The molecule hydroxyl (HO) is common on Earth, but astronomers have not yet determined how abundant it is on other worlds. For the first time, astronomers have conclusively detected it in the atmosphere of an ultra-hot Jupiter, WASP-33b.
WASP-33b is a strange exoplanet. 400 lightyears away from us, the planet is known as an ultra-hot Jupiter: it’s a gas giant that orbits its host star closer than Mercury does to our own Sun. That extreme distance makes the atmosphere of WASP-33b reach a temperature of over 2,500° C, hot enough to melt most metals.
That exoplanet is a great candidate for studying alien atmospheres, because it’s so hot. At those temperatures, chemicals in the atmosphere emit radiation with distinct spectral fingerprints. As WASP-33b orbits around its star, the radiation emitted by the chemicals periodically redshifts and blueshifts, allowing astronomers to pick them out against the glare of the parent star.
They found hydroxyl – a molecule of one oxygen atom and one hydrogen atom (abbreviated as OH). Hydroxyl likely plays an important role in the chemical mixture of WASP-33b’s atmosphere as it interacts with water vapor and carbon monoxide.
The lead researcher based at Queen’s University Belfast, Dr. Stevanus Nugroho, said, “This is the first direct evidence of OH in the atmosphere of a planet beyond the Solar System. It shows not only that astronomers can detect this molecule in exoplanet atmospheres, but also that they can begin to understand the detailed chemistry of this planetary population.”
On Earth, hydroxyl is formed in the atmosphere when water vapor interacts with oxygen. On WASP-33b, the hydroxyl likely forms when the intense heat from the star blasts apart water vapor.
“We see only a tentative and weak signal from water vapor in our data, which would support the idea that water is being destroyed to form hydroxyl in this extreme environment,” explained Dr. Ernst de Mooij from Queen’s University Belfast, a co-author on this study.
As to the importance of the work, Dr. Neale Gibson, Assistant Professor at Trinity College Dublin and co-author of this work, said, “The science of extrasolar planets is relatively new, and a key goal of modern astronomy is to explore these planets’ atmospheres in detail and eventually to search for ‘Earth-like’ exoplanets – planets like our own. Every new atmospheric species discovered further improves our understanding of exoplanets and the techniques required to study their atmospheres, and takes us closer to this goal.”
Being able to look up at a clear, dark sky is becoming more and more rare in the rich world. Authors, artists, and even scientists have started to express concern about what our lack of daily exposure to a dark night time sky might mean for our psyche and our sense of place in the universe. Now a team has collected photometric data at 44 sites around the world in an attempt to quantify how dark the night sky actually is at different places on the globe. So where was the darkest place surveyed? The Canary Islands.
It just so happens that the lead researcher on the project, Dr. Miguel Alarcón is from that set of islands off the west coast of Africa. The paper he and his colleagues wrote, soon to be published in The Astronomical Journal, used a series of photometers, confusing called TESS (not to be confused with the Transiting Exoplanet Survey Satellite) to try to get a baseline of how dark the night sky is throughout the world.
The team collected 11 million points of data from places as far apart as Namibia, Australia, and the US. While this did not include some more popular astronomy spots, such as the highlands of Antarctica, it was a good sample of different conditions. As mentioned above, the Canary Islands had the lowest levels of background light of anywhere studied. Only about 2% of the light in the sky at night comes from artificial light at the Roque de los Muchachos Observatory in Garafia.
However, there are other, natural sources of light pollution that affect different geographies differently. The moon and the milky way are standard features of the night sky and certainly contribute to the natural brightness of it. However, there are other, more variable sources that this study monitored. These include a glow in the upper atmosphere that is caused by a combination of factors, such as the solar cycle, geographical location, and the time of year.
Another source is known as the “gegenschein” or the anti-solar point, directly opposite from the sun in the night sky. This can only be seen in extremely dark places, and the astronomy institute on the Canary Islands (IAC) is one of them.
Just because it has some of the darkest skies does not mean it’s the best place for all observations though. Other factors, such as atmospheric seeing and temperature fluctuations can cause problems with observations. The real take away from this research is that if you truly want to see the night sky as our ancestors did, it might be worth a trip to some islands off the coast of Africa.
Lead Image: Image of the Roque de los Muchachos Observatory on the Canary Islands (upper part) and the La Silla Observatory in Chile in the lower part. The composition makes the Milky Way appear circular. Credit: Juan Carlos Casado & Petr Horálek
Main sequence stars fuse hydrogen in their cores. It’s how they produce the energy they need to shine and keeps them from collapsing under their own weight. As hydrogen is fused into helium, there is less hydrogen available in the core. This can pose a challenge for large stars. They need to fuse a tremendous amount of hydrogen to keep shining, and they can’t do that when core hydrogen is depleted. Fortunately, they can solve this problem by mixing more hydrogen into their core. A new study in Nature Astronomy shows us how this mixing happens.
With stars like the Sun, the core is surrounded by a radiative layer. This layer is so dense that it takes photons tens of thousands of years to move through it. The atoms in this layer don’t churn much, so there isn’t much mixing. Above the radiative layer is a convective layer, which does mix. Hydrogen within the Sun’s core isn’t replenished as it’s fused into helium, but there is still plenty of core hydrogen to power the Sun for billions of years.
If larger stars had a similar internal structure as our Sun, they would burn through core hydrogen fairly quickly, filling the core with “helium ash” that would limit the star’s ability to fuse hydrogen. So astronomers have thought that large stars have a convective core, which would allow hydrogen from higher layers to be mixed into the core. But how do you prove that?
This new study used a method known as asteroseismology, which looks at how the surface of a star moves and changes in brightness. While some of this can be caused by things like stellar flares, much of it is caused by sound waves within the star. The process is similar to the way you might study the vibrations of a bell by listening to its ring. Since a star’s internal vibrations are affected by the density and motion of its interior, asteroseismology is a powerful way to study stars.
The team looked at 26 B-type stars that are known to pulse in brightness. These bright blue stars are between 3 and 20 times the mass of our Sun, and they pulse at a rate from 12 hours to 5 days. Using data from NASA’s Kepler mission, the team was able to show that many of these stars have a convective core, thus allowing hydrogen to mix.
One interesting result was that the amount of mixing doesn’t correlate with the age of the star. It is not the case that mixing increases as a star ages and gets hotter. Instead, the rate of mixing is quite variable. Some stars have very little core mixing, while others mix at a rate a million times higher. Rather than age, the mixing seems to be related to the amount of internal rotation a star has.
There is plenty more to study here. The level of mixing in a star’s core can affect the lifetime and evolution of the star. While large stars typically have much shorter lifetimes than our Sun, their lifetimes may not simply depend on their mass. As we apply asteroseismology to more stars in the future, we will likely find more factors that are in the mix.
Older stars should slow down, but new observations reveal that they have just as much of a spring in their step as their younger cousins. Astronomers suspect that complex interactions with the star’s magnetic field might be to blame.
All stars spin. And all stars have magnetic fields. As they age, they should slowly spin down through a process called magnetic breaking. Occasionally the magnetic field of a star can fling material away (like in the case of a coronal mass ejection), which saps angular momentum from the star and slows it down.
To test this idea, astronomers had been using observations of starspots to monitor the spin rate of distant stars. Those results had already suggested that stars may be spinning faster than expected, but the technique had been limited to younger stars, as older stars feature fewer spots.
Asteroseismology studies variations in a star’s output as a way to measure the sound waves crashing around inside of it. When stars spin, the frequencies of vibration can split into different frequencies. The main advantage of this technique is that it can be used on stars of any age.
The team found that older stars were spinning much faster than models of magnetic breaking have predicted. This implies that the situation is much more complex than we had assumed.
Lead author on the paper, Dr Oliver Hall, said, “Although we’ve suspected for some time that older stars rotate faster than magnetic braking theories predict, these new asteroseismic data are the most convincing yet to demonstrate that this ‘weakened magnetic braking’ is actually the case. Models based on young stars suggest that the change in a star’s spin is consistent throughout their lifetime, which is different to what we see in these new data.”
Astronomers will need to develop more sophisticated models to account for the new observations. As to the future of our own sun, co-author Dr Guy Davies said, “These new findings demonstrate that we still have a lot to learn about the future of our own Sun as well as other stars. This work helps place in perspective whether or not we can expect reduced solar activity and harmful space weather in the future. To answer these questions we need better models of solar rotation, and this work takes an important step towards improving the models and supplying the data needed to test them.“
A new report from the US Government Accountability Office (GAO) says that the launch of the long-awaited, highly anticipated James Webb Space Telescope (JWST) will very likely be delayed due to an anomaly identified in the Ariane 5 launch vehicle. Launch for JWST is currently scheduled for October 31, 2021, but that date could slip by at least a couple of weeks.
As we reported yesterday, the usually reliable Ariane 5 has experienced problems on two previous launches where unexpected vehicle accelerations occurred when the fairing separated from the rocket. The fairing is the nose cone used to protect a spacecraft payload during launch and acceleration through Earth’s atmosphere.
The Ariane 5 has been grounded for several months while the European Space Agency and Arianespace investigate the issue. In both anomalies, the payloads were successfully placed in orbit, however. There are two Ariane launches on the manifest before the JWST launch, and those launches are now expected no earlier than June and August 2021, respectively.
During a media briefing on May 11, Greg Robinson, Program Director for JWST at NASA’s Science Mission Directorate said that ESA and Arianespace are going through the process of getting the rocket ready for the upcoming first launch, and once the first launch takes place, “we’ll be able to launch in about four months after that.”
The two Ariane 5 launches are scheduled to carry the Eutelsat Quantum satellite and Star One D2 satellite.
The GAO report, released on May 13, 2021, said that Arianespace must demonstrate that the issue has been corrected on at least one of those launches before JWST will be allowed to launch. As of now, “the JWST launch had not been rescheduled; however, project officials assessed the risk that the JWST launch date could be rescheduled as highly likely. The project has received briefings on the investigation’s progress from its international partners and is continuing to monitor the situation.”
NASA officials at the media briefing this week admitted that the margin in their schedule in preparing and shipping JWST to South America is basically zero.
“When we ship, the schedule margin will be pretty close to zero, but still on plan,” Robinson said, “Right now, we are not working any liens, and we’re in a really good place.”
The GAO report indicated the JWST project has used schedule reserves—extra time set aside to accommodate unforeseen risks or delays—faster than expected to address issues such as repairing and strengthening the sunshield.
“As a result, the project has less schedule reserve than planned to complete remaining activities,” the report said. “The project is also completing redesigns for key parts of the observatory, including actuators, which help unfurl the sunshield. Further, the project continues to address technical problems that could affect the project’s ability to meet cost commitments if the contractor workforce is needed longer than planned.”
Including the launch delay risk, the report said JWST project managers are working on managing 39 risks. Of the 39 risks, NASA will continue to manage 26 after launch, including those related to sunshield deployment and the functionality of the observatory’s sensitive, near-infrared camera.
Alarmingly, some of these risks could result in loss of mission, but NASA has assessed that they are unlikely to occur.
“Since the project’s schedule and costs were baselined in 2009,” the GAO report says, “the launch date has been delayed by over 7 years and costs have increased by 95 percent. Due to early technical and management challenges, contractor performance issues, and low levels of cost reserve, the JWST program experienced schedule overruns, launch delays, and cost growth.”
But recently, the project has completed significant technical milestones, such as successfully completing the final set of acoustics and vibration testing in October 2020, and performing sunshield deployment exercises in December 2020.
In a mission that has seen significant postponements, it seems an iconic irony that now as JWST seems finally ready to launch, it might experience another unexpected delay.
If you’re a fan of titanium, you should head to the nearest supernova. You’ll get more than enough of it. And its presence can help astronomers understand how supernovae work.
We understand the basic picture of how the most massive stars die. Once an iron core fuses in their centers, they stop producing energy from nuclear reactions. The star collapses, squeezing the iron core to such a degree that it turns into a proto-neutron star. The rest of the star bounces off of that neutron core and begins to explode. Either the core remains, or itself collapses into a black hole.
But that’s not the end of the story. Simulations of these supernova explosions show that the blast wave quickly loses energy and stalls before the star goes boom. Astrophysicists believe that a flood of neutrinos – tiny, nearly-massless particles released when the iron core converts to a neutron star – reinvigorates the shock wave and really gets the whole supernova party going.
As compelling as this story seems in our computer simulations, it’s tough to actually observe, since we can’t peek inside of a supernova as it’s going off. So we have to take the next best thing and try to predict how these explosions would behave and what they might produce, and compare that to our best guesses from simulation.
And who knew that titanium would hold the key.
Most, if not all, of the titanium you encounter in your everyday life was forged inside of a dying star. It can only form in the intense, neutrino-driven fury of the supernova blast, but to date astronomers have not seen titanium in the ejecta of supernova.
Now, a team of astronomers used NASA’s Chandra X-ray Observatory to study Cassiopeia A (Cas A), the remnants of a supernova that went off 350 years ago sitting 11,000 light-years away.
“Scientists think most of the titanium that is used in our daily lives — such as in electronics or jewelry — is produced in a massive star’s explosion,” said Toshiki Sato of Rikkyo University in Japan, who led the study that appears in the journal Nature. “However, until now scientists have never been able to capture the moment just after stable titanium is made.”
“We have never seen this signature of titanium bubbles in a supernova remnant before, a result that was only possible with Chandra’s incredibly sharp images,” said co-author Keiichi Maeda of Kyoto University in Japan. “Our result is an important step in solving the problem of how these stars explode as supernovae.”
“When the supernova happened, titanium fragments were produced deep inside the massive star. The fragments penetrated the surface of the massive star, forming the rim of the supernova remnant, Cas A,” said co-author Shigehiro Nagataki of the RIKEN Cluster for Pioneering Research in Japan.
The presence of titanium is a smoking gun that neutrinos were responsible for producing the supernova blast, and the observations will help validate current models and lead to a more detailed understanding of these powerful explosions.
The primary mirror of the long-awaited James Webb Space Telescope (JWST) was opened for the last time on Earth before the launch of the observatory, currently scheduled for October 31, 2021.
During some of the final checkouts before the telescope heads to space, engineers commanded the 18 hexagonal mirrors to fully expand and lock into place, just like they will do once the Webb telescope reaches its destination in space.
“Over the past few months, we have completed almost all of our deployments associated with post environmental testing,” said Bill Ochs, Project Manager for JWST at NASA, during a media briefing this week. “This includes things like mirror, the solar array, and as well as the very complex and challenging final successfully deployment of the sunshield, which is now folded back up and undergoing final stowing now.”
Ochs said the engineering and science teams have also completed the final ground segment tests where they actually commanded the observatory from the telescope’s Mission Operations Center at the Space Telescope Science Institute in Baltimore, Maryland.
To deploy, operate and bring the golden mirrors into focus requires 132 individual actuators and motors in addition to complex backend software to support it. A proper deployment in space is critically important to allow the individual mirrors to work as one functional and massive reflector
The deployment on Earth, however, involves supporting the mirrored panels from a crane in a way that simulates the zero-gravity environment in space.
“We effectively have that mirror float like it does in space,” explained Northrop Grumman program manager Scott Willoughby. “We designed the mirror wings to operate in space, but we have to test them on the ground – and gravity can be pretty humbling.”
Once the wings are fully extended and in place, extremely precise actuators on the backside of the mirrors position and bend or flex each mirror into a specific “prescription.” Testing of each actuator and their expected movements was completed in a final functional test earlier this year.
“We are getting very close to shipping and launch,” said Greg Robinson, Program Director for JWST at NASA’s Science Mission Directorate. “Over the past year — this year of a pandemic — our employees have learned to live and work together like we’ve never imagined. But we kept everything moving … and now we are just doing all those ‘lasts’ — the last tests, last deployments we’ll ever do on Earth, the last stow.”
The plan is that JWST will be placed inside a large climate-controlled shipping container and taken on a ship from the Northrup Grumman facility where it is now, in California, to the European rocket facility at Kourou in French Guiana. The trip will take approximately two weeks and involve passage through the Panama Canal.
JWST will be launched aboard an Ariane 5 rocket. However, the usually reliable Ariane 5 has seen problems on two previous launches with a “less than fully nominal separation of the fairing.” The rocket has been grounded for months to sort it out, and with two other launches on the manifest before JWST, this issue could potentially delay the launch of the high-profile space telescope in October, but perhaps only for a couple of weeks.
“They’re going through the process of getting the rocket ready for the upcoming launch, the first of the three,” Robinson said. “Once they launch, we’ll be able to launch in about four months after that.”
However, Robinson said on NASA’s and Northrup Grumman’s end, everything is going well, and they are not working any problems.
“Right now, we are not working any liens,” he said. “We are getting close to the goal line and just need to punch it over. We are in a really good place but have several reviews ahead of us to get to the next steps.”
What if we had the ability to chase down interstellar objects passing through our Solar System, like Oumuamua or Comet Borisov? Such a spacecraft would need to be ready to go at a moment’s notice, with the capacity to increase speed and change direction quickly.
“Bringing back samples from these objects could fundamentally change our view of the universe and our place in it,” says Christopher Morrison, an engineer from the Ultra Safe Nuclear Corporation-Tech (USNC-Tech) who submitted the proposal to NIAC.
The concept Morrison and his team propose is a radioisotope-electric-propulsion spacecraft that relies on Chargeable Atomic Battery (CAB) technology, a power system that USNC has been developing for commercial use. The batteries are compact and possess one million times the energy density of state-of-the-art chemical batteries — as well as fossil fuels.
“Radioisotopes have about the same amount of total energy stored in each atom,” Morrison explained. “How quickly they release that energy depends on the half-life. Pu-238 has a half-life of 88 years, great for long missions to the outer solar system. The CAB batteries we are developing at USNC-Tech have shorter half-lives and possess a higher power density. In the NIAC, we are using a radioisotope with a five-year half-life and a power density over 30 times that of Plutonium-238 (Pu-238).”
Pu-238 is NASA’s usual nuclear power of choice for its spacecraft. It has been used for more than two-dozen U.S. very successful space missions — such as New Horizons, and the Curiosity and Perseverance Mars rovers – for their radioisotope power systems (RPS).
Pu-238, however faces some challenges. Only a limited amount of Pu-238 can be produced (a mere 14 ounces (400 grams) each year right now with a path toward 50 ounces (1500 g) over the next few years). This is just barely enough to meet NASA’s future mission needs for its major programs.
Smaller programs and commercial companies face challenges not only because of the supply crunch, but also because Pu-238 is considered a special nuclear material with nonproliferation concerns. The radioisotopes in the CAB technology are instead commercial in nature, in fact many of them are heavily used in the medical industry for cancer treatment therapies.
“CAB batteries combined with electric propulsion would be very simple systems,” Morrison told Universe Today. “This is all proven technology. The real innovation we are taking advantage of is the current regulatory environment. Before 2019, there was not a legal framework for commercial companies to use nuclear-based power. Now its officially sanctioned.”
Presidential memo NPSN-20 in 2019 directed the Department of Transportation, and specifically the Federal Aviation Administration, to develop a tiered regulatory system that would allow commercial companies to launch nuclear-powered spacecraft.
Morrison’s proposal explains that the “CAB is easier and cheaper to manufacture than Pu-238 and the safety case is greatly enhanced by the CAB’s encapsulation of radioactive materials within a robust carbide matrix. This technology is superior to fission systems for this application because fission systems need a critical mass whereas radioisotope systems can be much smaller and fit on smaller launch systems, reducing cost and complexity.”
The CAB powered spacecraft, dubbed the “Extrasolar Express,” has a fueled mass of just under one ton. SpaceX’s Falcon 9, in contrast, can place over 20 tons into orbit. What would be done with all the extra room in the launch vehicle?
Morrison explains: “We can trade some of that mass for an extra speed boost away from Earth. In addition, some of the extra mass can be used to increase safety by including a large robust shield that protects the radioisotope and ensures no release even the worst-case launch accident. Once in a high orbit the shield can be ejected, and the spacecraft can travel unhindered on its mission.”
Extrasolar Objects Now on the Scene
Before the two unusual and intriguing interstellar objects burst on the scene in our solar system (Oumuamua in 2017 and Borisov in 2019) astronomers hadn’t widely considered that wandering interlopers from other star systems might routinely pass by. Now, scientists calculate that an average of seven such objects pass inside Earth’s orbit each year. Finding out more about these objects is an enticing prospect, since right now, all we can do is watch them with telescopes as they speed past us.
“These objects seem to come fairly close to us,” Morrison said, “creating a mission to catch up to one is not a question of distance but a question of speed. That changes the equation as opposed to most missions, which need longevity. This is just a velocity problem, because you can intercept it and grab a sample and head back to Earth as long as you have the delta v to accomplish the mission.”
Morrison explained the potential mission plan for the Extrasolar Object Interceptor and Sample Return : Launch the Interceptor spacecraft towards Jupiter and wait for a suitable extrasolar object to be detected.
“You might have to wait a year or so,” he said, “but no matter what, you’ll likely have to execute a plane change, because these objects don’t come in on our ecliptic plane. The idea is to fly towards Jupiter, hopefully be in a good place to do a slingshot around Jupiter to get into the same plane orientation as the object.”
The spacecraft could be similar in size and mass to the Dawn mission, which also used electric propulsion. But instead of Dawn’s enormous solar panels, the CAB would provide enough power to create a speedy spacecraft. The Interceptor would need large heat rejection radiators, which (like Dawn’s solar panels) would be the largest part of the spacecraft.
“I consider myself more of the ‘Scotty’ of designing this Interceptor mission, but I’d get a Spock to help figure out the science part,” Morrison mused.
CABs are manufactured using non-radioactive materials and then “charged” in a radiation field to create a specific radioisotope. Morrison said there are a lot of different radioisotopes of interest (for example Cobalt-60 and Thulium-170) and the technology can be catered to meet the power density and lifetime needs of a customer. Many of the CAB technology potential customers are terrestrial companies looking at underwater or underground applications.
“The technology is being pioneered for watt-scale lunar heating applications in the near-term, but the NIAC proposal represents the sportier version of the technology.”
The NIAC Program bills itself as nurturing visionary ideas that could transform future NASA missions with the creation of breakthroughs, while engaging innovators and entrepreneurs as partners. Even if the Extrasolar Object Interceptor and Sample Return never makes it as a “real” mission, Morrison and USNC will continue to work towards making their CAB a viable power source for both Earth and space.
“I’m extremely grateful we received NIAC funding,” Morrison said, “our company is already investing our own money into this technology. We’d like the CAB to be the Duracell battery of the future for anything that seems impossible – like long duration space missions, or in remote environments on Earth.”
Beyond CAB batteries, the USNC company has been developing other nuclear technologies. “Radioisotopes used in CABs are hot rocks that produce consistent heat over a long period of time. A fission reactor is a different type of nuclear technology that can be turned on and off, up and down” explains Chris. USNC is developing a small modular fission reactor for use in the Canadian Arctic and this project is the main focus of the company’s efforts.
“Canada spends many hundreds of millions a year on diesel for generators to power their small towns in remote regions ,” Morrison said, “and they really want to change to using small modular reactors.”
It turns out that power systems that work well for remote locations on Earth are good for remote locations in space, too. UNSC-Tech, where Morrison works, is a subsidiary of USNC focused on the aerospace industry and advanced terrestrial systems. USNC-Tech is developing fission propulsion technology with NASA and DARPA as well as a Lunar and Martian reactor dubbed the “Pylon reactor.”
“USNC-Tech is designing the ‘LEGO’ bricks for space nuclear technology. Space missions would use the same fundamental terrestrial technology arranged in a different configuration to accomplish brave new things in new places,” Morrison explained. “The Extra Solar Express NIAC though is probably my favorite one.”
Lead image caption: Artist’s depiction of the Extrasolar Object Interceptor. Credit: Christopher Morrison
Astronomers finally managed to observe a comet nearing the end of its life. And they found that it’s covered in talcum powder. They have no idea why.
It’s usually very tough to observe the nucleus of a comet. When comets come close enough to observe, they become active. Any volatile ices, like water and ammonia, evaporate under the intense heat of the sun, giving them their characteristic coma. While a pretty sight for stargazers, the coma obscures the nucleus.
When comets are far from the sun and inactive, they’re pretty much too far away to observe.
But in 2016 astronomers got lucky with Comet P/2016 BA14 (PANSTARRS). When it was first discovered, it was mistaken for an asteroid, but follow-up observations revealed that it was actually the burnt-out husk of a comet. After so many trips too close to the sun, it had simply lost almost all of its ices.
In March of 2016, a team of astronomers from the National Astronomical Observatory of Japan (NAOJ) and Koyama Astronomical Observatory of Kyoto Sangyo University used the Subaru telescope to monitor the comet as it approached within 3.6 million kilometers of Earth – a rare opportunity to get a (relatively) closeup view of such a strange comet near the end of its life.
They found that the surface of P/2016 BA14 is covered with organic molecules and large grains of phyllosilicate.
On Earth, you may be more familiar with large grains of phyllosilicate as talcum powder.
Analysis of the talcum found that the comet had once been heated to over 330 degrees Celsius, which is far hotter than its current orbit allows. This suggests that at one time the comet managed to pass much closer to the sun.
However, the team isn’t sure if the talcum was there all along – and just exposed once the comet lost its coma – or it formed later on.
“This result provides us a precious clue to study the evolution of comets.” comments Dr. Takafumi Ootsubo, the lead author of this research, “We believe that further observations of the comet nuclei will enable us to learn more about the evolution of comets.”
The Gaia spacecraft is an impressive feat of engineering. Its primary mission is to map the position and motion of more than a billion stars in our galaxy, creating the most comprehensive map of the Milky Way thus far. Gaia collects such a large amount of precision data that it can make discoveries well beyond its main mission. For example, by looking at the spectra of stars, astronomers can measure the mass of individual stars to within 25% accuracy. From the motion of stars, astronomers can measure the distribution of dark matter in the Milky Way. Gaia can also discover exoplanets when they pass in front of a star. But one of the more surprising uses is that Gaia could help us detect cosmic gravitational waves.
A new study shows how this can be done. The work is based on an earlier study done using Very Long Baseline Interferometry (VLBI) where radio telescopes measured the position and apparent motion of quasars. Quasars are bright radio sources billions of light-years away. Because quasars are so far away, they act like fixed points in the sky. By precisely measuring quasars, we can pinpoint positions on Earth so accurately that we can see how continents drift due to plate tectonics, and how the rotation of Earth slows down over time.
While the quasars are essentially fixed points, their light can be deflected slightly through gravitational lensing. If a star passes into a quasars line of sight, the quasar would appear to shift slightly. Since gravitational waves can also deflect light, we could detect the presence of gravitational waves through the apparent wobble of quasars. The VLBI observations of quasars have found no indication of gravitational waves, placing an upper limit on them in our region of space.
Although the position measurements of Gaia aren’t as accurate as VLBI, they are accurate enough to detect gravitational lensing. In fact, astronomers have to account for the lensing effect of the Sun when analyzing Gaia data. So the team looked at Gaia’s position data for 400,000 quasars. Although quasars aren’t stars, many of them are optically bright, and Gaia measures their position just as if they were stars. The team looked for statistical evidence of wobble in the Gaia quasar data and found none. But given the large number of quasars observed, they could place a stronger upper bound on local gravitational waves. From this study, the team showed that there are no binary supermassive black holes within our local group, which includes both the Milky Way and the Andromeda galaxy.
What’s great about this study is that it shows the power of big data. When we observe the heavens with both great scale and great precision, astronomers can use the data in innovative ways. Gaia was never intended to study gravitational waves, and yet it can all the same. As we continue to move into the realm of big data astronomy, who knows what more we will discover.
Within the Milky Way, there are an estimated 200 to 400 billion stars, all of which orbit around the center of our galaxy in a coordinated cosmic dance. As they orbit, stars in the galactic disk (where our Sun is located) periodically shuffle about and get closer to one another. At times, this can have a drastic effect on the star that experience a close encounter, disrupting their systems and causing planets to be ejected.
Knowing when stars will make a close encounter with our Solar System, and how it might shake-up objects within it, is therefore a concern to astronomers. Using data collected by the Gaia Observatory, two researchers with the Russian Academy of Sciences (RAS) determined that a handful of stars will be making close passes by our Solar System in the future, one of which will stray pretty close!
The study was conducted by Vadim V. Bobylev and Anisa T. Bajkova, two researchers from the Pulkovo Observatory’s Laboratory of Galaxy Dynamics in St. Petersburg, Russia. As they indicated, they relied on astrometric data from the Gaia mission’s Early Data Release 3 (EDR3), which revealed kinematic characteristics of stars that are expected to pass within 3.26 light-years (1 Parsec) with the Solar System in the future.
To start things off simple: our Solar System is composed of eight designated planets and several minor (aka. dwarf) planets orbiting our main sequence G-type yellow dwarf Sun, which is surrounded by an outer ring of icy objects known as the Kuiper Belt. Beyond this, at a distance of roughly 1.63 light-years from the Sun (0.5 parsecs), is a massive cloud of icy debris known as the Oort Cloud, which is where long-period comets originate.
These comets are generally the result of objects making close flybys with the Solar System and knocking objects loose, to the point that they periodically fly through the Solar System and around the Sun before heading back out. The outer edge of the Oort Cloud is estimated to be 0.5 parsecs (1.6 light-years) from our Sun, which makes them particularly responsive to perturbations from a number of sources. As Dr. Bobylev told Universe Today via email:
“These perturbations include, first of all, the effect of the gravitational attraction of the Galaxy – the so-called galactic tide, secondly, the effect from giant molecular clouds – when the solar system flies at a sufficiently close distance to them, and thirdly – the effect from approaching single stars fields.
“The approach of the solar system with single stars in the field is a very rare event. Moreover, the impact depends (according to Newton’s law of attraction) both on the mass of the passing star and on the distance to which the approach takes place.”
For astronomers, the process of searching for stars that may have flown by our Solar System in the past (and which may pass us by in the future) began in the 1960s. The research has improved as more sophisticated instruments have become available, leading to more detailed catalogs on nearby celestial objects. In order to know which stars will make a close encounter, said Bobylev, you need to know their distance and their three velocities.
The consists of the two properties of proper motion – right ascension, declination – and radial velocity. Once you have all that, you can conduct astrometry, which is the precise measurement of the positions and movements of stars and other celestial bodies. It was for this very purpose that the ESA’s Hipparcos satellite (1989-1993) and Gaia Observatory (2013-present) were created.
Thanks to the precise data they have provided, and the updated catalogs on millions of stars and other celestial objects, astronomers are able to determine which of them are likely to make a close encounter in the future. For the sake of their study, Bobylev and Bajkova relied on the following three methods:
“The methods consist in constructing galactic orbits of the studied stars and the Sun. Then, for each star, two main parameters of approach are determined – the minimum distance between the orbit of the solar system and the star and the moment of approach. Integration occurs on the +/-5 Myr interval.
“Therefore, in our work, we used, firstly, the simplest linear method, secondly, the integration of motion in the axisymmetric potential of the Galaxy, and thirdly, in the nonaxisymmetric potential of the Galaxy, where the influence of the spiral structure on the motion of objects was taken into account.”
In the end, all three methods yielded similar results: one star, designated 4270814637616488064 in the Gaia EDR3 database, would be making a particularly close encounter a little over a million years from now. Better known as Gliese 710 (HIP 89825), this variable K-type orange dwarf star is about 60% as massive as our Sun and located some 62 light-years from Earth in the Serpens constellation.
“What is remarkable about it is that it is a candidate for a very close approach to the solar system in the future,” said Bobylev. “This candidate was first identified by Garcia-Sanchez et al., Astron. J. 117, 1042 (1999) in the analysis of stars from the Hipparcos catalog (1997).”
Specifically, the simulations Bobylev and Bajkova conducted showed that Gliese 710 would be making its close flyby 1.32 million years from now and would pass within 0.02 parsecs (just shy of 24 light days) of our Sun. As for what this could entail for our Solar System (and anything living here by then), Bobylev explained that considerable research has already been done on that, and the indications were not so frightening:
“A very interesting simulation of the close flight of the star Gliese 710 past the solar system was carried out by Berski, F. and Dybczynski, P., A&A, v. 595, L10, 2016. They showed that after the approach, a cometary shower will occur from the outer boundaries of the Oort Cloud towards the inner region of the Solar System. True, the flux is small – about a dozen comets a year, and it will appear with a delay of 1 million years after the flight of the star.”
So, assuming human beings (or their genetic progeny) are still living in the Solar System 2.32 million years from now, they will be treated to some added comet activity. This could pose some hazards, depending on the trajectories of these comets and the extent of human infrastructure in space. Or it could just mean more opportunities for backyard astronomy, or whatever the futuristic equivalent is!
In any case, it’s always good to know when shakeups will happen and how serious they will be. Such is the significance of this research, in that it eliminates much of the uncertainty surrounding stellar close encounters and the effect they can have. Said Bobylev:
The main significance of our work is that we know with certainty that, both in the past, and in the future, there may be close encounters of stars with the solar system. There can be all sorts of surprises in the form of the appearance of comets and asteroids near the Earth.
Our Solar System has experienced more than a few in the past, and these played a significant role in its evolution. It’s entirely possible that life as we know it owes its existence to close encounters, so best to keep track of any future events!
Two neutron stars. One is 50% more massive than the other, yet they are almost exactly the same size. The results have big implications for understanding what neutron stars are really made of.
In 2019 a team of astronomers led by Thomas Riley, a postdoctoral researcher, and Anna Watts, a professor of astrophysics at the University of Amsterdam, measured the mass and radius of a certain neutron star. The neutron star in question was J0030+0451 (or J0030 for short). They found it to be about 1.4 times the mass of the sun and about 16 miles across – pretty typical for neutron stars.
More recently, they applied the same technique to the neutron star PSR J0740+6620 (J0740 for short), the most massive known neutron star.
Despite J0740 weighing 50% more than J0030, it was almost the exact same size. The new results suggest that neutron stars aren’t very squishy: when adding mass, they don’t tend to squeeze down to smaller volumes.
“Our new measurements of J0740 show that even though it’s almost 50% more massive than J0030, it’s essentially the same size,” Watts said. “That challenges some of the more squeezable models of neutron star cores, including versions where the interior is just a sea of quarks. J0740’s size and mass also pose problems for some less squeezable models containing only neutrons and protons.”
“We’re surrounded by normal matter, the stuff of our everyday experience, but there’s much we don’t know about how matter behaves, and how it is transformed, under extreme conditions,” said Zaven Arzoumanian, the NICER science lead at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “By measuring the sizes and masses of neutron stars with NICER, we are exploring matter on the verge of imploding into a black hole. Once that happens, we can no longer study matter because it’s hidden by the black hole’s event horizon.”
While the new observations do rule out some models of neutron star interiors, there’s still a lot more work to do.
“J0740’s size has us theorists baffled and excited,” said Sanjay Reddy, a professor of physics at the University of Washington who studies matter under extreme conditions but was not involved in the finding. “NICER’s measurements, combined with other multimessenger observations, seem to support the idea that pressure increases rapidly in massive neutron star cores. While this disfavors transitions to more squeezable forms of matter in the core, its implications are yet to be fully understood.”
The May Moon Meets Venus and Mercury, at dusk en route to eclipse season and more.
Wonder where all the solar system action is hiding? While the dusk sky may seem devoid of planets (save for Mars), that’s all about to change this evening. The watch-phrase for astronomy in May 2021 is to ‘follow the Moon’ as it makes several spectacular planetary passes, then kicks off the first eclipse season of the year.
First up, the slim waxing crescent Moon occults the bright planet Venus tonight on May 12th. Though this occurs over the South Pacific and most of us will miss the actual event, the two will nestle very close to each other on the evening of Wednesday May 12th, making for a very photogenic pair. Ashen light or Earthshine on the dark limb of the Moon (caused by sunlight reflected off of the Earth) will give the scene an overall, 3-D appearance.
-3.9 magnitude Venus will actually make a great guide on the night of May 12th to spot the ethereal slim crescent Moon. Sure, Venus is tiny, at 10” across and 98% illuminated, versus the Moon’s 29.5’ apparent diameter and 1.2% illumination… but Venus is intrinsically brighter, bright enough that you can actually see it in the daytime near greatest elongation from the Sun… if you know exactly where in the sky to look for it. Your next chance to try this out in 2021 is on October 29th, when Venus sits 47 degrees east of the Sun, and dominates the dusk sky.
Now, see that zero magnitude ‘star’ above the Venus-Moon pair tonight? That’s the innermost planet Mercury. In fact, Mercury is headed towards one of its best apparitions for northern hemisphere observers for 2021 this month, reaching 22 degrees east of the Sun on May 17th. After that, Mercury losses altitude night after night while Venus gains prominence, until the two switch places on the night of May 29th, when the two planets sit in the same telescopic field of view just 24’ apart, less than the diameter of a Full Moon.
Follow that Moon as it waxes, and passes 1.5 degrees from +1.6 magnitude Mars on the evening of May 16th.
Tonight’s first sighting of the slim crescent Moon also marks the end of the fasting month of Ramadan for Muslims worldwide, and the start of the celebration of Eid al-Fitr. The Muslim calendar is based solely of the lunar cycle, meaning that months like Ramadan move forward 11 days versus the solar-based, Gregorian calendar. Other hybrid systems—such as the Hebrew or Chinese calendars—rely on both solar and lunar cycles, and must therefore add an extra or ‘embolismic’ month once every 2-3 years to stay in sync.
The Moon also just passed its most distant apogee (its ‘farthest-far point’ from the Earth) for 2021 at 406,511 kilometers distant on May 11th. This also sets us up for two interesting astronomical events in the coming weeks:
The first is the total lunar eclipse of May 26th. This will favor the Pacific region, with a maximum totality of 14 minutes and 30 seconds in duration. This also falls near the closest perigee (the ‘nearest-near point’ for the Moon to the Earth) for 2021 just 10 hours prior, at 357,309 kilometers distant. No doubt, the ‘Super-Blood Moon’ meme will once again sweep the internet.
Then, two weeks later, the Moon will be near apogee once again and will be too small to cover the Sun during the annular solar eclipse on June 10th. Annularity for this eclipse will sweep out through central Canada northeast across Hudson Bay, though much of northeastern North America will be treated to a fine rising partial solar eclipse at dawn.
Can’t wait ‘til June? If you live on the U.S. Eastern Seaboard, one other intriguing space event may head skyward tonight: watch for the launch of a sub-orbital Black Brant XII rocket from NASA Wallops in Virginia, with the KiNET-X experiment. The KiNETic-scale energy and momentum transport eXperiment will release barium vapor chemical tracers about 10 minutes after launch, in an effort to map and understand how energy transfer occurs in the Earth’s upper atmosphere. These sorts of launches are always tough to get off the pad, as skies much not only be clear at the Wallops launch site, but also at the Bermuda tracking station down range observing the experiment. A similar mission out of Wallops a few years back took weeks to launch. Another, dubbed AZURE, launched in 2019 out of Andoya Space Center in the high Scandinavian Arctic, with similarly eerie results. KiNET-X has a 40 minute launch window tonight, starting at 8:06 PM EDT/00:06 UT.
We’ll be tweeting as @Astroguyz about these celestial sky events, launches and more. Watch for full guides to each eclipse in the coming weeks, right here on Universe Today.
-Lead image credit: The Moon meets Venus in 2016. Image credit and copyright: Sharin Ahmad.
What’s better than a quasar? That’s right, two quasars. Astronomers have spotted for the first time two rare double-quasars, and the results show us the dynamic, messy consequences of galaxy formation.
Every galaxy is thought to host a supermassive black hole in its center. When galaxies merge, their black holes merge along with them. During the height of the merger process, huge volumes of gas and dust swirl down to the center of the galaxy. As all that gas and dust compresses down into the black hole, it heats up.
The forces are so intense that the cores of these galaxies become “quasars”, blazing brighter than millions of normal galaxies put together and beaming massive jets of radiation thousands of lightyears into space.
Astronomers have long observed many of these quasars, and many more normal galaxies. But double quasars? These would represent galaxies in a state of mid-merger, where gas and dust has compressed onto the core but the black holes themselves have not yet merged. Since it’s such a brief phase of the merger evolution, astronomers had not yet observed any.
“We estimate that in the distant universe, for every 1,000 quasars, there is one double quasar. So finding these double quasars is like finding a needle in a haystack,” said lead researcher Yue Shen of the University of Illinois at Urbana-Champaign.
The astronomers devised a technique that looked for subtle flickers in the brightness of quasars, a sign that the light we see may be from two competing cores rather than a single unified black hole. With the two sets of doubles on hand, astronomers can begin to directly probe this extremely violent phase of galaxy evolution.
“This truly is the first sample of dual quasars at the peak epoch of galaxy formation with which we can use to probe ideas about how supermassive black holes come together to eventually form a binary,” said research team member Nadia Zakamska of Johns Hopkins University in Baltimore, Maryland.
“Quasars make a profound impact on galaxy formation in the universe,” Zakamska said. “Finding dual quasars at this early epoch is important because we can now test our long-standing ideas of how black holes and their host galaxies evolve together.”
With the new technique, hopefully astronomers can catch a lot more quasars in the act. Their Nature Astronomy article is a “proof of concept that really demonstrates that our targeted search for dual quasars is very efficient,” said team member Hsiang-Chih Hwang, a graduate student at Johns Hopkins University and the principal investigator of the Hubble program. “It opens a new direction where we can accumulate a lot more interesting systems to follow up, which astronomers weren’t able to do with previous techniques or datasets.”
Things have been heating up lately over at Blue Origin, the commercial spaceflight company launched by Amazon founder Jeff Bezos. Since Bezos stepped down as CEO of Amazon to take a more hands-on role with his other projects, the company has made some rather positive strides. This includes a “dress rehearsal” test flight that took place on April 14th and brought their New Shepard a step closer to bringing passengers to space.
Following the success of this flight, Blue Origin recently announced they are planning to conduct the first crewed flight with the New Shepard by July 20th. In addition to the Blue Origin astronaut crew, one seat is being set aside for a commercial passenger. As of May 5th, Blue Origin announced that this ticket will be available for auction and that the proceeds will be donated to Blue Origin’s foundation, Club for the Future.
The announcement coincided with the 60th anniversary of the first crewed flight to space by an American astronaut. The astronaut in question was none other than the namesake of the Blue Origin spacecraft – Alan Shepard, who flew to space on May 5th, 1961 aboard the Freedom 7 capsule as part of the Project Mercury. Shepard was the first of seven astronauts (the Mercury Seven) who would go to space between 1961 and 1963.
Shepard would also go on to command the Apollo 14 mission and was one of the two mission astronauts to walk on the Moon. Shepard passed away on July 21st, 1998, in Pebble Beach, California, having been diagnosed with leukemia two years before. His wife passed away a little over a month later, and both were cremated and their ashes were spread by Navy Helicopter over Stillwater Cove near their home.
As Ariane Cornell, Blue Origin’s director of astronaut sales said during a May 5th press conference:
“We are selling the very first seat on New Shepard. The auction is a five-week-or-so, three-phase process that starts today… Anybody can go onto Blue Origin dot com and register and start their bidding today… Let’s say, the most active bidders, they’re gonna be very clear on our radar, so when we do go to open up those tickets, we’ll know who to go to contact.”
Phase One of the auction began on May 5th with sealed online bidding, during which time all bids will be kept invisible on the auction website. As of May 19th, Phase Two (unsealed online bidding) will begin, where all bids will be visible and participants must exceed the highest bid to continue. Things will culminate on June 12th, when the winner will be announced during a live event shared online.
As they indicate on their website, the flight will take off from the company’s launch facility (Launch Site One) located near the town of Van Horn in West Texas. Once the launcher reaches an altitude of 6.7 km (22,000 feet), the crew capsule (dubbed RSS First Step Crew Capsule) will separate from the first-stage booster and the crew will experience about ten minutes of weightlessness.
A minute later, the capsule will reach its apogee of about 100 km (62 mi) above sea level, or just past the Kármán Line. The capsule will then deploy its parachutes and conduct a soft landing, the entire experience lasting about ten minutes. According to the Terms and Conditions of the auction, “the Astronaut” (the auction winner) will be required to undergo training at a Blue Origin facility – most likely the one located in Kent, Washington, or Culberson County, Texas.
They also specify physical requirements, include a height and weight range of 5’0” and 110 lbs to 6’4” and 223 lbs. During the flight, the Astronaut will also be responsible for fastening and unfastening themselves in less than 15 seconds during and after the ~3 minutes of weightlessness. They must also be capable of withstanding the threefold increase in weight that will accompany the 2 minutes of powered ascent, and the 5.5-fold increase that will accompany descent into the atmosphere.
Last, but not least, they need to be comfortable sitting in a capsule for up to 90 minutes (40 minutes planned) without a bathroom break. There’s no indication how much the ticket could go for just yet, but this while auctioning idea is an interesting approach. This set it apart somewhat from other space tourism ventures like Virgin Galactic, which charges $250,000 a seat for future flights on its suborbital spaceplane, the VSS Unity.
Over the years, Musk has offered projections on what a one-way trip to Mars with SpaceX could cost, with estimates varying from $200,000 to $500,000. There is also the proposed lunar flyby scheduled for 2023, where a Starship will transport Japanese fashion titan, billionaire, and art collector Yusaku Maezawa and a crew of selected artists around the Moon (aka. the Dear Moon campaign).
There’s also Inspiration4, a philanthropic contest intended to raise awareness and funds for St. Jude Children’s Research Hospital. It will also be the first all-civilian mission to space, with four crewmembers representing the ideals of leadership, hope, generosity, and prosperity. This contest is being funded by Jared Isaacman, billionaire and founder of Shift4 Payments, who will also be acting as the mission commander.
In other words, commercial spaceflight and space tourism have a reputation for being an exclusive playground for the super-rich (and for good reason!) But with time and investment, prices will fall and space will become much more accessible – which was the very reason why Bezos, Musk, Branson, and other commercial space leaders launched their companies in the first place.
For Blue Origin, this flight will also be the culmination of over a decade of work and more than a few setbacks. In recent years, the company has lost ground as development has stalled on its rockets while SpaceX (their chief competitor) has not only managed to secure lucrative government contracts, but have continually pushed the envelop in terms of reusability and competitively-priced launch services.
Bezos is looking to change that. The recent test flight of the New Shepard was a good first step. This upcoming flight and the auction leading up to it will be an excellent follow-through! In the meantime, interested parties should head over to Blue Origin’s website to read the Terms and Conditions and post their bids!
Two companies, OneWeb and SpaceX, are racing to put fleets of thousands of communication satellites into orbit. In March they had their first near-miss. Avoidance maneuvers were successful, but how many more close calls will they face in the future?
SpaceX has already launched over a thousand of its Starlink global broadband internet satellites, and competitor OneWeb has lofted 146 of its own. Both companies – and several others – are actively prepping for dozens of more launches and thousands of more satellites.
But while space is a big place, orbits are a precious resource, especially with so many satellites already up and so many more planned. Near-misses are unavoidable, as both companies found out on March 30th, when they received several “red alerts” from the US Space Force’s 18th Space Control Squadron, warning of a possible collision.
The red alert came just 5 days after OneWeb launched 36 satellites from Russia. While the OneWeb constellation orbits at a higher altitude than Starlink, they must pass through those orbits to get to their operational location.
The Space Force alert noted that two satellites would pass within 190 feet of each other – which isn’t a lot when both spacecraft are flying at thousands of miles per hour. The probability of collision was calculated to be 1.3%.
SpaceX claims it has an AI-powered automated collision avoidance system onboard its spacecraft, but the company strangely shut down its system and allowed OneWeb to alter the course of its satellite instead. SpaceX did not provide public commentary on the event.
The near-miss has renewed calls for more transparency, accountability, and coordination of orbital activities. There is no law or authority that forces companies or agencies to move their satellites in the case of a potential collision – just a desire not to wreck perfectly good hardware and contribute to the spread of pernicious space junk.
Still, no satellites were harmed in the event, which is a good thing.
“This event was a good example of how satellite operators can be responsible given the constraints of global best practices,” says Diana McKissock, the head of the Space Force 18th Space Control Squadron’s data sharing and spaceflight safety wing. “They shared their data with each other, they got in contact with each other, and I think in absence of any global regulation, that’s… the art of the possible.”
White dwarfs have some surprisingly strong magnetic fields, and one team of astronomers may have finally found the reason why. When they cool, they can activate a dynamo mechanism similar to what powers the Earth’s magnetic field.
Some white dwarfs have magnetic fields a million times stronger than the Earth, but the origins of those fields have been a mystery for astronomers ever since the discovery of the first magnetized white dwarf in the 1970’s. The biggest problem is that white dwarfs have all sorts of different magnetic fields – and some don’t have them at all.
New research published in Nature Astronomy, led Professor Dr. Matthias Schreiber from Núcleo Milenio de Formación Planetaria at Universidad Santa María in Chile, may provide an answer: dynamo processes inside white dwarfs can power up some pretty impressive magnetic fields.
Professor Boris Gänsicke of the Department of Physics at the University of Warwick, who contributed to the work, says: “We have known for a long time that there was something missing in our understanding of magnetic fields in white dwarfs, as the statistics derived from the observations simply did not make sense. The idea that, at least in some of these stars, the field is generated by a dynamo can solve this paradox. Some of you may remember dynamos on bicycles: turning a magnet produces electric current. Here, it works the other way around, the motion of material leads to electric currents, which in turn generate the magnetic field.”
To get a dynamo to work, you need a layer of convecting material. The churning, rotating material can take weak magnetic fields can fold them back on themselves, amplifying them.
“The main ingredient of the dynamo is a solid core surrounded by a convective mantle—in the case of the Earth, it is a solid iron core surrounded by convective liquid iron. A similar situation occurs in white dwarfs when they have cooled sufficiently,” explains Matthias Schreiber.
When a white dwarf first forms, it’s a hot, dense ball of liquid carbon and oxygen. But as it begins to cool, some of the carbon and oxygen forms a crystal lattice. That crystallized core forms the foundation on which a convective layer can sit. If the white dwarf accretes material from a nearby companion, it can begin to spin rapidly, powering up the dynamo.
“As the velocities in the liquid can become much higher in white dwarfs than on Earth, the generated fields are potentially much stronger. This dynamo mechanism can explain the occurrence rates of strongly magnetic white dwarfs in many different contexts, and especially those of white dwarfs in binary stars” Schreiber says.
Dynamo mechanisms are common throughout the universe, and this work shows how those mechanism may resolve this decades-old problem. “The beauty of our idea is that the mechanism of magnetic field generation is the same as in planets. This research explains how magnetic fields are generated in white dwarfs and why these magnetic fields are much stronger than those on Earth. I think it is a good example of how an interdisciplinary team can solve problems that specialists in only one area would have had difficulty with,” Schreiber adds.
Ever feel like no matter how far you fly you end up in the same spot? Ingenuity certainly does. The helicopter that has been making dozens of headlines lately for all of the firsts it is achieving as part of its mission on Mars so far has only returned back to its original take-off point. Named Wright Brothers Field, after the brothers who first brought controlled powered flight to Earth, it has been the site of all of Ingenuity’s firsts so far. But now the basic science of Ingenuity’s mission is over and it is time to start moving on, which it did last week to a new “air field”.
That air field hasn’t yet received a name, but is located about 130m (450 ft) south of the Wright Brothers field. Ingenuity first scouted the area and found it flat and clear of debris on one of its four earlier flights. The small helicopter set another altitude record of 10m (33ft) on the 108 second flight. While it wasn’t Ingenuity’s farthest flight (which clocked in at 266 meters round-trip), it was the first time the helicopter set down on terrain it had only scouted previously.
Ingenuity’s primary mission completed with data from five flights under its belt. Now the NASA team commanding it has switched into an operational demonstration mode. They want to prove how practical it is to send these kinds of flying robotic explorers to other worlds. And if the extended length of other exploration missions on Mars are any indication, it will have a while to go yet. However, Ingenuity does have two constraints – it has relatively small solar panels to recharge its battery, and it has to stay close to Perseverance for it’s communications and controls.
Currently Perseverance itself is driving south in short bursts to complete its primary scientific mission and collect Martian samples that will be picked up by a later sample return mission. So Ingenuity will occasionally hop along with its rover hub to maintain contact with its handlers at NASA.
With its primary job completed, any additional data the tiny helicopter is able to collect is an added bonus. While it’s unclear how many more such hops Ingenuity is capable of, it has already earned its place in the pantheon of great robotic space explorers.
It’s widely known by now that the “dark side” of the moon, made famous by Pink Floyd, isn’t actually dark. It gets as much sunlight as the side that is tidally locked facing Earth. However, it is dark in one very important way – it isn’t affected by radio signals emanating from Earth itself. What’s more, it’s even able to see radio waves that don’t make it down to Earth’s surface, such as those associated with the cosmic “Dark Ages” when the universe was only a few hundred million years old. Those two facts are the main reasons the far side of the moon has continually been touted as a potential location for a very large radio telescope. Now, a project sponsored by NASA’s Institute for Advanced Concepts (NIAC) has received more funding to further explore this intriguing concept.
The project, known as the Lunar Crater Radio Telescope (LCRT), is part of NIAC’s Phase II program, and recently received $500k in additional funding to push the project further towards becoming a fully fledged NASA mission. This isn’t the first time a radio telescope on the moon has been proposed. But the LCRT team, led by Saptarshi Bandyopadhyay at JPL, have suggested two new and interesting features that make their approach much more attractive than previous alternatives.
The first feature has to do with limiting the sheer amount of material that is needed to construct a radio telescope. LCRT’s proposed instrument would be a one kilometer wide circle in a three kilometer wide crater. Traditional radio telescopes, such as the Five-hundred-meter Aperture Spherical Telescope (FAST) and the recently destroyedArecibo Observatory use hundreds of radio-reflective panels to any signals to an observing platform suspended by cable above the receiving dish.
In order to complete a 1km wide telescope, thousands of reflecting panels would have to be created on Earth, launched into space, and then placed precisely where they need to go. That’s a lot of launches and a lot of weight, and it made the entire concept of a lunar radio telescope untenable.
Dr. Bandyopadhyay’s solution to this problem is to use a wire mesh instead of solid panels to reflect the radio waves to the antenna. This mesh would be much lighter, and less bulky, but will still need to be set precisely in order to work properly. For that, the team turned to their other novel solution – dual robots.
Roboticists at JPL, of which Dr. Bandyopadhyay is one, have been working on a concept called DuAxel. These robots have two separate configurations. In one, they look like a standard four wheeled rover. In the other, the two halves separate. One anchors itself to a specific point while the other uses a tether to ease itself into otherwise unreachable terrain.
Crater walls would likely be such unreachable terrain, so having a robot that is able to access both the bottom of the crater and up above the rim where any landed supplies would be located is invaluable to any such telescope mission. It would also allow the robots to mount the antenna, the critical sensing piece of the telescope, above the crater’s center by applying tension in the mounting wires and lifting it into position.
Some major hurdles still remain, two of which will be the focus of this Phase II NIAC grant. The first is the design of the wire mesh network. It’s physical structure has to be exactly right in order for the telescope to work properly. In addition, it must be able to withstand the extreme temperature differences on the moon, which swing between -173 C and +127 C. If the mesh warps even slightly, the whole project could fail.
DuAxels themselves pose another quandary – should they be automated or have some sort of human intervention. Are they the only tools needed for the massive undertaking of constructing the largest ever radio telescope?
While Dr. Bandyopadhyay and his team work out these questions other factors put a time limit on the possibility of constructing a telescope in this most unique of locations. Part of the appeal of the far side of the moon is its lack of interference from artificial radio sources. However, that silence is not guaranteed. Already there is a satellite orbiting there, and other missions could be planned in the near future that would add confounding signals to the data mix.
That being said, the LCRT is still a long way from reality, and in its press release NASA is quick to point out that it hasn’t been accepted as a full NASA mission. But the intent of the NIAC program is to develop concepts to the point where they could become one. With that in mind, the extra half a million dollars will keep pushing the concept forward and hopefully result in a Phase III grant, which would then transition into a fully fledged NASA program after an additional two years of study. Though it might take awhile, the benefits of having such a massive telescope in one of the most radio quiet place in the solar system cannot be understated.