V1405 Cas – was shining at about magnitude 9.6, much too faint to see with the eye. Just a few days later, though, the nova had brightened to about magnitude 7.6, making it bright enough to be visible with binoculars. Now that the nova is around magnitude 5.5, those with keen eyesight and dark skies can hunt it down without any optical aid at all, though it may help to first locate it with binoculars or a telescope and then your eyes alone. The charts below will help you star hop to the nova.

Cassiopeia is very low on the northern horizon. Your viewing location will have to be free of trees, buildings and hills and free of light pollution, or you can wait until the middle of the night when Cassiopeia rises a bit higher. The nova is between the W shape of Cassiopeia and the house shape that makes up Cepheus. Take the two stars on the right side of Cassiopeia’s W shape and use them to draw a line toward Cepheus. Extend the line for approximately the same distance as the two stars are apart from each other and start looking for a little star cluster known as M52. Then look just off of M52 and use the map to pinpoint the nova. The charts and photos shown here will guide you. The first star chart is for March, but the location of the nova between Cassiopeia and Cepheus has not changed, even though the constellations’ locations have shifted a bit on the sky’s dome.

What is a nova? This particular object is likely what’s called a classical nova, seen only once (so far), caused by two stars’ interactions in a binary star system. The system causing a nova consists of a white dwarf and likely a star similar to our sun, in an extremely close orbit, perhaps lasting only hours (contrast that orbit to Earth’s orbit around the sun of 365 days). Being so close, the more massive white dwarf siphons gas – mostly hydrogen – from its companion star. An accretion disk forms around the white dwarf, which, in turn, deposits a hydrogen layer onto the surface of the white dwarf. This causes temperatures and pressures to build, finally creating a runaway thermonuclear reaction. As the COSMOS The SAO Encyclopedia of Astronomy explains:

The energy released through this process ejects the majority of the unburnt hydrogen from the surface of the star in a shell of material moving at speeds of up to 1,500 km/s. This produces a bright but short-lived burst of light – the nova.

Novae happen much more often than supernovae, but only a few of them reach magnitudes visible to the unaided eye. One of the last novae that could be spotted without optical aid was in 2013 in the constellation Delphinus, so take advantage of this nova while it lasts!

V1405 Cas is located at right ascension 23h 24m 48s, declination +61° 11′ 15″.

Star chart with constellation lines showing the nova as a red dot.

Follow the bottom 2 stars in the M- or W-shaped constellation Cassiopeia to find the new nova. Image via Bob King/ Sky & Telescope.

Star chart with closeup on nova region.

You can star hop from moderately bright stars to the nova as shown here. Image via Bob King/ Sky & Telescope.

Star field with oblects labeled including bright nova.

View at EarthSky Community Photos. | David Hoskin in Halifax, Nova Scotia, Canada, captured this photo of the nova on May 11, 2021. He wrote: “Nova Cas 21 has brightened dramatically and can now be seen with the unaided eye from a dark-sky site. I captured this image of Nova Cas 21 and its surroundings early this morning. Nova Cas 21 is currently at least as bright as HIP 115395, which is a +5.55-magnitude star.” Thanks, David!

Dark sky with trees below and star pinpointed with markers.

View larger. | This wider shot shows how nova V1405 Cas can be spotted without optical aid using just your eyes. (Nova indicated with red hashmarks just left of top of tallest tree.) Image via Project Nightflight. Thank you, Project Nightflight!

Labeled starfield with box around the nova.

View at EarthSky Community Photos. | Tara Mostofi in California and Alexandru Barbovschi in Moldova collaborated on this image of nova V1405 Cas on March 21, 2021. You’ll see it inside the green square (and inset) on this image. Thank you, Alexandru and Tara!

Bottom line: The nova in Cassiopeia named V1405 has flared to magnitude 5.4, allowing observers to spot it without the help of telescopes or binoculars.

Voyager 1 detects a hum in interstellar space

May 12th 2021 at 15:36
Diagram of the Voyager spacecraft leaving the heliosphere.

Voyager 1 is said to have sailed out of our solar system in 2012, when it crossed the heliopause into interstellar space. Image via NASA.

Voyager 1 left Earth in 1977 and crossed the boundary of our sun’s magnetic influence (the heliopause) in 2012. It’s now traveling in the vastness of interstellar space – the space between the stars – and is, at present, the most distant human-made object from us. Interstellar space isn’t quite as empty as a vacuum, and a team of scientists announced on May 10, 2021, that Voyager 1 has now sent back a message, saying it’s detected a faint, monotonous hum of interstellar gas (plasma). Astronomer Stella Koch Ocker of Cornell University led the study and, in a statement, described Voyager 1’s discovery:

It’s very faint and monotone, because it is in a narrow-frequency bandwidth. We’re detecting the faint, persistent hum of interstellar gas.

The study was published May 10, 2021, in the peer-reviewed journal Nature Astronomy.

Young woman with glasses and medium-length brown hair in front of galaxy photo.

Astronomer Stella Koch Ocker led the study leading to the discovery of a low-level hum in interstellar space. Image via Cornell University.

Although Voyager 1 is traveling in interstellar space, it still feels some influence from the solar wind, a stream of charged particles from our sun. This stream from our sun is no longer the dominant force affecting Voyager 1, however; similar “winds” from other stars mix in. As Voyager 1 reads its environment, it allows scientists to understand how the interstellar medium and solar wind interact and how the the bubble of the solar system’s heliosphere is shaped by external forces.

Voyager 1 has an instrument called a Plasma Wave System, which has been detecting larger eruptions from the sun that affect the plasma, or ionized gas, in interstellar space. It’s when the eruptions are quiet that there’s a background hum. Team member James Cordes of Cornell University described the hum not as an annoying drone, but as something much more pleasant:

The interstellar medium is like a quiet or gentle rain. In the case of a solar outburst, it’s like detecting a lightning burst in a thunderstorm and then it’s back to a gentle rain.

The low-level hum let scientists track how interstellar plasma is distributed in the space through which Voyager 1 is passing. That’s huge! We’ve never had a spacecraft so far from Earth before and so never before could obtain this sort of direct measurement. Team member Shami Chatterjee of Cornell University explained how the hum helps scientists learn more about the interstellar plasma:

We’ve never had a chance to evaluate it. Now we know we don’t need a fortuitous event related to the sun to measure interstellar plasma. Regardless of what the sun is doing, Voyager is sending back detail. The craft is saying, ‘Here’s the density I’m swimming through right now. And here it is now. And here it is now. And here it is now.’ Voyager is quite distant and will be doing this continuously.

Voyager 1 is 14 billion miles (22.5 billion km) from Earth. The signals it sends back to us require nearly an entire earthly day to travel back to Earth. In other words, Voyager 1 is nearly 1 light-day away. For this spacecraft launched in 1977 to still be working outside our solar system and transmitting data is a truly stupendous achievement. Ocker said:

Scientifically, this research is quite a feat. It’s a testament to the amazing Voyager spacecraft. It’s the engineering gift to science that keeps on giving.

Small, boxy spacecraft with a big dish antenna on part deep orange, part black background.

This artist’s concept shows Voyager 1 leaving the solar system and the greater influence of solar particles and entering interstellar space. Image via NASA/ JPL-Caltech.

Bottom line: Voyager 1 has detected a faint, monotonous hum from plasma (ionized gas) in interstellar space.

Source: Persistent plasma waves in interstellar space detected by Voyager 1

Via Cornell University

Astronomers photograph giant exoplanet in unusual large orbit

May 11th 2021 at 07:34
Bright spots in ring shape and another bright dot on black background, with text annotations.

Direct image of the giant exoplanet YSES 2b (marked as “b”). The star in the middle of the bright dots has been hidden to block its light. Image via ESO/ SPHERE/ VLT/ Bohn et al./ Astronomie.nl.

Astronomers have discovered many giant planets, similar to Jupiter or Saturn, orbiting other stars. Some of these – called hot Jupiters – are unlike any planets in our solar system, however, circling much closer to their stars than any of our sun’s planets orbit the sun. Hot Jupiters appear to be quite common, even though none exist in our own solar system. This spring (April, 2021), astronomers at Leiden University announced an opposite planet of sorts, a giant world called YSES 2b, orbiting much farther out from its star than has typically been seen before. The researchers captured a direct image of this planet, something not easy to do. The planet orbits its star a whopping 20 times farther than Jupiter orbits our sun. That’s the equivalent of 110 times the distance from Earth to the sun.

The details of the discovery were published in the peer-reviewed journal Astronomy & Astrophysics on April 19, 2021.

YSES 2b is located 360 light-years away, in the direction to the southern constellation Musca the Fly. It is a young gas giant six times more massive than Jupiter. Other similar gas giants have been found before, but this one is a bit different.

Large glowing Jupiter-like planet with sun in distance.

Artist’s concept of a young gas giant exoplanet, similar to YSES 2b. Image via Danielle Futselaar/ Franck Marchis/ SETI Institute/ The Conversation.

The researchers don’t yet know why the planet is so far from its star. Scientists normally have two models – core accretion and disk instability – to explain the formation of such large planets, but this giant world doesn’t seem to fit either of them.

The first, core accretion, says that the planet formed where it is, due to planetesimals collecting together to form a rocky core, heavy enough to collect gas around it. But if that were the case, it is far too heavy. This is because there is generally too little material that far out from a star to make a planet that big.

The other theory, disk instability, is that the planet formed by a gravitational instability in the original circumstellar disk of material that surrounds a young star (and this star is only 14 million years old, still a baby star if you will). But, the planet we see now isn’t heavy enough for that process to have created it.

What other possibilities are there? The scientists think that it is possible the planet first formed by core accretion closer to the star, but then migrated outwards to a much more distant orbit. For that to work, however, the gravitational influence of a second planet would be needed, and such a planet hasn’t been found yet.

Smiling young man with eyeglasses in suit jacket and dress shirt.

The discovery team was led by Alexander Bohn at Leiden University. Image via Leiden University.

YSES 2b was discovered as part of the Young Suns Exoplanet Survey (YSES). Researchers will continue to study this peculiar world as well as search for more planets orbiting young sun-like stars. Lead author Alexander Bohn at Leiden University stated that:

By investigating more Jupiter-like exoplanets in the near future, we will learn more about the formation processes of gas giants around sun-like stars.

At the moment, only large planets like YSES 2b can be directly imaged, and even then still just look like a bright dot. Distant Earth-sized worlds are too small for telescopes to observe, but that will change in the years ahead as the technology advances.

In 2020, the telescope used for YSES, the Very Large Telescope (VLT) in Chile, also imaged a multi-planet system around the sun-like star TYC 8998-760-1, which is 300 light-years away. This was the first multi-planet system ever imaged directly, with the first detections made in 2018 and 2020. A special planet finder instrument, called SPHERE, on the telescope was used to obtain the images. This instrument can capture both direct and indirect light coming from exoplanets. Bohn said at the time:

This discovery is a snapshot of an environment that is very similar to our solar system, but at a much earlier stage of its evolution.

Two colored disks around bright spots on black background, with text annotations.

There are two formation scenarios for planets, the Core Accretion Model and the Disk Instability Model. At present, the formation of YSES 2b is difficult to explain by either model. Image via NASA/ ESA/ A. Feild/ Sky & Telescope.

Co-author Matthew Kenworthy added:

Even though astronomers have indirectly detected thousands of planets in our galaxy, only a tiny fraction of these exoplanets have been directly imaged. Direct observations are important in the search for environments that can support life.

The discovery of YSES 2b provides a challenge to astronomers in terms of how it formed, and will help scientists better understand planetary formation processes.

Bottom line: Astronomers have directly imaged a giant gas exoplanet that has an unusually large orbit.

Source: Discovery of a directly imaged planet to the young solar analog YSES 2

Via Astronomie.nl

Swimming up sky and up river

May 10th 2021 at 11:43
Night sky chart with constellations and objects labeled.

View larger. | Chart showing Mercury on Tuesday, May 11, 2021, 45 minutes after sunset as seen from 40 degrees N. latitude. The arrows through Mercury, the sun, Venus, and Mars show their movements, against the starry background, over a span of 5 days. You can see that Mercury is eastering faster than the sun; it will slow toward May 17, the date of its greatest distance from the sun in our sky. Image via Guy Ottewell.

Guy Ottewell originally published these charts on May 10, 2021, at his blog. Reprinted here with permission.

Little Mercury, elusive in the sun’s glare, is becoming more and more findable in the dusk, as it climbs toward its easternmost elongation – its greatest angular distance from the sun in our sky – on May 17, 2021. That will be its highest evening appearance of the year, for our Northern Hemisphere.

This year, Mercury swings three and a half times into the evening sky and three times into the morning sky. The graph below summarizes Mercury’s three morning and three-and-a-half evening appearances of the year.

Graphs of Mercury's appearances in the sky in 2021.

View larger. | This graph compares Mercury’s 3 morning and 3 1/2 evening appearances of 2021, using gray for the evening and blue for the morning excursions. The top figures are the maximum elongations, reached at the top dates shown beneath. Curves show the altitude of the planet above the horizon at sunrise or sunset, for latitude 40° north (thick line) and 35° south (thin), with maxima reached at the parenthesized dates below (40° north bold). Image via Guy Ottewell.

Meanwhile, in the Blue Planet Department

On the evening of May 9, another small wanderer – as the originally Greek word planet means – a young minke whale, about four yards long, reached an extreme elongation from the sea. That is, se (my pronoun, which I’d rather use than “he or she” or “it”) swam up the river Thames to the farthest point possible: the Richmond lock, which partially stops the tidal river.

At the side of the lock is a line of rollers on which boats can be pulled past. The tide must have been slightly over them, and the whale tried to get through, and became stuck.

This was about 7 a.m. A team from the London fire brigade and the Royal National Lifeboat Institute managed to get hem off the rollers by 1 a.m. Se was towed downriver, but at Isleworth – where we live – se broke free, swam away, and disappeared. Latest we know is that the public is asked to report any sighting of the whale, which is not in good health.

Read more about the whale at Guy Ottewell’s blog, or read about the whale’s fate here.

A young whale stuck in a narrow concrete channel.

Photo via Guy Ottewell.

Bottom line: Two beautiful charts by Guy Ottewell, one showing Mercury’s movement in the western sky at dusk around May 11, 2021, and the other comparing Mercury’s six appearances in our sky this year.

Via Guy Ottewell

Warp drives: Physicists give chances of faster-than-light space travel a boost

May 10th 2021 at 11:43
Rocket  hurtling toward a black circle with many-colored rays coming out of it.

View larger. | Artist’s concept of faster-than-light travel through a wormhole. If it were possible, it would enable humans to reach other stars in a reasonable amount of time. Image via Les Bossinas/ NASA/ Wikimedia Commons.

By Mario Borunda, Oklahoma State University

The closest star to Earth is Proxima Centauri. It is about 4.25 light-years away, or about 25 trillion miles (40 trillion km). The fastest ever spacecraft, the now-in-space Parker Solar Probe will reach a top speed of 450,000 miles (724,000 km) per hour. It would take just 20 seconds to go from Los Angeles to New York City at that speed, but it would take the solar probe about 6,633 years to reach Earth’s nearest neighboring solar system.

If humanity ever wants to travel easily between stars, people will need to go faster than light. But so far, faster-than-light travel is possible only in science fiction.

In Isaac Asimov’s Foundation series, humanity can travel from planet to planet, star to star or across the universe using jump drives. As a kid, I read as many of those stories as I could get my hands on. I am now a theoretical physicist and study nanotechnology, but I am still fascinated by the ways humanity could one day travel in space.

Some characters – like the astronauts in the movies “Interstellar” and “Thor” – use wormholes to travel between solar systems in seconds. Another approach – familiar to “Star Trek” fans – is warp drive technology. Warp drives are theoretically possible if still far-fetched technology. Two recent papers made headlines in March when researchers claimed to have overcome one of the many challenges that stand between the theory of warp drives and reality.

But how do these theoretical warp drives really work? And will humans be making the jump to warp speed anytime soon?

A circle on a flat blue plane with the surface dipping down in front and rising up behind.

This 2-dimensional representation shows the flat, unwarped bubble of spacetime in the center where a warp drive would sit surrounded by compressed spacetime to the right (downward curve) and expanded spacetime to the left (upward curve). Image via AllenMcC/ Wikimedia Commons.

Compression and expansion

Physicists’ current understanding of spacetime comes from Albert Einstein’s theory of General Relativity. General Relativity states that space and time are fused and that nothing can travel faster than the speed of light. General relativity also describes how mass and energy warp spacetime – hefty objects like stars and black holes curve spacetime around them. This curvature is what you feel as gravity and why many spacefaring heroes worry about “getting stuck in” or “falling into” a gravity well. Early science fiction writers John Campbell and Asimov saw this warping as a way to skirt the speed limit.

What if a starship could compress space in front of it while expanding spacetime behind it? “Star Trek” took this idea and named it the warp drive.

In 1994, Miguel Alcubierre, a Mexican theoretical physicist, showed that compressing spacetime in front of the spaceship while expanding it behind was mathematically possible within the laws of General Relativity. So, what does that mean? Imagine the distance between two points is 10 meters (33 feet). If you are standing at point A and can travel one meter per second, it would take 10 seconds to get to point B. However, let’s say you could somehow compress the space between you and point B so that the interval is now just one meter. Then, moving through spacetime at your maximum speed of one meter per second, you would be able to reach point B in about one second. In theory, this approach does not contradict the laws of relativity since you are not moving faster than light in the space around you. Alcubierre showed that the warp drive from “Star Trek” was in fact theoretically possible.

Proxima Centauri here we come, right? Unfortunately, Alcubierre’s method of compressing spacetime had one problem: it requires negative energy or negative mass.

Diagram illustrating how 2 planets of different mass warp a 2D flat grid around them.

This 2–dimensional representation shows how positive mass curves spacetime (left side, blue earth) and negative mass curves spacetime in an opposite direction (right side, red earth). Image via Tokamac/ Wikimedia Commons.

A negative energy problem

Alcubierre’s warp drive would work by creating a bubble of flat spacetime around the spaceship and curving spacetime around that bubble to reduce distances. The warp drive would require either negative mass – a theorized type of matter – or a ring of negative energy density to work. Physicists have never observed negative mass, so that leaves negative energy as the only option.

To create negative energy, a warp drive would use a huge amount of mass to create an imbalance between particles and antiparticles. For example, if an electron and an antielectron appear near the warp drive, one of the particles would get trapped by the mass and this results in an imbalance. This imbalance results in negative energy density. Alcubierre’s warp drive would use this negative energy to create the spacetime bubble.

But for a warp drive to generate enough negative energy, you would need a lot of matter. Alcubierre estimated that a warp drive with a 100-meter bubble would require the mass of the entire visible universe.

In 1999, physicist Chris Van Den Broeck showed that expanding the volume inside the bubble but keeping the surface area constant would reduce the energy requirements significantly, to just about the mass of the sun. A significant improvement, but still far beyond all practical possibilities.

A sci-fi future?

Two recent papers – one by Alexey Bobrick and Gianni Martire and another by Erik Lentz – provide solutions that seem to bring warp drives closer to reality.

Bobrick and Martire realized that by modifying spacetime within the bubble in a certain way, they could remove the need to use negative energy. This solution, though, does not produce a warp drive that can go faster than light.

Independently, Lentz also proposed a solution that does not require negative energy. He used a different geometric approach to solve the equations of General Relativity, and by doing so, he found that a warp drive wouldn’t need to use negative energy. Lentz’s solution would allow the bubble to travel faster than the speed of light.

It is essential to point out that these exciting developments are mathematical models. As a physicist, I won’t fully trust models until we have experimental proof. Yet, the science of warp drives is coming into view. As a science fiction fan, I welcome all this innovative thinking. In the words of Captain Picard:

Things are only impossible until they are not.

Mario Borunda, Associate Professor of Physics, Oklahoma State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: If humanity wants to travel between stars, people are going to need to travel faster than light. New research suggests that it might be possible to build warp drives and beat the galactic speed limit.

Source: Introducing physical warp drives

Source: Breaking the warp barrier: hyper-fast solitons in Einstein–Maxwell-plasma theory

Via The Conversation

The Conversation

Natural radio signal buzzes in Venus’ atmosphere

May 9th 2021 at 08:00

Venus has been in the news a lot since last September, when researchers announced the possible detection of phosphine, a possible life sign, in its atmosphere. On May 3, 2021, NASA’s Parker Solar Probe announced another discovery: a never-before-observed natural low-frequency radio signal in the atmosphere of Venus. The probe, designed primarily to study the sun, came close to Venus to use it as a gravity slingshot, needed to propel the probe sunward. Parker Solar Probe was at its closest to Venus yet – only about 500 miles (800 km) above Venus’ surface on July 11, 2020 – when it found the surprising signal.

The researchers published their new peer-reviewed findings on May 3 in AGU’s Geophysical Research Letters.

Glyn Collinson of NASA’s Goddard Space Flight Center and lead author exclaimed:

I was just so excited to have new data from Venus.

The measurements from Parker Solar Probe are the first new direct measurements of Venus’ atmosphere in nearly 30 years. The results also show that the atmosphere undergoes changes during the sun’s 11-year solar cycle, and that it is now quite different from what it was in the past.

Planet in black and white with many thin streaks around it and stars in the background.

Parker Solar Probe captured this stunning view of Venus’ nightside during its flyby on July 11, 2020. The streaks are cosmic rays and dust particles. Image via NASA/ Johns Hopkins APL/ Naval Research Laboratory/ Guillermo Stenborg and Brendan Gallagher.

How did the spacecraft detect the radio signal?

It did so using its FIELDS instrument, which measures electrical and magnetic fields in the atmosphere. The signal was detected when the spacecraft was closest to the planet, for a period of only seven minutes. Collinson saw it in the data and recognized it, saying:

Then the next day, I woke up. And I thought, ‘Oh my god, I know what this is!’

He had seen the exact same kind of radio signal before from the Galileo orbiter, which had explored Jupiter and its moons. That mission ended in 2003. In this case, the signal, which looked like a thin “frown” in the data, was found in the ionospheres of some of the moons. The similarity of the signal meant that Parker Solar Probe had unexpectedly skimmed through the upper atmosphere of Venus, or more specifically, its ionosphere.

The ionosphere is a region of charged gases or plasma in the upper atmosphere that emits natural radio waves. Galileo had detected those radio waves at Jupiter’s moons, and now Parker Solar Probe had also found them in Venus’ atmosphere. The last time Venus’ ionosphere was measured directly was in 1992 by the Pioneer Venus Orbiter. The sun also happened to be at the peak of its solar cycle at the time.

Four curved squares with bright spots and a fuzzy straight line across all four, on black background.

Parker Solar Probe also took the first-ever complete image of the dust ring that circles the sun along Venus’ orbit. The 4 frames of the image were first captured on August 25, 2019. Image via NASA/ Johns Hopkins APL/ Naval Research Laboratory/ Guillermo Stenborg and Brendan Gallagher.

For a long time afterward, however, there were no more Venus missions that could take new measurements. Instead, scientists relied on Earth-based telescopes, which showed that the ionosphere was changing while the sun’s solar cycle started to wane again and become calmer. During solar minimum, the ionosphere on Venus was at its thinnest.

Now, the new measurements from Parker Solar Probe support the previous findings. The close flyby occurred six months after solar minimum – the least active period on the sun – and the data showed that again, the ionosphere was significantly thinner than it was during solar maximum, the most active period. This confirms that the density of Venus’ ionosphere is directly correlated to the strength of the solar cycle. According to co-author Robin Ramstad:

When multiple missions are confirming the same result, one after the other, that gives you a lot of confidence that the thinning is real.

As outlined in the paper:

On July 11, 2020, NASA’s Parker Solar Probe made a close flyby of Venus. During the 7 minutes around the closest approach, one of its scientific instruments detected low-frequency radio emission of a type naturally generated by planetary ionospheres. By measuring the frequency of this emission, we can directly calculate the density of the ionosphere around Parker, finding it to be far less dense than previous missions have encountered. This supports the theory that the ionosphere of Venus varies substantially over the 11-year solar cycle.

Man in scuba diving gear underwater.

Glyn Collinson at NASA’s Goddard Space Flight Center led the new study that found the radio signal in Venus’ atmosphere. Image via Twitter.

Why is this important?

Scientists want to better understand how Venus changed from a former habitable world, according to the latest research, to the inhospitable inferno we see today. The fact that the planet’s ionosphere thins at solar minimum can provide valuable clues as to how the sun affects Venus’ atmosphere. It is also known that the planet’s ionosphere can “leak” into space. Changes like that can tell scientists how the atmosphere has evolved over time.

The discovery of the radio signal is a fortuitous development, since Parker Solar Probe’s main mission is to study the sun, not Venus. As Parker Solar Probe project scientist Nour Raouafi commented:

The goal of flying by Venus is to slow down the spacecraft so that Parker Solar Probe can dive closer to the sun. But we would not miss the opportunity to gather science data and provide unique insights into a mysterious planet such as Venus.

Parker Solar Probe took some stunning images of Venus during its flyby, which NASA released on February 24, 2021. It also imaged the entire dust ring that orbits the sun along Venus’ orbit, the first time that has ever been accomplished by any spacecraft.

There are no current U.S. missions at Venus, so these close flybys provide a great opportunity to gather more data. As Collinson noted:

To see Venus now, it’s all about these little glimpses.

Colorful, banded thick clouds on a planet in space.

False-color view of Venus (to bring out details) from Japan’s Akatsuki orbiter. The radio signal was detected in Venus’ ionosphere in the upper atmosphere by Parker Solar Probe. Image via JAXA/ ISAS/ Akatsuki Project Team/ Royal Astronomical Society/ CC BY 4.0.

Spacecraft near the sun, which has huge red and yellow solar flares.

Artist’s concept of Parker Solar Probe as it nears the sun during a flyby. The probe detected a low-frequency natural radio signal coming from Venus’ upper atmosphere as it passed by the planet last year. Image via NASA/ Johns Hopkins APL/ Steve Gribben.

Bottom line: NASA’s Parker Solar Probe has detected an unexpected natural radio signal being emitted by Venus’ ionosphere.

Source: Depleted Plasma Densities in the Ionosphere of Venus Near Solar Minimum From Parker Solar Probe Observations of Upper Hybrid Resonance Emission

Via NASA

How do you measure the mass of a star?

May 9th 2021 at 07:31
Large white star to the left, tiny blue star to the right, against a star-strewn background.

Artist’s concept of the binary star system of Sirius A and its small blue companion, Sirius B, a hot white dwarf. The 2 stars revolve around each other every 50 years. Image via ESA/ G. Bacon.

There are lots of binary stars – two stars revolving around a common center of mass – populating the starry sky. In fact, a large majority of all stars we see (around 85%) are part of a multiple star system of two or more stars! This is fortunate for astronomers because two stars together provide an easy way to measure their respective masses.

To find the masses of stars in double systems, you need to know only two things: the semi-major axis or mean distance between the two stars (often expressed in astronomical units, which is the average distance between the Earth and sun), and the time it takes for the two stars to revolve around one another (aka the orbital period, often expressed in Earth-years). With those two observations alone, astronomers are able to calculate the stars’ masses, which they typically do in units of solar masses (that is, a measure of how many of our suns the star “weighs”. One solar mass is 1.989 x 1030 kilograms or about 333,000 times the mass of our planet Earth.).

We will use Sirius, the brightest star of the nighttime sky, as an example. It looks like a single star to the unaided eye, but it, too, is a binary star (and you can see it yourself, if you have a small telescope). The two stars orbit each other with a period of about 50 Earth-years, at an average distance of about 20 astronomical units (AU). The brighter of the two is called Sirius A, while its fainter companion is known as Sirius B (The Pup).

Black background with one central white spot with spikes, and a tiny white dot on its left side.

View at EarthSky Community Photos. | Michael Teoh at Heng Ee Observatory in Penang, Malaysia, captured this photo of Sirius A and Sirius B (a white dwarf) on January 26, 2021. He used 30 1-second exposures and stacked them together to make faint Sirius B appear. Thank you, Michael!

So how would astronomers find the masses of Sirius A and B? They would simply plug in the mean distance between the two stars and their orbital period into the easy-to-use formula below, first derived by Johannes Kepler in 1618, and known as Kepler’s Third law:

Total mass = distance3/period2

Here, the distance is the mean distance between the stars (or, more precisely, the semi-major axis) in astronomical units, so 20, and the orbital period is 50 years.

The resulting total mass is about three solar masses. Note that this is not the mass of one star but of both stars added together. So, we know that the whole binary system equals three solar masses.

Two overlapping elliptical orbits in red with white circles moving around the orbits.

An example of a binary star system, whose component stars orbit around a common center of mass (the red cross). In this depiction, the two stars have similar masses. In the case of the Sirius binary star system, Sirius A has about twice the mass of Sirius B. Image via Wikimedia Commons.

To find out the mass of each individual star, astronomers need to know the mean distance of each star from the barycenter: their common center of mass. To learn this, once again they rely on their observations.

It turns out that Sirius B, the less massive star, is about twice as far from the barycenter than is Sirius A. That means Sirius B has about half the mass of Sirius A.

Thus, if you know the whole system is about three solar masses, you can deduce that the mass of Sirius A is about two solar masses, while Sirius B pretty much equals our sun in mass.

But what about stars that are alone in their star systems, like the sun? The binary star systems are once again the key: Once we have calculated the masses for a whole lot of stars in binary systems, and also know how luminous they are, we notice that there is a relationship between their luminosity and their mass. In other words, for single stars we only need to measure its luminosity and then use the mass-luminosity relation to figure out their mass. Thank you, binaries!

Read more: What is stellar luminosity?

Read more: What is stellar magnitude?

Bottom line: For astronomers, binary star systems are a quite useful tool to figure out the mass of stars.

These 5 multi-star systems have habitable zones

May 9th 2021 at 06:45
Two suns rising over a barren landscape with mountains in the distance.

Artist’s concept of a sunrise on a planet with 2 suns, via Shutterstock.

Planets orbiting in their stars’ Goldilocks zones or habitable zones are not too close and not too far from their stars. They’re in a place where water might exist as a liquid on a rocky planet. We tend to think of a planet in the Goldilocks zone of a single star, similar to Earth in our solar system. But what about multiple star systems? Do habitable zones exist in systems of two, three or more stars? Astronomers from New York University Abu Dhabi and the University of Washington show that it is indeed possible. Using a new mathematical model, they found that at least five such known systems – all within 6,000 light-years of Earth – have stable habitable zones where hypothetical planets could harbor life.

The peer-reviewed study was published in Frontiers in Astronomy and Space Sciences on April 15, 2021, and reported in Frontiers Science News on the same day.

These findings are important because stable habitable zones would greatly increase the chances of life evolving on any planets that orbit within them. As lead author Nikolaos Georgakarakos said:

Life is far most likely to evolve on planets located within their system’s habitable zone, just like Earth. Here we investigate whether a habitable zone exists within nine known systems with two or more stars orbited by giant planets. We show for the first time that Kepler-34, -35, -64, -413 and especially Kepler-38 are suitable for hosting Earth-like worlds with oceans.

Closeup of two stars with dark spots close to each other.

Binary star systems, where two stars orbit each other, are common in our galaxy, and are thought to make up to 3/4 of all star systems. Image via Mark Garlick/ Science Photo Library/ New Scientist.

The astronomers studied nine different multi-star systems, and found five of those – Kepler-34, Kepler-35, Kepler-38, Kepler-64 (PH 1) and Kepler-413 – to be the most likely to contain permanent habitable zones with worlds that could host life. Of those, they found Kepler-35, Kepler-38 and Kepler-64 to offer the most benign environment for possible life.

The five star systems are located at distances between 2,764 and 5,933 light-years from Earth, in the constellations Lyra the Harp and Cygnus the Swan. Kepler-64 has at least four stars orbiting each other (!), and the rest are binary star systems with two stars.

One large and three smaller stars close together, different colors.

The Kepler-64 system, also known as PH-1, has at least 4 stars, and is one of the 5 multi-star systems that could contain habitable planets. Image via Open Exoplanet Catalogue.

It is important to note that while smaller rocky planets haven’t yet been found in these star systems, they are all known to have at least one planet as large as Neptune or bigger. This makes it likely that at least some of them also have smaller planets, since most planetary systems found so far tend to have planets of various sizes, like ours.

Generally, multi-star systems are thought to be less likely to have habitable planets, due to all the intricate gravitational interactions going on, especially those with giant planets. But now this new research shows that some of them could be stable enough for life to originate on habitable zone planets. Co-author Ian Dobbs-Dixon said:

We’ve known for a while that binary star systems without giant planets have the potential to harbor habitable worlds. What we have shown here is that in a large fraction of those systems Earth-like planets can remain habitable even in the presence of giant planets.

This is good news for the prospects of finding life in such systems, since, for example, double star systems are estimated to compose up to 3/4 of all star systems. Our single star sun is actually in a minority.

How did the researchers come to these conclusions? Their work is based on previous studies, with the goal of determining the existence, location, and extent of the permanent habitable zone in binary systems with giant planets. The researchers take various factors into consideration, such as the classification, mass, luminosity and spectral energy distribution of the stars, the added gravitational effect of the giant planet and the geometry of the system; the orbital eccentricity (how narrow an ellipse the orbit is), semi-major axis and period of the hypothetical planet’s orbit. They also look at the intensity of solar radiation from the star hitting the planet’s atmosphere and the planet’s climate inertia, the speed at which the atmosphere responds to changes in irradiation.

By doing this, they determined that those five multi-star systems do indeed have permanent habitable zones. Each zone is between 0.4 and 1.5 astronomical units (AU) wide. One AU is the mean distance between Earth and the sun, about 93 million miles (150 million km).

Other binary star systems are not as promising, however. In the Kepler-453 and Kepler-1661 systems, the habitable zones are estimated to be only about half the size as those of the other five. Two others, Kepler-16 and Kepler-1647, are unlikely to have any potentially habitable planets at all. As noted by co-author Siegfried Eggl:

In contrast, the extent of the habitable zones in two further binary systems, Kepler-453 and -1661, is roughly half the expected size, because the giant planets in those systems would destabilize the orbits of additional habitable worlds. For the same reason Kepler-16 and -1647 cannot host additional habitable planets at all. Of course, there is the possibility that life exists outside the habitable zone or on moons orbiting the giant planets themselves, but that may be less desirable real-estate for us.

Smiling man in suit and tie with Mars rover behind him.

Co-author Siegfried Eggl at the University of Washington. Image via The Grainger College of Engineering.

So which system has the most potential for supporting life? Georgakarakos said:

Our best candidate for hosting a world that is potentially habitable is the binary system Kepler-38, approximately 3,970 light-years from Earth, and known to contain a Neptune-sized planet.

Our study confirms that even binary star systems with giant planets are hot targets in the search for Earth 2.0. Watch out Tatooine, we are coming!

Desert landscape with small domed building, a person walking and two suns near the horizon at double sunset.

Scene from “Star Wars” showing a binary star sunset on the planet Tatooine. While this scenario is not real, the new study says that habitable worlds should be able to exist in binary or other multi-star systems. Image via Disney/ Lucasfilm/ Bad Astronomy.

Habitable worlds are not limited to the habitable zone, however. In our own solar system there are multiple icy moons with subsurface oceans that could potentially be home to some kind of life. Europa, Enceladus and Titan in particular are now prime targets for further exploration. The fact that they are common in our solar system makes it reasonable that similar kinds of moons may also exist in some of these multi-star systems, and elsewhere.

Bottom line: Astronomers have identified five multi-star systems that have stable habitable zones. This means that any rocky worlds that may exist in those zones could be potentially habitable.

Source: Circumbinary Habitable Zones in the Presence of a Giant Planet

Via Frontiers Science News

History of Mars’ habitability preserved in ancient dunes

May 7th 2021 at 08:00
Bare rocky outcrop with horizontal layers.

A butte within the Stimson formation as seen by the Curiosity rover. These rock formations contain preserved remnants of ancient dune fields. Image via NASA/ Imperial College London.

Scientists who study the possibility of life on Mars want to know how habitable the planet might have been millions or billions of years ago. Was Mars ever able to support life as we know it, at least microbial? The evidence from landers, rovers and orbiters over the past few decades has continued to indicate that Mars was indeed once more habitable than it is now. But then conditions changed; the water on the surface dried up and the atmosphere became thinner and drier. Late last month, an international team of researchers reported on a new study documenting the changing habitability of Mars. These scientists examined ancient sand dune fields preserved in rocks in Gale Crater, where the Curiosity rover has been exploring an ancient lakebed since 2012.

The new peer-reviewed research was published in AGU’s JGR: Planets on March 31, 2021.

Curiosity had already confirmed that Gale Crater used to be a lake or series of lakes a few billion years ago. Now, it has also found evidence for an ancient dune field – called the Stimson formation – that is still preserved as a layer of rocks that lies on top of the older lake bottom rock layers.

Two maps with color-coded terrains and text annotations.

This is the region the Curiosity rover has been exploring over the past several years, near the base of Mount Sharp in Gale Crater. The Stimson formation outcrops are marked with a square. Image via NASA/ JPL/ University of Arizona/ Imperial College of London.

This change in rock layers provides clues as to how the climate changed and how the environment shifted from a habitable one to the uninhabitable arid desert we see today.

It also helps scientists better understand various surface and atmospheric processes that were active at the time, such as the direction of the blowing sand that formed the dunes. The researchers were even able to figure out the shape, size and migration direction of the largest dunes.

One discovery is that there were once dunes nestled right up against the central mountain in Gale Crater, called Mount Sharp. They had formed on a wind-eroded surface at a 5 degree angle. Those dunes were what are known as compound dunes; each large dune had its own set of smaller “satellite” dunes that migrated in different directions from the main dunes. From the paper:

Analysis of the sedimentary structures generated by the complex interaction of these two scales of dune indicates that the large dunes migrated north, and that the smaller superimposed dunes migrated across the faces of the large dunes toward the northeast.

Dunes are of course common Earth, and they are on Mars as well. Mars has vast dune fields today, not just the ancient preserved ones from billions of years ago. Steve Banham, lead author of the new study, discussed how such dunes form and how they can be preserved:

As the wind blows, it transports sand grains of a certain size, and organizes them into piles of sand we recognize as sand dunes. These landforms are common on Earth in sandy deserts, such as the Sahara, the Namibian dune field, and the Arabian deserts. The strength of the wind and its uniformity of direction control the shape and size of the dune, and evidence of this can be preserved in the rock record.

If there is an excess of sediment transported into a region, dunes can climb as they migrate and partially bury adjacent dunes. These buried layers contain a feature called ‘cross-bedding,’ which can give an indication of the size of the dunes and the direction which they were migrating. By investigating these cross beds, we were able to determine these strata were deposited by specific dunes that form when competing winds transport sediment in two different directions.

It’s amazing that from looking at Martian rocks we can determine that two competing winds drove these large dunes across the plains of Gale Crater three and a half billion years ago. This is some of the first evidence we have of variable wind directions, be they seasonal or otherwise.

Four horizontal images of rock layers with text annotations.

Butte M1b, part of the Murray buttes within the Stimson formation, showing undulating rock layers, thought to be the remains of ancient sand dunes. Image via Banham et al./ JGR: Planets.

Horizontal gray rock layers with a lot of thin yellow horizontal lines and labels.

Another view of thin rock layers in the Murray buttes within the Stimson formation. Image via Banham et al./ JGR: Planets.

The dune fields are thought to have formed after the lake in Gale Crater dried out. The bottom of the crater, and lower flanks of the mountain, are composed of ancient lakebed sediments. Higher up on Mount Sharp are non-sedimentary sandstone rock layers. Most of Curiosity’s mission so far has been spent examining the sedimentary layers, containing mudstones and clays, for evidence of past habitability. Banham added:

More than 3.5 billion years ago this lake dried out, and the lake bottom sediments were exhumed and eroded to form the mountain at the center of the crater, the present-day Mount Sharp. The flanks of the mountain are where we have found evidence that an ancient dune field formed after the lake, indicating an extremely arid climate.

While analysis of the preserved dune fields helps to answer questions about the changing habitability of Mars, it also appears to indicate that the habitability potential lessened when the dunes were formed, after the lake dried up. When the dunes formed, there was less water available for any microbes, and the landscape was starting to change to the dry desert we see today. The dunes would also not be ideal for preserving traces of any past life, either. From the paper:

The presence of large, wind-driven dunes indicates that the region was extremely arid, and that – at the time the Stimson dune field existed – the interior of Gale Crater was devoid of surface water, unlike the setting recorded by the older, underlying lake sediments of the Murray formation.

Smiling young man with rocky hills behind him.

Steven Banham at Imperial College London is the lead author of the new study about ancient Martian sand dunes. Image via Imperial College London.

Banham said:

The vast expanse of the dune field wouldn’t have been a particularly hospitable place for microbes to live, and the record left behind would rarely preserve evidence of life, if there was any.

This desert sand represents a snapshot of time within Gale Crater, and we know that the dune field was preceded by lakes, yet we don’t know what overlies the desert sandstones further up Mount Sharp. It could be more layers deposited in arid conditions, or it could be deposits associated with more humid climates. We will have to wait and see.

Banham added:

Although geologists have been reading rocks on Earth for 200 years, it’s only in the last decade or so that we’ve been able to read Martian rocks with the same level of detail as we do on Earth.

Curiosity is now continuing to drive further up the flanks of Mount Sharp, and will study rock layers higher up to document any changes in ancient wind patterns, Banham said:

We’re interested to see how the dunes reflect the wider climate of Mars, its changing seasons, and longer-term changes in wind direction. Ultimately, this all relates to the major driving question: to discover whether life ever arose on Mars.

Sand dunes and rocks in black and white.

Dune fields are still common on Mars, such as this one seen by the Viking 1 lander on August 3, 1976. Image via NASA/ JPL-Caltech.

Large sand dune in rocky terrain with hills in background.

Closeup view of a sand dune called Namib Dune, part of the Bagnold Dunes near Mount Sharp in Gale Crater, as seen by the Curiosity rover on December 18, 2015. Namib is about 16 feet (5 meters) tall. Image via NASA/ JPL-Caltech/ MSSS.

Mars’ atmosphere is substantially thinner today then it was back then, but the planet still has active dune fields. All of the rovers and landers have seen dunes, as well as smaller ripples, up close. Orbiters have photographed them all over the planet, including at the poles. The dunes come in a variety of shapes and sizes, and often closely resemble dunes and dune fields on Earth. Just as it is often described to be, Mars truly is a desert world.

Bottom line: The changing habitability of Mars has been preserved in ancient dune fields in Gale Crater according to a new study from researchers at Imperial College London.

Source: A Rock Record of Complex Aeolian Bedforms in a Hesperian Desert Landscape: The Stimson Formation as Exposed in the Murray Buttes, Gale Crater, Mars

Via Imperial College London

Mars might support microbial life, deep underground

May 7th 2021 at 06:07
A dark mine with a man in an orange coverall and with a brilliant light on his helmet.

Planetary scientist Jesse Tarnas of Brown University and NASA’s Jet Propulsion Laboratory led a new study on the possibility of microbial life beneath the surface of Mars. Here he is at the Kidd Creek Mine in Canada, sampling groundwater 1.5 miles (2.4 km) underground. Image via University of Toronto Stable Isotope Laboratory/ Jesse Tarnas.

Has life ever existed on Mars? Could there still be life somewhere on the planet today? Those are still unanswered questions, but growing evidence over the past few decades has suggested that ancient Mars was quite habitable, at least for microscopic organisms. Evidence for the possibility of the existence present-day Martian life has also increased.

A new study from scientists at Brown University suggests that the Martian subsurface might be a good place to look for possible present-day microbial life on the planet. It’s an idea that has also been suggested in in other studies, but the new research, published April 15, 2021, in the peer-reviewed journal Astrobiology, finds evidence that rocks below the planet’s surface could produce the same kinds of chemical energy that sustain microbial life underground on Earth.

The scientists came to this tentative but tantalizing conclusion after studying Martian meteorites, pieces of Martian rock that eventually landed on Earth after being blasted off Mars’ surface by impacts. By analyzing the chemical composition of the meteorites, the researchers determined that if those rocks were in continuous contact with water, they would produce the same kind of chemical energy that supports microbial communities below the surface on Earth.

Cutaway view of layered rocky terrain with blue inclusions between layers.

Artist’s illustration of subsurface lakes on Mars. Such lakes, or groundwater, would be the best place to search for current Martian life, according to the new study. Chemical interactions with rocks in the crust would provide all the ingredients necessary to sustain microbial ecosystems. Image via NASA/ JPL/ Science Focus.

The results are exciting since the rocks are thought to represent a wide swath of the Martian crust. Jesse Tarnas, a postdoctoral researcher at NASA’s Jet Propulsion Laboratory who led the study, said in a statement:

The big implication here for subsurface exploration science is that wherever you have groundwater on Mars, there’s a good chance that you have enough chemical energy to support subsurface microbial life. We don’t know whether life ever got started beneath the surface of Mars, but if it did, we think there would be ample energy there to sustain it right up to today.

Tarnas led the study while completing his Ph.D. at Brown University.

The possibility of present-day life may then be dependent on there being groundwater or other subsurface water on Mars. We know from rover and orbital missions that there is ample evidence for groundwater in Mars’ past, but what about now?

The researchers say that there should be groundwater in places on Mars even now, and indeed, the first evidence for subsurface water on Mars was found in 2018. The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument on the Mars Express orbiter found evidence for a 12.5-mile wide (20-km wide) lake beneath the ice at the Martian south pole. The water is thought to be kept liquid by salts and pressure from the ice above it. In October 2020, three more smaller but similar lakes close to the first one were also announced.

Despite the cold subsurface environment, such lakes or other groundwater could potentially still support life today, if it ever started. In similar conditions on Earth, vast biomes exist completely separated from the world above on the surface. The microbes in these biomes use the byproducts of the chemical reactions for energy, despite the lack of sunlight. Biomes are defined as “the world’s major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment.”

Cutaway view with machine on surface drilling straight down through many layers of rock.

To search for present-day life on Mars, some experts believe we should drill deep underground, as in this artist’s concept. Image via NASA/ JPL/ NBC News.

How do those reactions happen?

They occur when rocks below the surface come into contact with water. Radiolysis, for example – the dissociation of molecules by ionizing radiation – happens when radioactive elements within rocks react with water trapped in pores and fracture spaces. The chemical reaction breaks the water molecules into hydrogen and oxygen. The hydrogen dissolves in the remaining groundwater, while the oxygen is soaked up by minerals such as pyrite (also known as fools gold). This forms sulfate minerals. One prime location for this kind of chemical activity is the Kidd Creek Mine in Ontario, Canada.

This is great for microbes, which consume the hydrogen for fuel, and use the oxygen to “burn” the fuel.

Microbial ecosystems such as this have been found on Earth more than a mile (1.6 km) deep underground, where the water has never seen sunlight for more than a billion years. These organisms are known as sulfate-reducing microorganisms.

Since these environments are common on Earth, could they also exist on Mars? The researchers decided to look for evidence of similar radiolysis habitats beneath the Martian surface. They combined data from the Curiosity rover, orbiters and directly from the meteorites. They searched specifically for radioactive elements like thorium, uranium and potassium, along with sulfide minerals that could be converted to sulfate. The researchers also wanted to see if the rocks had enough pore space to hold liquid water.

Black and white horizontal lines with short horizontal streak of blue, features labeled.

Radar image from Mars Express in 2018 showing the first detected largest lake beneath the south polar ice. Image via ESA/ NASA/ JPL/ ASI/ Univ. Rome/ R. Orosei et al. 2018.

The results were very encouraging. All the necessary ingredients were found, in enough abundance, in several types of Martian meteorites. Older rocks like regolith breccias were found to be the most likely to be able to support microbial life. Those rocks from Mars’ crust are more than 3.6 billion years old.

If there is a good chance of microbial life beneath Mars’ surface today, then how do we look for it?

You would need to dig a lot deeper than any rover or lander has before, using a small drill probe, according to the researchers. It would be challenging, but not impossible. If such an endeavor were to actually find life, it would then of course be well worth the effort. Co-author Jack Mustard at Brown University said:

The subsurface is one of the frontiers in Mars exploration. We’ve investigated the atmosphere, mapped the surface with different wavelengths of light and landed on the surface in half-a-dozen places, and that work continues to tell us so much about the planet’s past. But if we want to think about the possibility of present-day life, the subsurface is absolutely going to be where the action is.

A similar study from Rutgers University reported on in December 2020 also recommended looking deep underground for any Martian microbes. That study focused on how geothermal heat could melt subsurface ice.

Wiggly contour lines around four bluish-colored patches.

In 2020, the discovery of three more subsurface lakes was announced, adjacent to the first larger one beneath the South Pole (in blue here). This is a radar map from Mars Express. Could there still be groundwater elsewhere on Mars also? Image via ESA/ Ars Technica.

NASA’s Perseverance rover has just started its mission to search for signs of ancient life in an ancient river delta, and ESA’s ExoMars rover Rosalind Franklin will soon launch to look for evidence of life as well. The rover can drill deeper than Perseverance, about 2 meters, although probably still not enough to reach any groundwater that may exist below. These are the first missions since the Viking landers in the late 1970s/early 1980s that are designed specifically to look for life (with mixed results still debated today). Up until now, most other rovers and landers have focused on finding evidence for habitable conditions on ancient Mars, which they have done, in spades.

If Tarnas and his colleagues are right, then to find current life, we need to look underground. The old adage of Mars exploration may well turn out to be right after all: to look for life, follow the water.

Bottom line: Mars has the right ingredients for current subsurface microbial life, according to a new study from Brown University.

Source: Earth-like Habitable Environments in the Subsurface of Mars

Via Brown University

Read more: SETI’s Nathalie Cabrol on modern-day Mars life, underground

Read more: Active volcanoes on Mars today? If so, they may point to Mars habitability

The fiery fate of China’s Long March 5B rocket

May 10th 2021 at 12:00
Two panels with bright dashed lines against cloudy sky.

View at EarthSky Community Photos. | Filipp Romanov in Yuzhno-Morskoy, Russia, caught the Long March rocket booster on May 5 and May 6, 2021. He said: “I observed Long March 5B rocket body … on May 5, 2021 (18:38 UT) and on May 6, 2021 (18:18 UT) from my small homeland. On the first night it fast passed high in the sky with periodic bright flares (up to 0m), but cloudiness slightly interfered with the observation. On the second night, it looked less bright due to the lower altitude above the horizon, but regular flares were clearly visible.”

The core stage of China’s 100-foot (30-m) Long March 5B rocket – which launched the Tianhe space station module on April 29, 2021 – plummeted into the Indian Ocean near the Maldives late Saturday, May 8. It was one of the largest-ever pieces of space debris to make an uncontrolled re-entry back into Earth’s atmosphere. And while, luckily, there were no casualties, sightings and videos were circulating social media platforms as the rocket began its final orbits around Earth. According to China’s Manned Space Engineering Office, the country’s spaceflight agency, the core stage fell around longitude 72.47 degrees east and latitude 2.65 degrees north.

Also on May 8, new NASA Administrator Sen. Bill Nelson, who was sworn in earlier this month, released a rare statement criticizing China’s handling of the re-entry of the Long March 5B rocket:

Spacefaring nations must minimize the risks to people and property on Earth of re-entries of space objects and maximize transparency regarding those operations.

It is clear that China is failing to meet responsible standards regarding their space debris.

It is critical that China and all spacefaring nations and commercial entities act responsibly and transparently in space to ensure the safety, stability, security, and long-term sustainability of outer space activities.

Variables such as atmospheric fluctuations meant re-entry prediction windows spanned days earlier in the week, and narrowed into a two-hour window around four before expected re-entry. While most of the stage burned up, components made of heat resistant materials – such as tanks and thrusters made of stainless steel or titanium – likely made it to the ocean surface. Most returning space debris does fall into an ocean since Earth’s oceans cover 70% of our planet. In this case, the China Manned Space Engineering Office said in a post on WeChat that the rocket debris crashed to the ocean just west of the Maldives. It was unclear if any debris had landed on the atoll nation.

1/x
I updated my blogpost on the Chinese #CZ5B #reentry with a new GMAT analysis:https://t.co/MrsQ0fA1J2
I fiddled with the area-to-mass ratio in GMAT untill I got a splashdown close to the time and location reported by China. I then looked what (cont.) pic.twitter.com/5HM1ruBHVB

— Dr Marco Langbroek ? #Vaccinate (@Marco_Langbroek) May 9, 2021

On the CZ-5B core stage re-entry, I missed this interesting image before, the Italian MoD used its MFDR-LR Doppler radar to track it, and show it was tumbling…

image via @EU_SST pic.twitter.com/6eqv9r5nak

— DutchSpace (@DutchSpace) May 9, 2021

According to Mark Matney, a scientist in the Orbital Debris Program Office at NASA’s Johnson Space Center in Houston, the odds that an individual will be hit by falling space debris are one in several trillion. However, falling space debris does have the potential to create harm to property and living things.

Even for experts, plotting the precise trajectory of a large piece of falling space debris is difficult, if not impossible. There were many uncertainties involved in calculating the effect of atmospheric drag on China’s core module, for example. The high speed of the rocket body means it orbited Earth roughly every 90 minutes, and so a change of just a few minutes in re-entry time resulted in a re-entry point hundreds of miles away. Plus, the sun is now in a relatively active phase of its 11-year cycle, and Earth’s atmosphere can expand or contract with solar activity. All of these factors made it hard to estimate exactly when and where the rocket would come down.

The week leading up to the re-entry was filled with speculation on Twitter and elsewhere. Astrophysicist Jonathan McDowell of Harvard University (@planet4589 on Twitter) had been regularly tweeting about the descending core stage. In a separate statement, McDowell predicted some pieces of the rocket would survive re-entry and that it would be the:

… equivalent of a small plane crash scattered over 100 miles … Last time [China] launched a Long March 5B rocket, they ended up with big long rods of metal flying through the sky, damaging several buildings in the Ivory Coast.

A slightly elongated bright spot on an otherwise blank gray field, with text below.

The image above comes from a single half-second exposure, remotely taken with the Elena robotic unit of the Virtual Telescope on May 6, 2021. The telescope tracked the exceptionally fast (0.3 deg/second) apparent motion of the object. Gianluca Masi of Virtual Telescope Project wrote: “At the imaging time, the rocket stage was at about 700 km [400 miles] from our telescope, while the sun was just a few degrees below the horizon, so the sky was incredibly bright: these conditions made the imaging quite extreme, but our robotic telescope succeeded in capturing this huge debris.” Image via Virtual Telescope.

Interestingly, the return of China’s Long March 5B came just days after the new Spaceflight Assets bill was affirmed by Florida’s legislature on April 26, 2021. The bill, which had the support of SpaceX, is now awaiting the signature of Florida governor Ron DeSantis. When enacted, the law will go into effect on July 1, and require that anyone who finds “reasonably identifiable” spacecraft parts – in and around Florida at least – must report them to local law enforcement and that the authorities must then make a “reasonable effort” to notify the hardware’s owner. The bill grants entities involved in launching rockets and spacecraft, such as SpaceX, access to private property, if necessary, to recover discarded space-related artifacts. Anyone failing to surrender such artifacts could be charged with “misappropriation of a spaceflight asset,” a first-degree misdemeanor, punishable by up to a year in prison or a $1,000 fine. Violators may even pay additional restitution if the hardware is lost or damaged.

Read more from EarthSky: Florida bill says companies like SpaceX retain ownership of fallen hardware

We have Salyut 7's parts for display here in Argentina.
In Oro Verde Observatory you can see part of the hatch and same electronics. The hatch is outside the main entry.https://t.co/uIhsRLPYEJ pic.twitter.com/3gZcVhQtMx

— Guillermo García (@AstroLepra) May 9, 2021

In Casilda, Santa Fe, near Rosario, my city, we have a small Salyut 7's fuel tank for display in the Museo y Archivo Histórico Municipal.
That tank fell to ground 220 km. "before" the hatch. pic.twitter.com/wWAFgMExQF

— Guillermo García (@AstroLepra) May 9, 2021

China, our world’s most populous country, hopes to have its new space station operational by 2022. The only space station currently in orbit is the International Space Station (ISS); China is not an ISS partner, and no Chinese nationals have been aboard. The Chinese government sat out the famous 1960s space race between the Soviet Union and the U.S., which ultimately launched the first humans to the moon in 1969. But, in recent years, China has been making up for lost time. It’s launched several robotic missions to the moon and Mars, as well as successfully landed on the moon’s far side, and made history with its lunar sample return mission. Tianwen-1 is a Chinese probe that entered Mars orbit on February 10, 2021; it’s set to land a rover on Mars’ surface this month or in June.

Meanwhile, the Tianhe module will become the living quarters of the future Chinese Space Station. It’s currently in its correct orbit after separating from the core stage of the rocket as planned.

Read more from EarthSky: Chinese rover Zhurong to attempt a Mars landing this month

The long Chinese rocket blasts off into a cloudy sky with a burst of fire beneath it.

April 29, 2021, liftoff of the Long March 5B rocket carrying the Tianhe core module for the Chinese Space Station. The core stage re-entered Earth’s atmosphere on May 8, 2021. Image via CCTV/ SpaceNews.

Bottom line: China’s Long March 5B rocket – which successfully launched the Tianhe space station module on April 29, 2021 – underwent an uncontrolled re-entry back into Earth’s atmosphere, ultimately landing on May 8 in the Indian Ocean just west of the Maldives.

Via SpaceNews

Chinese rover Zhurong to attempt to land on Mars this month

May 6th 2021 at 06:23
A boxy spacecraft standing on legs on barren red dirt with tracks for a rover to roll down.

Artist’s concept of Chinese spacecraft on Mars. Image via Xinhua/ The Conversation.

By Deep Bandivadekar, University of Strathclyde

For the first few months of 2021, the Martian atmosphere was buzzing with new visitors from Earth. In February, both the UAE Space Agency’s Hope probe and China’s Tianwen-1 entered Mars’ orbit.

On February 19, NASA landed the Perseverance rover with its companion, the Ingenuity helicopter, both of which have been setting new milestones since.

The next visitor to the planet will be Tianwen-1 mission’s rover Zhurong, which will attempt to reach the surface of Mars in mid-May. To enter the Martian atmosphere, it will use a slightly different technique from previous missions.

Landing on Mars is notoriously dangerous. More missions have failed than succeeded. A successful Mars landing requires entering the atmosphere at very high speeds, then slowing the spacecraft down just the right way as it approaches its landing location.

This phase of the mission, known as entry-descent-landing, is the most critical. Previous missions have used several different ways of Martian atmospheric entry.

Perfecting entry to Mars’s atmosphere has been helped by the experience of returning spacecraft to Earth. Earth may have a significantly different atmosphere from Mars, but the principles remain the same.

A spacecraft orbiting a planet will be moving very fast, to keep itself bound to that orbit. But if the spacecraft entered an atmosphere at such high speed, even one as thin as Mars’s, it would burn up. Anything entering the atmosphere needs to be slowed down significantly and to get rid of the heat generated during this brief journey. There are several ways to go about it.

Spacecraft are protected from the heat generated during atmospheric entry using heat shields. Various missions in the past have used techniques such as absorbing heat, an insulating coating, reflecting the heat back into atmosphere or by ablation, burning up the shield material.

From Apollo missions of 1960s to the more recent SpaceX’s Dragon, these techniques have been used successfully, and they work really well for Earth. But when it comes to Mars, engineers need to employ some additional measures.

A white rocket launching with fire below and billowing clouds of steam.

A rocket carrying the rover launched in July 2020. Image via ITAR-TASS News Agency/ Alamy Stock Photos/ The Conversation.

Landing on Mars

Orbiters are designed to monitor a planet’s surface from the orbit and act as a communications relay station. When approaching a planet, the spacecraft is usually directed along successively smaller elliptical orbits, slowing down each time, until it reaches its target orbit. This technique can also be used to lower the orbit of a spacecraft ahead of a lander’s atmospheric entry.

The entire maneuver occurs over a few months and doesn’t need any additional equipment: an efficient way to conserve fuel. Since it uses the planet’s upper atmosphere to apply brakes, it’s called as aerobraking. Aerobraking has been used for various Mars missions including ExoMars Trace Gas Orbiter and the Mars Reconnaissance Orbiter.

Aerobraking can significantly slow down the spacecraft, but for missions with rovers to land it gets more complicated. On Mars, the atmospheric density is just 1% of Earth’s and there are no oceans for the spacecraft to safely splash into. The blunt shape of the spacecraft alone is not enough to reduce the speed.

Previously, successful missions have used extra measures. Mars Pathfinder spacecraft used parachutes to decelerate, while relying on a unique airbag system that sprang into action in the final few seconds to absorb the landing shock. The Spirit and Opportunity rovers landed successfully on Mars with the same technique.

A few years later, Curiosity rover used a new landing system. In the final few seconds, rockets were fired, allowing the spacecraft to hover while a tether – a skycrane – lowered the rover to the dusty Martian surface. This new system demonstrated delivery of a heavy payload to Mars and paved the way for bigger missions.

More recently, the Perseverance rover, which landed in early 2021, used the the reliable skycrane as well as two more advanced technologies. These new features, which used live images taken from its cameras, enabled a more accurate, reliable and safer landing.

Zhurong: the ‘fire-god’

The Chinese Tianwen-1 rover landing is the next Mars mission. The ambitious mission has orbiting, landing and roving components – the first mission to include all three on its first attempt. It has already been circling the red planet since it entered Mars’ orbit on February 24 and will attempt to land its rover Zhurong – which means “fire god” – in mid May.

In size, Zhurong falls between Spirit and Perseverance and it is carrying six pieces of scientific equipment. After landing, Zhurong will survey the surroundings to study Martian soil, geomorphology and atmosphere, and will look for signs of subsurface water ice.

Traditionally, the Chinese authorities don’t reveal a lot of information before the event. However, based on an early overview of the mission by some Chinese researchers, we know the landing sequence the spacecraft will attempt to follow.

On May 17, Zhurong – protected by an aeroshell (a protective shell surrounding the spacecraft which includes the heat shield) – will enter the atmosphere at a speed of 4 km/s [about 9,000 mph]. When it slows down enough, parachutes will be deployed. In the last phase of the sequence, rockets with variable thrust engines will be used for further deceleration.

In contrast with its American counterpart, Tianwen-1 will employ two reliable technologies: a laser range finder to work out where it is relative to Martian terrain and a microwave sensor to determine its speed more accurately. These will be used for navigational correction during its parachuted descent phase. During the powered descent phase at the end, optical and Lidar imaging will assist in hazard detection.

Just before touchdown, an automated obstacle avoidance sequence will begin for soft landing. If the mission is successful, China will be the first country to land a rover on Mars in its first attempt. A few days after that, Zhurong will be ready to explore the surface.

Deep Bandivadekar, Ph.D. candidate, University of Strathclyde

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: The Chinese Tianwen-1 mission’s Zhurong rover will attempt to land on the surface of Mars in mid-May 2021.

The Conversation

NASA expects upcoming space telescope to find 100,000 new worlds

May 6th 2021 at 06:06
Dark planet in front of its much larger bright star.

Artist’s concept of an exoplanet transiting in front of its star. The upcoming Roman space telescope mission is expected to find at least 100,000 new such transiting worlds. Image via ESA.

Since the 1990s, astronomers have discovered more than 4,000 exoplanets – planets outside our solar system, orbiting other stars. NASA’s upcoming Roman Space Telescope – named for American astronomer Nancy Grace Roman – is one of the next generation of space telescopes that will play a big part in discovering more new worlds. In fact, NASA is expecting Roman, which is scheduled to launch in the mid-2020s, to discover upwards of 100,000 exoplanets, the space agency announced on March 31, 2021.

How will Roman do this? The telescope will use two different methods for detecting exoplanets, the transit method and microlensing. Most telescopes use primarily just one method, but by using two different ones, Roman – previously known as the Wide Field Infrared Survey Telescope (WFIRST) – will be one of the most prolific planet hunters ever launched.

Microlensing uses the gravitational light-bending effects of massive objects to detect planets orbiting a star. It does this by monitoring the tiny changes in light produced by the star. This happens when a more distant star happens to align with the closer foreground star, the one that is being studied for the presence of possible planets. The closer star acts as a sort of lens, bending the light coming from the further star. As the alignment changes slightly over days and weeks, due to the movement of the stars, the brightness of the more distant star changes slightly also. By looking at the pattern of changes in the light of the closer target star, astronomers can find clues as to there are any planets orbiting it.

Wide, foil-covered open-ended cylinder in space with stars in background.

The Nancy Grace Roman Space Telescope, as seen in this artist’s illustration. Image via NASA/ GSFC/ Hubblesite.

This kind of microlensing event doesn’t happen often, however, so Roman will also search for planets using the most common technique, the transit method. As Ben Montet, a Scientia Lecturer at the University of New South Wales, said in a statement:

Microlensing events are rare and occur quickly, so you need to look at a lot of stars repeatedly and precisely measure brightness changes to detect them. Those are exactly the same things you need to do to find transiting planets, so by creating a robust microlensing survey, Roman will produce a nice transit survey as well.

Most of Roman’s discoveries should come from the transit method. Montet says that the telescope should be able to find 100,000 planets, or more, transiting in front of their stars. Montet previously published a paper in 2017 detailing what Roman should be able to accomplish, when it was called WFIRST.

In such transits, the brightness of the host star dims very slightly as a planets transits in front of it, as seen from Earth. By measuring the changes in light, scientists can determine to some accuracy how large a planet is. Follow-up observations can often help determine the mass of the planet and how large its orbit is.

While the transit method is expected to find many more planets than microlensing, both methods are complementary to each other. Many exoplanets have been found orbiting very close to their stars, such as hot Jupiters, and the transit method is better suited for finding those kinds of planets. Microlensing, on the other hand, is more useful for detecting planets orbiting farther away from their stars. It can even find rogue planets, ones that don’t orbit any star at all, and are just floating around freely in interstellar space! The combination of the two methods will also help scientists find exoplanets with a wide variety of sizes and orbits.

According to Jennifer Yee, an astrophysicist at the Center for Astrophysics | Harvard & Smithsonian:

The fact that we’ll be able to detect thousands of transiting planets just by looking at microlensing data that’s already been taken is exciting. It’s free science.

What kinds of planets will Roman discover?

Most, about 3/4, will probably be gas giants similar to Jupiter and Saturn. Also ice giant type worlds, like Uranus and Neptune, are expected to be among those. Most of the rest may be mini-Neptunes, four to eight times the mass of Earth. Mini-Neptunes are a bit larger than super-Earths, which are a little larger and more massive than Earth.

Milky Way galaxy with green and blue beams coming from, and a small red circle around, the location of Earth, with text.

Comparison of exoplanet search areas for three different space telescopes: Roman space telescope, TESS and Kepler. Roman will peer deeper into our galaxy than any previous mission. Image via NASA/ Goddard Space Flight Center.

Some of these planets will likely be within the habitable zones of their stars, the region where temperatures could allow water to remain liquid on the surfaces of rocky worlds.

Roman will cover new celestial territory and look deeper into our galaxy than ever before. It will be able to find planets up to 26,000 light-years away. By comparison, the Kepler Space Telescope, which has now finished its mission, studied stars up to 2,000 light-years distant on average, and TESS currently focuses on looking for planets up to about 150 light-years away.

Missions like Kepler and TESS, as well as Earth-based telescopes, have already discovered a wide variety of worlds in the small regions of our galaxy examined so far. These range from rocky planets about the size of Earth and a bit smaller, to gas giant worlds larger than Jupiter. It will be exciting to see what kinds of new worlds that Roman finds.

Smiling man with eyeglasses and beard and green shirt.

In 2017, Ben Montet at the University of New South Wales published a paper outlining what Roman will be able to accomplish. Image via UNSW.

Roman was named after Nancy Grace Roman (1925-2018), NASA’s first chief astronomer, who paved the way for space telescopes focused on studying the broader universe. She is also considered to be the “mother” of the beloved Hubble Space Telescope. Thomas Zurbuchen, NASA’s associate administrator for science, said:

Nancy Grace Roman was a leader and advocate whose dedication contributed to NASA seriously pursuing the field of astrophysics and taking it to new heights. Her name deserves a place in the heavens she studied and opened for so many.

Bottom line: NASA’s upcoming Roman space telescope mission is expected to find at least 100,000 new exoplanets orbiting other stars, according to astronomers.

Via NASA

Photos from 2021’s Eta Aquariid meteor shower

May 5th 2021 at 14:10
Long, thin greenish streak of light in dark sky above Southwestern-style building.

View at EarthSky Community Photos. | Eliot Herman captured this photo of an Eta Aquariid meteor from Tucson, Arizona. He wrote that he captured it at: “…1:48 am on peak night [morning of May 5, 2021]. The radiant is still below the horizon, resulting in this long-trail meteor with the beautiful green, typical of Halley’s comet-derived meteors. My backyard view.” Thank you, Eliot!

Cloudy stretch of Milky Way across starry sky with long thin streak high above horizon.

View at EarthSky Community Photos. | Mary Jo Machnica in Hamburg, New York, captured this photo of an Eta Aquariid on May 6, 2021. She wrote: “I knew that the Eta Aquariid meteor shower was going to peak this morning. I took a nap, not setting my alarm. If I was awoken I would go out. 3 was peak viewing. I awoke at 2 am. Ezra and I head out. Not going too far from home. I knew there was going to be a ton of light pollution. But, it didn’t matter. I just needed to be under the stars. Needing to feel small. Needing to know that the G-d of the Universe is in control of everything. Getting there right before 3 am, I set up my camera. Super damp out! Glad I have my lens warmer. With everything set up, I just keep taking photo after photo hoping to capture a glimpse of a meteor. I see a couple meteors with my eyes, but they don’t show up in the photo … That’s okay. I keep snapping away,talking out loud to the Creator of the Universe, just Ezra and I. As I was talking, this shot was taken.” Thank you, Mary Jo!

Nearly vertical star cloud with small streak of white.

View at EarthSky Community Photos. | Chicky Leclair in Vanderpool, TX, captured this photo of an Eta Aquariid on May 6, 2021. He wrote: “Drove out to class 3 dark sky to shoot the Milky Way and caught one of the meteors.” Thank you, Chicky!

Blue background with short, thin streak of light blue against scattered stars.

View at EarthSky Community Photos. | Kathie O’Donnell in Rapid City, South Dakota, captured this photo of an Eta Aquariid slicing through the Big Dipper on May 4, 2021. She wrote: “On the hunt for Eta Aquariids from the back porch again. I witnessed one meteor around 12:18 a.m. GoPro picked this one up at 2:57 a.m., followed by another one at 4:04 a.m. May the 4th be with you!” Thank you, Kathie!

Bottom line: The Eta Aquariid meteor shower peaks from May 3 through May 6 in 2021, and readers are sending us their best photos. If you have a great shot to share, send it to EarthSky Community Photos!

Map of Milky Way halo reveals dark matter ocean

May 5th 2021 at 08:00

Astronomers observed distant stars in the faint halo surrounding our Milky Way galaxy and have now created a map of the halo, the first of its kind of these outermost parts of our galaxy. These new observations, the astronomers said in April 2021, show how the Large Magellanic Cloud – one of the Milky Way’s satellite galaxies – has created a wake, like a ship sailing through calm waters, as it travels through the Milky Way’s halo. The wake shows up as a distinct bright pathway of stars on the map, telling us that the Magellanic Clouds are still traveling in their very first orbit around the Milky Way galaxy. And the wake itself may be made up of dark matter, dragging the stars along with it!

The discovery was published in the peer-reviewed journal Nature on April 21.

There are many interesting things about galactic haloes. They are faint and hard to observe, extend to large distances out from their galaxies and are – apart from a few stars, gas and dust – thought to contain a large amount of dark matter. Dark matter is called “dark” not only because we know little about it, but because it does not reveal its existence to us through light, only through gravitational interaction with other matter. The video above illustrates how far out from our galaxy’s main disk the halo stretches, as well as the pathway – the wake – of the Large Magellanic Cloud traveling through it.

Oval filled with swirly blue colors, with a horizontal stripe and a bulge of stars, and two small irregular galaxies, all labeled.

The new map of the Milky Way’s halo (blue elliptical region) with the disk of the Milky Way galaxy, seen from the side, and with the satellite galaxy the Large Magellanic Cloud in the bottom right (the small one is there too). What is interesting in this image are the bright areas in the halo: the lower one forms a distinct pathway – a wake – behind the Large Magellanic cloud. The top one is a region of more stars in the northern hemisphere of the halo. Both of these halo anomalies were first predicted by computer models and have now been observationally confirmed. Image via NASA/ ESA/ JPL-Caltech/ Conroy et al.

If dark matter indeed does make up most of the halo – and all different theories on the nature of dark matter agree on that – a galaxy traveling through the halo would also leave a wake in the dark matter, not only the stars. As a NASA/JPL statement described it:

The wake observed in the new star map is thought to be the outline of this dark matter wake; the stars are like leaves on the surface of this invisible ocean, their position shifting with the dark matter.

The inner regions of the Milky Way halo have already been investigated in detail, but this is the first time astronomers have been able to similarly map the outer regions of the halo, including the wake, at a distance of 200,000 to 325,000 light-years from the center of our galaxy. (As a comparison, the visible Milky Way galaxy disk that we are more familiar with has a diameter of about 100,000 light years, so this is very far out indeed).

With the halo being so faint, how do you go about observing it? Although the stars are extremely sparse in the halo, there are still some there. The researchers measured 1,301 stars located at the vast distances of the halo, using data from the European Space Agency’s Gaia mission and NASA’s Near Earth Object Wide Field Infrared Survey Explorer (NEOWISE, which also gave name to the comet of 2020). But accurately pinpointing their distances was one of the major hurdles. So they picked only a specific kind of red giant stars, classified as K giants in the stellar classification scheme. NEOWISE could efficiently detect these stars in the infrared part of the electromagnetic spectrum, which helped the team find their precise distances in the halo and create the map.

Part of the team behind this research had predicted how the dark matter in the Milky Way halo should look like, using computer models. So when the observational data showed a wake behind the Large Magellanic Cloud and another higher density region of stars in the northern part of the halo, this was not entirely a surprise.

Team member Gurtina Besla at University of Arizona’s Steward Observatory said:

What has been a purely theoretical prediction has now been validated by observational data, providing a compelling argument for the existence of dark matter.

Lead author Charlie Conroy, professor at Harvard University, described how we can learn more about dark matter, such as what it consists of, through combining models and data:

You can imagine that the wake behind a boat will be different if the boat is sailing through water or through honey. In this case, the properties of the wake are determined by which dark matter theory we apply.

Smiling young man with glasses and beard in front of greenery.

Charlie Conroy is a professor at Harvard University and the lead researcher of the discovery of a wake in the Milky Way’s halo, created by the Large Magellanic Cloud as it orbits around the Milky Way. Image via Harvard University.

Nicolás Garavito-Camargo, a co-author of the study at University of Arizona, explained how this research applies to other galaxies as well:

The Milky Way is the only galaxy in which we can resolve the stars and the halo to this level of detail, so it is our most important ‘natural laboratory’ in which we can study how galaxies work in general. We think that what we observe here likely applies to similar galaxies throughout the universe.

The Large Magellanic Cloud is a small galaxy rotating around the Milky Way, about 160,000 light years away from us. It and its smaller companion, the Small Magellanic Cloud (often abbreviated LMC and SMC, respectively), are clearly visible with the unaided eye from the Southern Hemisphere, where they look exactly like their namesake: like curious stationary clouds. LMC is predicted to collide with the Milky Way in the distant future, and in essence, this collision has already started if you take the halo into account as a part of our galaxy.

Bottom line: Astronomers have created a map of the halo of our Milky Way galaxy – its far outer regions – showing how the Large Magellanic Cloud has created a wake along its traveled path, evidence that the satellite dwarf galaxy is only on its very first orbit around the Milky Way. The map provides a way to learn more about the nature of dark matter, thought to compose a large part of the galactic halo.

Source: All-sky dynamical response of the Galactic halo to the Large Magellanic Cloud

Via University of Arizona

Via NASA/JPL

Florida bill says companies like SpaceX retain ownership of fallen hardware

May 5th 2021 at 07:45
A hexagonal white panel is displayed, battered and worn, with the writing SpaceX faintly visible.

The parachute cover from SpaceX’s Demo-2 Crew Dragon was recovered by a fishing boat in the Gulf of Mexico, and now sits in a private memorabilia collection belonging to a SpaceX investor. According to a new bill just passed in Florida, artifacts like these belong to the spaceflight company that originally sent them to space. Image via Steve Jurvetson.

Four astronauts splashed down safely in the Gulf of Mexico on May 2, 2021, completing SpaceX’s first commercial crew long-duration mission (168 days) aboard the International Space Station (ISS). The capsule – Crew Dragon Resilience – shed parts on its way down, purposely ejecting the exterior panels to expose and deploy parachutes. These ocean-cast doors may appear discarded, but – once a new bill becomes law – such artifacts will remain the property of the “spaceflight entity,” in this case SpaceX. That’s according to the new Spaceflight Assets bill, affirmed by Florida’s legislature on April 26. The bill, which had the support of SpaceX, is now awaiting signature of Florida governor Ron DeSantis. When enacted, the law will go into effect on July 1.

A description of the bill states that it:

Provides spaceflight entity retains ownership of spaceflight asset after launch or upon reentry; requires person who finds item reasonably identifiable as spaceflight asset to report description and location to law enforcement; requires law enforcement to notify owner of spaceflight asset; authorizes owner of spaceflight asset to enter private property; prohibits person from appropriating spaceflight asset to his or her own use or refusing to surrender spaceflight asset to law enforcement or owner; provides criminal penalties.

The bill requires that anyone who finds “reasonably identifiable” spacecraft parts report them to local law enforcement and that the authorities then make a “reasonable effort” to notify the hardware’s owner. It even grants SpaceX, along with other entities involved in launching rockets and spacecraft, access to private property, if necessary, to recover discarded space-related artifacts. Anyone failing to surrender such artifacts could be charged with “misappropriation of a spaceflight asset,” a first-degree misdemeanor, punishable by up to a year in prison or a $1,000 fine. Violators may even pay additional restitution if the hardware is lost or damaged. State representative Tyler Sirois, who wrote the bill legislation, said in a statement:

The recovery of spaceflight debris is an increasingly common issue in Florida. The return of these materials is necessary to evaluate vehicle safety and performance … As Florida continues to lead the nation in commercial aerospace, our laws need to evolve with the growing and unique demands of this industry.

Florida is the first state to pass legislation protecting spacecraft debris. Previously, the recovery of spacecraft parts fell under the terms of federal laws addressing the theft of government property, including vehicles belonging to NASA or the military. That was enforced by the Outer Space Treaty, when entered into practice in 1967. Parties of the treaty – including the United States – may retain ownership of their vehicles and parts, regardless of where they are found. It applies whether the materials were found by a return to Earth, washed up on foreign shorelines, or even in outer space. And it’s been considered as successful.

According to Via CollectSpace, a website dedicated to space memorabilia and space-related artifacts:

SpaceX lobbied for the passage of the Florida Spaceflight Assets law after at least two incidents where Dragon parts were found in the possession of state residents. In January 2020, a group of fishermen off the coast of Daytona Beach came across two drogue chutes and their associated hatch from a SpaceX capsule that was used for an inflight abort test. Eight months later, a different fishing boat in the Gulf of Mexico recovered a panel from the first Crew Dragon [the historic Demo-2 mission] to return astronauts from the International Space Station in August 2020.

In at least one of those cases, a panel ended up in the private memorabilia collection belonging to a SpaceX investor.

A white, egg shaped spacecraft capsule is seen floating in the ocean water, hauled by a small boat to a larger boat nearby.

Numerous private vessels approach the Crew Dragon capsule after splashdown, as seen in this recovery photograph of SpaceX’s Demo-2 mission in August 2020. Image via Spaceflight Now/ NASA/ Bill Ingalls.

But the bill applies to more than panels and parachutes. The legislation addresses any “crewed and un-crewed capsules, launch vehicles, parachutes and other landing aids, and any ancillary equipment that was attached to the launch vehicle during launch, orbit, or reentry.” Florida residents who locate the parts must “report the description and location of the spaceflight asset to a law enforcement agency having jurisdiction over the location.”

Boosters and stages don’t necessarily need the same protection. Rockets routinely drop stages on their way to orbit. Some burn up on re-entry if high enough in the atmosphere; the rest return to Earth where they (hopefully) won’t hit people. This is why launch pads are typically built far from crowded cities and tend to launch directly over the ocean. And if the space parts make it to the ocean, most are too heavy to float and will sink, or be flat out destroyed by the impact. This is what makes space travel so very expensive, and why commercial spaceflight companies are making efforts to recover (and keep) those stages.

Bottom line: The Spaceflight Assets bill affirmed by the Florida legislature on April 26, 2021, requires that anyone who finds “reasonably identifiable” spacecraft parts make a “reasonable effort” to notify the hardware’s owner. Commercial spaceflight companies and all entities involved in spacecraft launches will retain ownership of their fallen hardware, even after the mission is over.

Read the Recovery of Spaceflight Assets bill

Via CollectSpace

The length of a day on Venus is always changing

May 5th 2021 at 07:00
Nearly full view of Venus covered in white and salmon clouds.

The thick cloud cover of Venus – which is impenetrable in visible light – has made it tough for astronomers to measure the length of the planet’s day. A new study at radio wavelengths may have some answers. Image via NASA/ JPL-Caltech.

Scientists said that they’ve finally answered the question of the length of a “day” on Venus. And the answer is … it’s always changing, by as much as 20 minutes! We knew that Venus had an exceedingly long day. A day on Venus – a single spin of the planet on its axis – is equal to approximately 243 Earth-days. What’s new is that the length of a Venus-day doesn’t stay fixed. That is, the spin of this neighboring planet regularly speeds up and slows down, by an amount measured in only minutes on earthly clocks, as the planet’s thick atmosphere interacts with its topography, or surface features.

This same study also unveiled the precise tilt of Venus’ axis and the size of its core.

The team of scientists led by Jean-Luc Margot of UCLA announced their findings in a new study published April 29, in the peer-reviewed journal Nature Astronomy. Margot explained how basic information about Venus is hidden behind its thick atmosphere:

Venus is our sister planet, and yet these fundamental properties have remained unknown.

Man with dark hair in suit and red tie.

Jean-Luc Margot lead the team that made precise measurements of Venus’ spin rate and axial tilt. Image via Jean-Luc Margot/ UCLA.

We said the day on Venus is approximately 243 Earth-days. A more precise number is 243.0226 Earth-days. That’s the same as 5832.5424 Earth-hours. If you’re someone who feels like there are never enough hours in a day, maybe Venus is for you? Just be aware that it’s hot enough on the surface of this world to melt led. Still, Venus’ day is a curiosity. In fact, the Venus-day is so long that its year is shorter, at 225 Earth-days. Its day is longer than its year! Let that rattle around in your mind a little …

As mentioned above, the inconstant timing of a day on Venus is the fault of its incredibly thick atmosphere. The atmosphere of Venus – which is largely carbon dioxide – is about 93 times as massive Earth’s, and therefore it presses down onto the planet’s surface with greater force. The surface pressure on Venus may be up to 100 times greater than on Earth. When Venus’ thick atmosphere – with its winds that can reach 224 miles (360 km) an hour – interact with solid ground, momentum is exchanged, speeding up and slowing down the planet’s rotation. Earth has the same interplay between atmosphere and ground, but its exchange only adds or subtracts a millisecond from each day.

Being able to measure a precise length of a day on Venus is important for any future exploration on the planet, because without accurate measurements on the planet’s movements, landings could be off by as much as 18.6 miles (30 km)!

In this new study, the scientists also acquired precise measurements of Venus’ axis and core. Venus is almost completely upright, with a tilt in its axis of just 2.6392 degrees. Contrast that slight tilt to Earth’s larger tilt of 23 degrees, and you’ll understand why Venus has no seasons. It takes Venus an extremely long time to complete one circuit in the tiny wobble on its axis: 29,000 years. Just as on Earth, this wobble in Venus’ axis is known as precession.

Sphere with arrow emerging at poles and red, blue, and green mottlings.

This topographic map of Venus shows the spin axis of the planet (yellow arrow), which is less than 3 degrees, meaning Venus spins nearly upright with only the smallest wobble. Image via Jean-Luc Margot/ UCLA/ NASA.

Once the scientists had the radio data on Venus’ spin, they were able to calculate the size of the planet’s core. They measure the core at 2,175 miles (3,500 km) in diameter, basically the same size as Earth’s core.

But how did the scientists come up with all these new measurements for Venus? They used radio waves, that they bounced off Venus over the course of 15 years (radar). Using the 70-meter–wide Goldstone antenna in California’s Mojave Desert, the scientists sent photons in the form of radio waves to Venus, where they penetrated the thick atmosphere, bounced off the ground, and then returned to Earth. Both the Goldstone telescope and the Green Bank Observatory in West Virginia picked up their return signals. Margot explained, likening the planet to a disco ball:

We illuminate it with an extremely powerful flashlight — about 100,000 times brighter than your typical flashlight. And if we track the reflections from the disco ball, we can infer properties about the spin.

The delay between the return signals at Goldstone and Green Bank helped the scientists estimate Venus’ spin rate, and the window of time in which the echoes from Venus are most similar revealed the planet’s tilt.

This process of bouncing photons off Venus and interpreting the return signal can be (and has been) used on other worlds in the solar system. The team want to target Jupiter’s moons Europa and Ganymede to learn some of their distant secrets as well, including more about the ocean that may hiding under a shell of ice on Europa.

Measuring a day on Venus
Credit: Jean-Luc Margot/ UCLA pic.twitter.com/dRIzEbkLXc

— Kelly Kizer Whitt (@Astronomommy) May 3, 2021

Bottom line: Scientists used radio waves to precisely measure Venus’ spin rate and the tilt of its axis. Their findings revealed a core similar in size to Earth’s and a day that regularly changes in length.

Source: Spin state and moment of inertia of Venus

Via UCLA

What Proxima’s massive flare means for our chances of alien neighbors

May 4th 2021 at 06:17
Bright circle of light on a black background.

Proxima Centauri is the closest star to the solar system and is home to a potentially habitable planet. Image via Hubble/ European Space Agency/ WikimediaCommons.

R. O. Parke Loyd, Arizona State University

Our sun isn’t the only star to produce stellar flares. On April 21, 2021, a team of astronomers published new research in the Astrophysical Journal Letters, describing the brightest flare ever measured from Proxima Centauri in ultraviolet light, which occurred on May 1, 2019. To learn about this extraordinary event – and what it might mean for any life on the planets orbiting Earth’s closest neighboring star – The Conversation spoke with Parke Loyd, an astrophysicist at Arizona State University and co-author of the paper. Excerpts from the conversation are below and have been edited for length and clarity.

Why were you looking at Proxima Centauri?

Proxima Centauri is the closest star to this solar system. A couple of years ago, a team discovered that there is a planet – called Proxima b – orbiting the star. It’s just a little bit bigger than Earth, it’s probably rocky and it is in what is called the habitable zone, or the Goldilocks zone. This means that Proxima b is about the right distance from the star so that it could have liquid water on its surface.

But this star system differs from the sun in a pretty key way. Proxima Centauri is a small star called a red dwarf – it’s around 15% of the radius of our sun, and it’s substantially cooler. So Proxima b, in order for it to be in that Goldilocks zone, actually is a lot closer to Proxima Centauri than Earth is to the sun.

You might think that a smaller star would be a tamer star, but that’s actually not the case at all – red dwarfs produce stellar flares a lot more frequently than the sun does. So Proxima b, the closest planet in another solar system with a chance for having life, is subject to space weather that is a lot more violent than the space weather in Earth’s solar system.

A photo of the surface of the sun with a towering explosion of plasma.

Solar flares – like this one captured by a NASA satellite orbiting the sun – eject huge amounts of radiation. Image via NASA/ Wikimedia Commons.

What did you find?

In 2018, my colleague Meredith MacGregor discovered flashes of light coming from Proxima Centauri that looked very different from solar flares. She was using a telescope that detects light at millimeter wavelengths to monitor Proxima Centauri and saw a big of flash of light in this wavelength. Astronomers had never seen a stellar flare in millimeter wavelengths of light.

My colleagues and I wanted to learn more about these unusual brightenings in the millimeter light coming from the star and see whether they were actually flares or some other phenomenon. We used nine telescopes on Earth, as well as a satellite observatory, to get the longest set of observations – about two days’ worth – of Proxima Centauri with the most wavelength coverage that had ever been obtained.

Immediately we discovered a really strong flare. The ultraviolet light of the star increased by over 10,000 times in just a fraction of a second. If humans could see ultraviolet light, it would be like being blinded by the flash of a camera. Proxima Centauri got bright really fast. This increase lasted for only a couple of seconds, and then there was a gradual decline.

This discovery confirmed that indeed, these weird millimeter emissions are flares.

A gray rocky planet with a pale star behind it.

Proxima b – shown here in an artist’s rendering – is rocky and might support water or even life if the atmosphere is still intact. Image via European Southern Observatory/ M. Kornmesser.

What does that mean for chances of life on the planet?

Astronomers are actively exploring this question at the moment because it can kind of go in either direction. When you hear ultraviolet radiation, you’re probably thinking about the fact that people wear sunscreen to try to protect ourselves from ultraviolet radiation here on Earth. Ultraviolet radiation can damage proteins and DNA in human cells, and this results in sunburns and can cause cancer. That would potentially be true for life on another planet as well.

On the flip side, messing with the chemistry of biological molecules can have its advantages – it could help spark life on another planet. Even though it might be a more challenging environment for life to sustain itself, it might be a better environment for life to be generated to begin with.

But the thing that astronomers and astrobiologists are most concerned about is that every time one of these huge flares occurs, it basically erodes away a bit of the atmosphere of any planets orbiting that star – including this potentially Earth-like planet. And if you don’t have an atmosphere left on your planet, then you definitely have a pretty hostile environment to life – there would be huge amounts of radiation, massive temperature fluctuations and little or no air to breathe. It’s not that life would be impossible, but having the surface of a planet basically directly exposed to space would be an environment totally different than anything on Earth.

Is there any atmosphere left on Proxima b?

That’s anybody’s guess at the moment. The fact that these flares are happening doesn’t bode well for that atmosphere being intact – especially if they’re associated with explosions of plasma like what happens on the sun. But that’s why we’re doing this work. We hope the folks who build models of planetary atmospheres can take what our team has learned about these flares and try to figure out the odds for an atmosphere being sustained on this planet.

R. O. Parke Loyd, Post-Doctoral Researcher in Astrophysics, Arizona State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: In May 2019, astronomers measured the largest flare ever from Proxima Centauri, humanity’s closest neighboring star. These flares could be bad news for life trying to develop on a planet orbiting the star.

Source: Discovery of an Extremely Short Duration Flare from Proxima Centauri Using Millimeter through Far-ultraviolet Observations

Via The Conversation

The Conversation

Space rock found on Earth traced back to origins on Vesta

April 30th 2021 at 06:04
Group of 10 people pointing at a small rock.

Shown here is the team that found the first meteorite from the breakup of asteroid 2018 LA in Botswana. They point to the space rock found there, later named Motopi Pan. Image via Meteoritics and Planetary Science/ Peter Jenniskens.

In 2018, an international team of scientists tracked a small asteroid as it streaked toward Earth and crashed into southern Africa. The team was able to find and collect pieces of the asteroid that were scattered across a Botswana game reserve. Now, the scientists believe they know the source of that asteroid. They say the space rock came from Vesta, the brightest and second-most massive object in the asteroid belt, a region of our solar system between Jupiter and Mars occupied by a great many solid, irregularly-shaped bodies of many sizes.

During the early days of the solar system, 1 to 2 billion years ago, enormous collisions nearly shattered Vesta, creating a slew of fragments that occasionally get close enough to Jupiter to hurl them in toward Earth. The researchers say it’s one of these pieces of space debris that landed in Africa in 2018.

The study of the findings was published April 23, 2021, in the peer-reviewed journal Meteoritics & Planetary Science.

Rocks from space that reach Earth’s surface are called meteorites. Most of the meteorites found on Earth were once part of asteroids from the asteroid belt that chipped off the parent body in a collision. Some rarer sources of meteorites are the moon and Mars.

When the asteroid – now known as 2018 LA – was discovered, it was only the second asteroid in space detected before hitting land. An international team guided by SETI Institute meteor astronomer Peter Jenniskens eventually found 23 fragments of the asteroid, which they estimate to originally have been 5 feet (about 1.5 meters) in diameter. The first meteorite found was named Motopi Pan after a nearby watering hole.

Grid showing 23 mostly black rocks and one pic of stars with a short white streak.

Pieces of Vesta on Earth. Asteroid 2018 LA in space (top left image by the Catalina Sky Survey) and the 1st 23 meteorites recovered on the ground as photographed in situ. Meteorites are shown in the order they were found with Motopi Pan at top left. Image via Meteoritics and Planetary Science/ Peter Jenniskens.

Jenniskens explained how they tied 2018 LA to Vesta:

Combining the observations of the small asteroid in space with information gleaned from the meteorites shows it likely came from Vesta, second largest asteroid in our solar system and target of NASA’s Dawn mission. Billions of years ago, two giant impacts on Vesta created a family of larger, more dangerous asteroids. The newly recovered meteorites gave us a clue on when those impacts might have happened.

NASA’s Dawn mission, which visited the asteroid belt and studied Vesta in 2011, found that the asteroid’s surface is covered in coarse-grained basaltic and silicate-rich rocks. The rocks are types known as howardite, eucrite and diogenite (HED). Other meteorites that scientists have recovered and studied on Earth with this same makeup are known as HED meteorites. Analysis of Motopi Pan conducted at University of Helsinki, Finland, showed it to also be an HED meteorite. Tomas Kohout of the University of Helsinki said:

We managed to measure metal content as well as secure a reflectance spectrum and X-ray elemental analysis from a thinly crusted part of the exposed meteorite interior. All the measurements added well together and pointed to values typical for HED type meteorites.

The scientists eventually studied more of the 23 space rocks that they found, although they did find some variability between the meteorites. Roger Gibson of Witts University in Johannesburg, South Africa, said:

We studied the petrography and mineral chemistry of five of these meteorites and confirmed that they belong to the HED group. Overall, we classified the material that asteroid 2018 LA contained as being howardite, but some individual fragments had more affinity to diogenites and eucrites.

When Dawn explored Vesta, it imaged the Antonia impact crater that was created in a collision 22 million years ago. One-third of all HED meteorites found on Earth were ejected 22 million years ago. The scientists wanted to know if Motopi Pan was also ejected from Vesta in the collision that created the Antonia crater at that time. Kees Welten of University of California, Berkeley, said:

Noble gas isotopes measurements at ETH in Zürich, Switzerland, and radioactive isotopes measured at Purdue University showed that this meteorite too had been in space as a small object for about 23 million years, but give or take 4 million years, so it could be from the same source crater on Vesta.

The researchers examined lead isotopes in zircon minerals to find that Motopi Pan experienced melting events 4.563 billion years ago and again 4.234 billion years ago. These two big impact events on Vesta billions of years ago helped to create the material of asteroid 2018 LA that was subsequently launched from the surface of Vesta in another impact some 22 million years ago. The billion-year-old impacts coincide with information already known about Vesta: Vesta experienced two significant impact events that created the Rheasilvia impact basin and the underlying and older Veneneia impact basin. Jenniskens elaborated:

We now suspect that Motopi Pan was heated by the Veneneia impact, while the subsequent Rheasilvia impact scattered this material around. If so, that would date the Veneneia impact to about 4234 million years ago.

Another possible origin for Motopi Pan on Vesta is a different crater from Antonia. This crater is named Rubria and is associated with the Rheasilvia impact. Jenniskens said:

On top of Rheasilvia impact ejecta is the 6.5-mile (10.3-km) diameter Rubria impact crater, slightly smaller than the 10.3-mile (16.7-km) Antonia crater, and slightly younger at 19 +/- 3 million years, but a good candidate for the origin crater of Motopi Pan.

Incredibly detailed patches of color and lines on a large oval.

View larger. | This high-resolution geological map of Vesta comes from Dawn spacecraft data. Brown colors represent the oldest, most heavily cratered surface. Purple colors in the north and light blue represent terrains modified by the Veneneia and Rheasilvia impacts, respectively. Light purples and dark blue colors below the equator represent the interior of the Rheasilvia and Veneneia basins. Image via NASA.

While the exact crater for the source of 2018 LA is yet to be determined, it appears that Earth has received space rocks that once were a part of Vesta.

Bottom line: In 2018, an asteroid smashed into Earth over Botswana. Pieces were discovered in the Central Kalahari Game Reserve, and now researchers have revealed that the analysis shows them to have come from Vesta.

Source: The impact and recovery of asteroid 2018 LA

Via SETI Institute

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