NASA’s Curiosity Rover has been exploring Mars since 2012 and, more recently has found evidence of ice-free ancient ponds and lakes on the surface. The rover found small undulations like those seen in sandy lake-beds on Earth. They would have been created by wind-driven water moving back and forth across the surface. The inescapable conclusion is that the water would have been open to the elements instead of being covered by ice. The discovery suggests the ripples formed 3.7 billion years ago.
Mars it the fourth planet in our Solar System and the second smallest of all the major planets. It’s known for its strong red colour which is caused by iron oxide in the surface material. Classed as a terrestrial planet, Mars is similar in many ways to Earth with valleys, volcanoes and even evidence of dried up river beds. The similarities end there though with polar caps made mostly of carbon dioxide ice, an unbreathable atmosphere and a surface that is cold and dry. It’s always held a special fascination for us due largely to vague hints through the centuries of alien intelligent but more recently that it may have once been habitable.
Once such rover that has been exploring the Martian landscape is the Curiosity Rover that was sent by NASA in 2011. It arrived at Mars in August 2012 and has been exploring the region around Gale Crater ever since. The main objective of Curiosity is to investigate the climate and geology and to assess if it could support primative life in the past. To achieve that end, it’s equipped with an array of instruments from drills to collect soil samples, cameras and instruments to analyse atmospheric samples.
A paper recently published in the journal Science Advances by Caltech’s John Grotzinger, Harold Brown Professor of Geology and Michael Lamb, Professor of Geology shared their findings. They found two sets of what seem to be ancient wave ripples on the surface of Mars now thought to be dried up bodes of water with the ripples preserved in rock. The ripples are tiny undulations and are often seen in beaches and lake-beds on Earth as wind-driven water flows across the shallows. The team are particularly excited that this means the water was not frozen and was once open to the elements as liquid.
The ripples discovered by Curiosity in Gale Crater are the strongest evidence to date that there have been bodies of liquid water in the history of the red planet. Analysis of the rocks and ripples suggest they formed 3.7 billion years ago. It’s thought that the atmosphere and climate of Mars must have been far warmer than it is today and more dense. Dense enough to support liquid water in open air.
The team were able to create computer models from the ripples they found to attempt to discover the size of lake. The size of the ripples and separation helps to determine how much water was present. The ripple height of 6mm and 4 to 5 cm separation tells us that the lake was shallow, possibly even less than 2 metres deep. One of the sets of ripples known as the Prow outcrop was found in an area that was once wind blown dunes. The other set was found nearby in the sulcate-rich Amapari Marker Band of rocks. The two regions come from slightly different times telling us that the warm dense atmosphere occurred at multiple times or at least for a long period of time.
The discovery has been a massive help to Mars paleoclimate studies that have tried to map the changing conditions on Mars. NASA’s Opportunity rover was the first mission to discover ripples on the surface but the nature of the bodies of water was uncertain. This latest discovery has given a fascinating insight into the early conditions on Mars, with perhaps, bodies of liquid dotted across the landscape. Further investigation is needed to see how commonplace the ripples are.
Source : Signatures of Ice-Free Ancient Ponds and Lakes Found on Mars
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Gas is the stuff of star formation, and most galaxies have enough gas in their budget to form some stars. However, the picture is a little different for dwarf galaxies. They lack the mass required to hold onto their gas when more massive neighbouring galaxies are siphoning it off.
New research shows that even isolated dwarf galaxies with no overbearing galactic neighbours struggle to form stars. What’s going on?
The research is centred on ultra-faint dwarf (UFD) galaxies. These tiny galaxies are the faintest galaxies in the Universe and contain only a few hundred stars, up to about one thousand. UFDs also contain ample amounts of dark matter. They’re different from globular clusters because globulars contain tens of thousands up to millions of stars and have very little dark matter, maybe none at all.
Because they’re so faint, astronomers struggle to locate them. The ones that have been found are close to the Milky Way. However, that makes them difficult to study because their massive neighbour dominates them. The Milky Way’s gravity and hot corona can siphon the UFDs’ gas away, making it challenging to understand their natural evolution.
Astronomers working with the DECam and the Gemini South Telescope have successfully located three UFDs well beyond the Milky Way’s gravitational influence. Although they weren’t easy to find, astronomers have made significant discoveries about UFDs from them.
The results are in new research published in The Astrophysical Journal Letters. It’s titled “Three Quenched, Faint Dwarf Galaxies in the Direction of NGC 300: New Probes of Reionization and Internal Feedback.” The lead author is David Sand, an astronomer from the Steward Observatory at the University of Arizona.
Sand found the three UFDs during a painstaking manual search. The UFDs are so faint that algorithmic searches couldn’t detect them.
“It was during the pandemic,” recalled Sand. “I was watching TV and scrolling through the DESI Legacy Survey viewer, focusing on areas of sky that I knew hadn’t been searched before. It took a few hours of casual searching, and then boom! They just popped out.”
The three UFDs are in the direction of the spiral galaxy NGC 300 and the Sculptor constellation. They’re called Sculptor A, Sculptor B, and Sculptor C.
Sculptor A is about 1.35 Mpc away and is likely at the edge of the Local Group, similar to Tucana B. It’s not a direct satellite of NGC 300.
Sculptor B is about 2.48 Mpc away and is likely behind NGC 300.
Sculptor C is about 2.04 Mpc away and is a satellite of NGC 300.
All three UFDs share some characteristics. They contain mostly old, metal-poor stars, are quenched and do not form any new stars, contain no neutral atomic hydrogen (H i), and emit no UV. “None of the three dwarfs are detected in H i line emission in the H i Parkes All Sky Survey, suggesting that they are not gas rich,” Sand and his co-researchers explain in their paper.
The lack of H I and UV both indicate that the galaxies are quenched and star formation has ceased. “Any younger blue stellar population either has few stars associated with it or is below our detection limit,” the authors write.
The discovery of the Sculptor galaxies, as they’re called, supports theories that say UFDs are dead galaxies that ceased star formation a long time ago in the early Universe. So, finding these faint quenched galaxies is entirely expected.
The jarring thing about their discovery is that they’re isolated. They’re not in proximity to any other larger galaxies that could’ve stripped away their gas and quenched their star formation. “The three dwarf galaxies in this work are among the faintest quenched dwarfs discovered outside the Local Group,” the authors write.
“Many of the recently discovered faint dwarf galaxies beyond the Local Group show distinct signs of recent star formation, although a growing subset also appears to be quenched, with little to no recent star formation,” the authors explain. “The mix of stellar populations of faint dwarf galaxies in the “field” is a critical ingredient for understanding the role of reionization, stellar feedback, and ram pressure from the cosmic web in driving the evolution of the smallest galaxies.”
Finding these three UFDs is significant because of their isolation. Only one of them, Sculptor C, is clearly associated with the nearby NGC 300. Sculptors A and B are isolated. Studying them is an opportunity to learn more about how star formation is affected by internal feedback mechanisms in low-mass galaxies. It’s also an opportunity to learn more about ram-pressure stripping, which is when gas is removed from a galaxy through interactions with the surrounding medium and even cosmic reionization.
During cosmic reionization, also known as the Epoch of Reionization, light from the first stars and galaxies reionized the neutral hydrogen in the intergalactic medium. The high-energy UV photons from the stars and galaxies could’ve effectively boiled away the gas in dwarf galaxies, ending their star formation.
An alternative explanation for UFDs losing their gas is supernova explosions. If some of the first stars in UFDs exploded, they could have expelled the gas and ended star formation. Ram-pressure stripping could also have been responsible.
Astronomers still need to learn more about reionization and if it’s responsible, and the Sculptor galaxies can help them.
“We don’t know how strong or uniform this reionization effect is,” explained Sand. “It could be that reionization is patchy, not occurring everywhere all at once. We’ve found three of these galaxies, but that isn’t enough. It would be nice if we had hundreds of them. If we knew what fraction was affected by reionization, that would tell us something about the early Universe that is very difficult to probe otherwise.”
“The Epoch of Reionization potentially connects the current day structure of all galaxies with the earliest formation of structure on a cosmological scale,” said Martin Still, NSF program director for the International Gemini Observatory. “The DESI Legacy Surveys and detailed follow-up observations by Gemini allow scientists to perform forensic archeology to understand the nature of the Universe and how it evolved to its current state.”
Ultimately, astronomers need to find more of these isolated UFDs to constrain their findings.
“Many more faint and ultrafaint dwarf galaxies are predicted at the edges of the Local Group and in nearby, low-density environments, but initial efforts to find them have not always been successful,” the authors write in their conclusion. That only emphasizes the importance of this discovery.
“Several upcoming programs such as Euclid, the Roman Space Telescope, and the Rubin Observatory Legacy Survey of Space and Time are sure to find many more examples in the years ahead, which will provide demographic properties across environments,” the authors conclude.
Sand presented these results at the recent 245th Meeting of the American Astronomical Society. Find them at the 32:00 mark of this video.
The post The Star-Forming Party Ended Early in Isolated Dwarf Galaxies appeared first on Universe Today.
The ISS’s orbit is slowly decaying. While it might seem a permanent fixture in the sky, the orbiting space laboratory is only about 400 km above the planet. There might not be a lot of atmosphere at that altitude. However, there is still some, and interacting with that is gradually slowing the orbital speed of the station, decreasing its orbit, and, eventually, pulling it back to Earth. That is, if we didn’t do anything to stop it. Over the 25-year lifespan of the station, hundreds of tons of hydrazine rocket fuel have been carried to it to enable rocket-propelled orbital maneuvers to keep its orbit from decaying. But what if there was a better way – one that was self-powered, inexpensive, and didn’t require constant refueling?
A new paper from Giovanni Anese, a PhD student at the University of Padua, and his team focuses on such a concept. It uses a new idea called a Bare Photovoltaic Tether (BPT), which is based on an older idea of an electrodynamic tether (EDT) but has some advantages due to the addition of solar panels along its length.
The basic idea behind a BPT, and EDTs more generally, is to extend a conductive boom out into a magnetic field and use the natural magnetic forces in the environment to provide a propulsive force. Essentially, it deploys a giant conductive rod into a magnetic field and uses the force on an electric field created in that rod to transfer force to where the rod is connected. It’s like the wind picking up an umbrella if the umbrella were a massive conductive rod and the wind were the planet’s natural magnetic field.
Electrodynamic tethers are not a new concept. They were initially introduced in 1968 by Giuseppe Colombo and Mario Grossi at Harvard’s Center for Astrophysics. Several demonstration missions have already taken flight, such as the TSS-1R that launched on the Space Shuttle Atlantis in 1996 and successfully deployed a 10-km long tether from the shuttle. Another experiment called the Plasma Motor Generator took place on the Russian space station Mir in 1999, which, instead of using an electromotive force to prove orbital stationkeeping, generated power directly from the tether itself.
Engineers have long considered using an EDT to perform stationkeeping duties on the ISS. However, a technical quirk made it impractical. To get the right sort of forces, the tether would need to be pointed “downward” toward the Earth or “upward” away from the planet.
No matter the direction in which the tether is pointed, it will still require power to operate. Without its magnetic field, caused by the electrical current running through it, it would act as a further drag rather than a boost. Therefore, a traditional EDT must be tied to a power system. However, if an EDT is deployed upward on the ISS, this power system would inhibit the approach corridors of capsules attempting to dock with the station.
This necessitates a downward-facing EDT so it can be connected to the ISS’s power system. While that does work, according to a prior paper published by the authors, it is less than ideal as downward-facing tethers are typically used in de-orbiting maneuvers rather than orbit-boosting ones.
Enter the BPT. The main difference between it and a traditional EDT is that its surface is at least partially covered in solar panels. If there are enough of them, these solar panels can completely power the system, allowing an upward-facing BPT to operate without being tied into the ISS’s power grid and keeping the approach lanes clear for arriving spacecraft.
Mr. Anese and his team studied different options in terms of length and solar panel coverage, disregarding the tether’s weight, as the difference in weight between the tether and the ISS itself was several orders of magnitude. They found that they could counteract the relatively small force that causes a 2km/month orbital drop from the ISS by utilizing a 15 km long tether around 97% covered in solar panels, at least on one side.
A 15 km tether might sound absurdly long, and admittedly, if pointing back to the Earth, it would cover a relatively large percentage of the total distance back to the ground. However, it is well within the realm of technological feasibility, especially given that Atlantis deployed that 10 km tether almost 30 years ago.
To prove their point, the authors turned to a software package called FLEXSIM, which allowed them to simulate the orbital dynamics of an ISS attached to different lengths of BPT. The tethers they chose were only 2.5cm wide, and the solar panels were only 4.23% efficient, though that is likely affected by the fact they had to be small and flexible. With that length of solar panels, the system could provide 8.3 kW of power for the whole tether, enough to boost the ISS’s orbital path.
There are some nuances about the effects of solar activity on the forces contributing to the orbital boost, but overall, the system, at least in theory, does seem to work. However, much discussion around the ISS lately has been about its end of life, which could come as early as 2031. So, while there are still a few good years left in the station, it likely won’t benefit as much from the BPT system as it would have a few decades ago. That being said, there will likely be a replacement in orbit someday, and it could benefit from such a system from the outset, which could save hundreds of tons of fuel in orbit over its lifetime.
Learn More:
Anese et al – Bare Photovoltaic Tether characteristics for ISS reboost
UT – Satellites Equipped With a Tether Would be Able to De-Orbit Themselves at the end of Their Life
UT – A New Satellite Is Going to Try to Maintain Low Earth Orbit Without Any Propellant
UT – SpaceX Reveals the Beefed-Up Dragon That Will De-Orbit the ISS
Lead Image:
Force diagram of the BPT tether system on the ISS.
Credit – Anese et al.
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What came first, galaxies or planets? The answer has always been galaxies, but new research is changing that idea.
Could habitable planets really have formed before there were galaxies?
In the immediate aftermath of the Big Bang, there were no heavy elements. There was only hydrogen, which comprised about 75% of the mass, and helium, which comprised the remaining 25%. (There were probably also trace amounts of lithium, even beryllium.) There was nothing heavier, meaning there was nothing for rocky planets to form from. After a few hundred million years, the first stars and galaxies formed.
As successive generations of stars lived and died, they forged heavier elements and spread them out into the Universe. Only after that could rocky planets form, and by extension, habitable planets. That’s been axiomatic in astronomy.
However, new research that’s yet to be published suggests that habitable worlds could’ve formed in the early stages of the Cosmic Dawn, prior to galaxies forming. Its title is “Habitable Worlds Formed at Cosmic Dawn,” and it’s available at the pre-press site arxiv.org. The lead author is Daniel Whalen from the Institute of Cosmology and Gravitation at the University of Portsmouth in the UK.
The research hinges on primordial supernovae, the first stars in the Universe to explode. These massive stars lived fast and died young in cataclysmic explosions. They peaked at about redshift 20 when population III stars, which were extremely massive, exploded as pair-instability supernovae. Simulations show that these stars formed in dark matter haloes where the temperature allowed large amounts of molecular hydrogen to gather.
According to Whalen and his co-researchers, when these stars exploded, low-mass stars formed in the aftermath. Planetesimals formed around those stars, leading to the formation of potentially habitable, rocky worlds. This all happened before the first galaxies formed. These results are based on simulations the research team performed with Enzo.
It starts with a star forming with about 200 solar masses. It lives for only about 2.6 million years before it explodes as a PI supernova. The explosion enriches the supernova bubble to high metallicity. In the aftermath, hydrostatic instabilities cause a dense core to form about 3 million years later, with 35 solar masses.
“All known prerequisites for planet formation in this core are fulfilled: dust growth, dust enhancement in a dead zone, the onset of the streaming instability, and conversion of dust to planetesimals,” the authors explain.
Here’s where this study differs from previous ones. Since the PI supernova explodes and creates high-metallicity gas, the gas cools more quickly. That allows the next star to form sooner, and hence, planetesimals and planets.
Eventually, a protostar with 0.3 solar masses formed. Then planetesimals formed between 0.46 and 1.66 AU from their star. Life needs water, and the researchers’ simulations also showed that the young solar system contained an amount of water similar to our own Solar System.
Planetesimals formed in the circumstellar disk around the low-mass star, and over time, they combined to form planets. Since the original primordial supernovae created elements like carbon, oxygen, and iron, all of the necessary ingredients were likely present to form rocky planets, even life.
The remarkable part is that this could’ve happened before the first galaxies formed. If true, it would change our understanding of the Universe and of life. However, this is just one simulation. How could observations support it?
“These planets could be detected as extinct worlds around ancient, metal-poor stars in the Galaxy in future exoplanet surveys,” Whelan and his fellow researchers write in their paper.
According to the authors, if conditions were just right, rocky planets could have formed even earlier than their simulations show. If that’s true, then it changes the entire course of events in the evolution of the Universe.
However, this is only a single study. And it hinges on primordial supernovae. Did they even exist? There’s at least some evidence that they did.
Clearly, attempting to observe primordial supernovae is extremely difficult. They occurred so long ago that they’re extraordinarily distant and faint. It’s likely impossible with current technology.
Also, there is much uncertainty about the Population III stars that were the progenitors of primordial supernovae. Their exact masses, lifetimes, and explosion mechanisms are uncertain. Astronomers don’t have a clear understanding of the early Universe’s extreme conditions. It’s still evolving, as is our understanding of supernovae. Combined, that’s a lot of uncertainty.
Still, all of these challenges don’t mean that primordial supernovae didn’t exist. So astronomers can’t rule them out, nor can they rule out very early habitable planets.
As things stand, there’s no way to prove or disprove this research. However, it does open another line of thinking and new possibilities.
The post Habitable Worlds Could Have Formed Before the First Galaxies appeared first on Universe Today.
The Andromeda galaxy is our closest galactic neighbour, barring dwarf galaxies that are gravitationally bound to the Milky Way. When conditions are right, we can see it with the naked eye, though it appears as a grey smudge. It’s the furthest object in the Universe that we can see without telescopic help.
The Hubble Space Telescope has created a massive 2.5-gigapixel panorama of Andromeda. It took 10 years and more than 1,000 orbits to capture all of the images.
We’re stuck inside the Milky Way and will never escape it. (Yes, there’s a tiny possibility we will in some far-off future.) The ESA’s powerful Gaia telescope has given us our best look at our own galaxy from inside it, but even it has its limitations.
That’s one of the reasons that observing Andromeda, also known as M31, is important. Like the Milky Way, M31 is also a barred spiral. By observing M31 in detail, we can learn more about our own galaxy. M31 is like a proxy for the Milky Way, and astronomers’ chief tool for studying our galactic proxy is the Hubble.
“With Hubble we can get into enormous detail about what’s happening on a holistic scale across the entire disk of the galaxy. You can’t do that with any other large galaxy,” said principal investigator Ben Williams of the University of Washington.
The image is a mosaic comprising at least 2.5 billion pixels. It resolves about 200 million individual stars, all of them hotter than our Sun. That’s only a small fraction of the galaxy’s stellar population, as dim stars like red dwarfs aren’t detected. The image contains bright blue star clusters, background galaxies, foreground stars, satellite galaxies, and dust lanes.
This vast image is the result of two observing programs: the Panchromatic Hubble Andromeda Southern Treasury (PHAST) and the Panchromatic Hubble Andromeda Treasury (PHAT). PHAT and PHAST have made a large contribution to galactic science. PHAT started acquiring the images for this mosaic about a decade ago, and now we have this new image thanks to both efforts.
New research in the Astrophysical Journal presents the latest results from PHAST, including the new image. It’s titled “PHAST. The Panchromatic Hubble Andromeda Southern Treasury. I. Ultraviolet and
Optical Photometry of over 90 Million Stars in M31.” the lead author is Zhuo Chen from the Department of Astronomy at the University of Washington in Seattle.
Andromeda is not only our nearest neighbour but also the nearest spiral to us and the largest galaxy in the Local Group. Those facts aren’t just answers to trivia questions. They explain why astronomers can study the galaxy in detail, including assessing its stellar population, without some of the problems they face observing other galaxies.
“M31 studies circumvent complications from line-of-sight reddening, uncertain distances, and background/foreground confusion,” the researchers write in their paper. “Furthermore, such studies can be put into the context of the surrounding local environment, such as the ISM structure, the star formation rate (SFR), and the metallicity of the stars and gas, and even larger environment as mapped by
the Pan-Andromeda Archeological Survey.”
“Thus, M31 provides a unique and interesting comparison to the detailed information we have for our
Milky Way,” the authors explain.
One of the main takeaways from this massive observing effort is that the southern disk, which hadn’t been studied as intently as the northern disk, is fundamentally different from its counterpart. The southern disk appears to be more disturbed, indicating that it shows the effects of M31’s merger history more than the northern disk. The presence of M32, an early-type dwarf galaxy, hints at some of that merger history.
Astronomers think that M32 could be what’s left of a galaxy that merged with Andromeda. Its properties are difficult to explain with our galaxy formation models. It could be the remnant core of a much more massive galaxy that was absorbed by Andromeda about two or three billion years ago.
“Andromeda’s a train wreck. It looks like it has been through some kind of event that caused it to form a lot of stars and then just shut down,” said study co-author Daniel Weisz at the University of California, Berkeley. “This was probably due to a collision with another galaxy in the neighborhood.”
One strong piece of evidence for that merger is the Giant Southern Stream. It’s a tidal debris stream made up of stars in Andromeda’s halo that could be a remnant from the ancient merger. The metallicity of its stars is generally lower than the stars in Andromeda’s bulge and disk.
The only way to understand Andromeda’s history is by surveying its stars. Thanks to PHAT and PHAST, astronomers now know 200 million individual stars. The observations are limited to stars brighter than the Sun, but the images are still scientifically rich. Together, they hint at a galaxy in transition.
“Andromeda looks like a transitional type of galaxy that’s between a star-forming spiral and a sort of elliptical galaxy dominated by aging red stars,” said Weisz. “We can tell it’s got this big central bulge of older stars and a star-forming disk that’s not as active as you might expect given the galaxy’s mass.”
“This detailed look at the resolved stars will help us to piece together the galaxy’s past merger and interaction history,” added PHAST’s Principal Investigator Ben Williams.
PHAST, together with PHAT, is a rich resource for astronomers studying Andromeda and, by extension, barred spirals everywhere, including our own Milky Way. However, before long, astronomers will get even better looks at Andromeda.
If all goes well, NASA will launch the Nancy Grace Roman Space Telescope in the near future. It’s an infrared telescope with a wide field of view, though it has the same size mirror. In a single exposure, the Roman can capture the equivalent of 100 high-resolution Hubble images, maybe more. It will help astronomers study the Giant Southern Stream in detail, along with other things, and will provide critical clues to Andromeda’s history.
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There’s a Universe full of black holes out there, spinning merrily away—some fast, others more slowly. A recent survey of supermassive black holes reveals that their spin rates reveal something about their formation history.
If you want to describe a supermassive black hole’s characteristics, there are two important numbers to use. One is its mass and the other is its spin rate. Some black hole spin rates are thought to be very close to the speed of light. According to Logan Fries, a PhD student at the University of Connecticut, those numbers are tough to get. “The problem is that mass is hard to measure, and spin is even harder,” he said. Yet, having accurate numbers is important if we want to understand black hole evolution.
Fries and his colleagues in the Sloan Digital Sky Survey’s Reverberation Mapping Project took on a tough job. They measured the spin rates of black holes over cosmic history. “We have studied the giant black holes found at the centers of galaxies, from today to as far back as seven billion years ago,” said Fries, a primary author of a paper about this work. The mapping project also made detailed observations of the associated accretion disks. Those are the areas nearest the black hole where matter accumulates and heats up as it spirals in. Measuring that region is important since knowing the black hole’s mass and its accretion disk’s structure provides data that allows them to measure the spin rate. Astronomers typically estimate the spin rate by observing how matter behaves as it falls into the black hole.
The results of the SDSS Survey of mass measurements of hundreds of black holes were a surprise, according to Fries. That’s because the spin rates reveal something about the black holes’ formation history. “Unexpectedly, we found that they were spinning too fast to have been formed by galaxy mergers alone,” he said. “They must have formed in large part from material falling in, growing the black hole smoothly and speeding up its rotation.”
Fries described his work at a recent meeting of the American Astronomical Society. “I have read research papers that examine black hole spin, theoretically, from the lens of like black hole mergers, and I was curious if spin could be observationally measured,” said Fries. He pointed out that the history of black hole growth requires more precise measurements than have been available. And, they’re not easy, according to Fries’s thesis advisor, Physics professor Jonathan Trump. “The challenge lies in separating the spin of the black hole from the spin of the accretion disk surrounding it,” said Trump. “The key is to look at the innermost region, where gas is falling into the black hole’s event horizon. A spinning black hole drags that innermost material along for the ride, which leads to an observable difference when we look at the details in our measurements.”
Digging into the mass and spin of a black hole requires spectral measurements. Those made by the SDSS contain subtle shifts in the spectra toward shorter wavelengths of light. That shift is a major clue to the black hole’s rotation rate. “I call this approach ‘black hole archaeology,'” said Fries “because we’re trying to understand how the mass of a black hole has grown over time. By looking at the spin of the black hole, you’re essentially looking at its fossil record.”
So, what does that fossil record tell us? First of all, it challenges the prevailing wisdom that black holes are always created in galaxy collisions. In other words, when galaxies merged, so did their central black holes. Each galaxy brings a rotation rate and orientation to the merger. The rotations could just as easily cancel each other out as they are to add together. If that is true, then the astronomers should have seen a wide range of spins. Some black holes should have a lot of spin, others… not so much.
The big surprise is that many black holes appear to spin very quickly. Even more amazing, the most distant ones seem to be spinning faster than the ones nearest to us (i.e. the “nearby” Universe). It’s as if they spin faster in the early Universe, and more slowly in more recent epochs. “We find that about 10 billion years ago, black holes acquired their mass primarily through eating things,” Fries explained.
The early fast spin rate implies that most supermassive black holes (like the one in our own Milky Way Galaxy) built up over time by taking in gas and dust in a very smooth and controlled manner. In other words, the more they eat (in the way of stars and gas), the faster their spin rate. It also turns out that merger growth actually slows the spin of supermassive black holes. That could explain why those we measure today have a mix of spin rates, rather than the more uniform rates of earlier epochs.
The idea of black holes forming smoothly over time provides a new direction for black hole research. Observations by JWST will help give more targets to study. Surveys such as the SDSS Reverberation Mapping project will follow up with more precise measurements of the huge supermassive black holes JWST continually finds as it studies the Universe.
Spinning Black Holes Reveal How They Grew
‘Black Hole Archaeology’: Understanding How Black Holes Gained Their Mass
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Supernovae are one of the most useful events in all of astronomy. Scientists can directly measure their power, their spin, and their eventual fallout, whether that’s turning into a black hole or a neutron star in some cases or just a much smaller stellar remnant. One of these events happened around 350 years ago (or around 11,000 years ago from the star’s perspective) in the constellation Cassiopeia. The James Webb Space Telescope recently caught a glimpse of the aftereffects of the explosion, and it happened to shed light (literally) on a familiar area of study – interstellar gas.
The supernova in Cassiopeia ejected a massive amount of X-rays and ultraviolet light into the area surrounding the now-dead star. That energy is now hitting a clump of gas gathered in the interstellar medium about 350 light years from the star. An effect called a “light echo” is created in the process.
A light echo can be thought of as a giant photographer’s bulb. A bright flash (i.e., the energy from the supernova) travels in an ever-extending sphere outwards, gradually illuminating everything in its path, then moving on and leaving the objects it just passed back in darkness. As the material is illuminated, telescopes back on Earth can see this otherwise invisible matter existing in the interstellar medium.
The Cassiopeia A explosion caused dozens of light echoes, but one in particular caught the attention of astronomers. From our perspective, gas and dust located past the now-dead star have been gradually lit up as the flash from the supernova passes through it, creating a spectacular image.
Spitzer, one of NASA’s great observatories that ended its observations in 2020, examined this same clump of gas and dust back in 2008. Its image was fascinating but not as complete as the one by its successor, JWST.
The image from JWST, admittedly falsely colored since humans can’t see infrared light, is spectacular, both aesthetically and scientifically. It shows a series of “sheets” that are remarkably small for an interstellar structure, measuring only about 400 AU across. They seem to be influenced by interstellar magnetic fields, as video of still images shows them twisting and writhing around.
Another feature of the image is described as “knots in wood grain” in a press release from the Webb telescope researchers. It also twists and moves over months as if dragged by some invisible force.
Light echoes can also be seen in the visible light range. However, infrared wavelengths, which are better thought of as the heat emitted from this gas and dust as the light echo passes through it, are more capable of showing the 3D structure as the wavelengths themselves aren’t blocked by the dust as visible light would be.
Consistently taking images over the course of months also provides another advantage. As Armin Rest of the Space Telescope Science Institute puts it, “We have three slices taken at three different times,” comparing the layered result as equivalent to a CT scan commonly used in medicine.
While the first picture from these studies might be fantastic, there is plenty of science left to do on these clouds of matter. Future work will continue to watch as the supernova flash-bulb illuminates and darkens different parts of the collected material. Some of that might even be destroyed, as the high-power supernovae that are strong enough to cause infrared light echoes could potentially vaporize some of the matter it hits.
JWST will continue to monitor the evolving situation, but a helping hand is coming. The Nancy Grace Roman Space Telescope, due to launch in 2027, will help scan the sky for evidence of other infrared light echoes. JWST will then follow up with closer observations using its powerful infrared instruments. If we’re lucky, we’ll see plenty more astonishing pictures soon, like the ones released last week.
Learn More:
Webb Space Telescope – NASA’s Webb Reveals Intricate Layers of Interstellar Dust, Gas
UT – A Fast-Moving Star is Colliding With Interstellar gas, Creating a Spectacular bow Shock
UT – Local Interstellar Gas Mapped in 3-D
UT – A Black Hole Has Cleared Out Its Neighbourhood
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The exoplanet census continues to grow. Currently, 5,819 exoplanets have been confirmed in 4,346 star systems, while thousands more await confirmation. The vast majority of these planets were detected in the past twenty years, owing to missions like the Kepler Space Telescope, the Transiting Exoplanet Survey Satellite (TESS), the venerable Hubble, the Convection, Rotation and planetary Transits (CoRoT) mission, and more. Thousands more are expected as the James Webb Space Telescope continues its mission and is joined by the Nancy Grace Roman Space Telescope (RST).
In the meantime, astronomers will soon have another advanced observatory to help search for potentially habitable exoplanets. It’s called Pandora, a small satellite that was selected in 2021 as part of NASA’s call for Pioneer mission concepts. This observatory is designed to study planets detected by other missions by studying these planets’ atmospheres of exoplanets and the activity of their host stars with long-duration multiwavelength observations. The mission is one step closer to launch with the completion of the spacecraft bus, which provides the structure, power, and other systems.
Funded by NASA’s Astrophysics Pioneers, Pandora is a joint effort between Lawrence Livermore National Laboratory in California and NASA’s Goddard Space Flight Center. The mission will study planets detected by other observatories that rely on Transit Photometry (aka. the Transit Method), where astronomers monitor stars for periodic dips in brightness that indicate the presence of orbiting planets. Pandora will then monitor these planets for future transits and obtain spectra from their atmospheres – a process known as Transit Spectroscopy.
Using this method, scientists can determine the chemical composition of exoplanet atmospheres and search for indications of biological activity (aka. “biosignatures”). During its year-long primary mission, the SmallSat will study 20 stars and their 39 exoplanets in visible and infrared light. The mission team anticipates Pandora will observe at least 20 exoplanets 10 times for 24 hours, during which transits will occur, and the satellite will obtain spectra from the exoplanets’ atmospheres.
In particular, Pandora will be looking to determine the presence of hazes, clouds, and water. The data it obtains will establish a firm foundation for interpreting measurements by Webb and future missions to search for habitable worlds. Daniel Apai, a co-investigator of the mission, is a professor of astronomy and planetary sciences at the U of A Steward Observatory and Lunar and Planetary Laboratory, who leads the mission’s Exoplanets Science Working Group. As he said in a U of A News release:
“Although smaller and less sensitive than Webb, Pandora will be able to stare longer at the host stars of extrasolar planets, allowing for deeper study. Better understanding of the stars will help Pandora and its ‘big brother,’ the James Webb Space Telescope, disentangle signals from stars and their planets.”
The concept for the telescope emerged to address a specific problem with Transit Spectroscopy. During transits, telescopes capture far more than just the passing through the planet’s atmosphere. They also capture light from the star itself. In addition, stellar surfaces are not uniform and have hotter, brighter regions (faculae) and cooler, darker regions (stellar spots) that change in size and position as the star rotates. This produces “mixed signals” that make it difficult to distinguish between light passing through the planet’s atmosphere and light from the star – which can mimic the signal produced by water.
Pandora will disentangle these signals by simultaneously monitoring the host star’s brightness in visible and infrared light. These observations will provide constraints on the variations in the star’s light, which can used to separate the star’s spectrum from the exoplanet’s. With the completion of the spacecraft bus, Pandora is one step closer to launch thanks to the completion of the spacecraft bus, which provides the structure, power, and other systems vital to the mission.
The completion of the bus was announced on January 16th during a press briefing at the 245th Meeting of the American Astronomical Society (AAS) in National Harbor, Maryland. “This is a huge milestone for us and keeps us on track for a launch in the fall,” said Elisa Quintana, Pandora’s principal investigator at NASA’s Goddard Space Flight Center. “The bus holds our instruments and handles navigation, data acquisition, and communication with Earth — it’s the brains of the spacecraft.” Said Ben Hord, a NASA Postdoctoral Program Fellow who discussed the mission at the 245 AAS:
“We see the presence of water as a critical aspect of habitability because water is essential to life as we know it. The problem with confirming its presence in exoplanet atmospheres is that variations in light from the host star can mask or mimic the signal of water. Separating these sources is where Pandora will shine.”
“Pandora’s near-infrared detector is actually a spare developed for the Webb telescope, which right now is the observatory most sensitive to exoplanet atmospheres. In turn, our observations will improve Webb’s ability to separate the star’s signals from those of the planet’s atmosphere, enabling Webb to make more precise atmospheric measurements.”
Unlike Webb and other flagship missions, Pandora can conduct continuous observations for extended periods because the demand for observation time will be low by comparison. Therefore, the Pandora satellite will fill a crucial gap between exoplanet discovery provided by flagship missions and exoplanet characterization. The mission is also a boon for the University of Arizona since Pandora’s science working group is led from there, and Pandora will be the first mission to have its operations center at the U of A Space Institute.
Further Reading: U of A News
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On Thursday, January 16th, at 02:03 AM EST, Blue Origin’s New Glenn rocket took off on its maiden flight from Launch Complex 36 at Cape Canaveral Space Force Station. This was a momentous event for the company, as the two-stage heavy-lift rocket has been in development for many years, features a partially reusable design, and is vital to Bezos’ plan of “building a road to space.” While the company failed to retrieve the first-stage booster during the flight test, the rocket made it to orbit and successfully deployed its payload -the Blue Ring Pathfinder – to orbit (which has since begun gathering data).
According to the most recent statement by Blue Origin, the second stage reached its final orbit following two successful burns of its two BE-3U engines. The successful launch of NG-1 means that Blue Origin can now launch payloads to Low Earth Orbit (LEO), a huge milestone for the commercial space company. “I’m incredibly proud New Glenn achieved orbit on its first attempt,” said Blue Origin CEO Dave Limp in a company statement. “We knew landing our booster, So You’re Telling Me There’s a Chance, on the first try was an ambitious goal. We’ll learn a lot from today and try again at our next launch this spring. Thank you to all of Team Blue for this incredible milestone.”
The rocket is named in honor of NASA astronaut John Glenn, a member of the Mercury 7 and the first American astronaut to orbit Earth as part of the Liberty Bell 7 mission on July 21st, 1961. This is in keeping with Blue Origin’s history of naming their launch vehicles after famous astronauts, such as the New Shepard rocket. This single-stage suborbital launch vehicle is named in honor of Alan Shepard, the first American astronaut to go to space as part of the Freedom 7 mission on May 5th, 1961.
Unlike the New Shepard, a fully reusable vehicle used primarily for space tourism and technology demonstrations and experiments, the New Glenn has a reusable first stage designed to land at sea on a barge named Jacklyn, or Landing Platform Vessel 1 (LPV1). While the second stage is not currently reusable, Blue Origin has been working on a reusable second stage (through Project Jarvis) since 2021. While development began on the New Glenn in 2013, the rocket has been stuck in “development hell” since 2016, shortly after it was first announced.
As a result, Blue Origin began lagging behind its main competitor (SpaceX) and missed out on several billion dollars worth of contracts. This included the company’s failure to secure a National Security Space Launch (NSSL) procurement contract and the U.S. Space Force’s termination of their launch technology partnership in late 2020. In 2021, the ongoing delay led to Jeff Bezos announcing that he would step down as CEO of Amazon Web Services (AWS) to take the helm at Blue Origin. By February 2024, the first fully-developed New Glenn rocket was unveiled at Launch Complex 36.
This mission not only validated the launch vehicle that is vital to the company’s future plans in space. It also served as the first of several demonstrations required to be certified for use by the National Security Space Launch program. “The success of the NG-1 mission marks a new chapter for launch operations at the Eastern Range, redefining commercial-military collaboration to maintain SLD 45’s position as the world’s premier gateway to space,” wrote Airman 1st Class Collin Wesson of the U.S. Space Force (USSF) Space Launch Delta 45 (SLD 45) Public Affairs, shortly after the launch.
These plans include the launch of Amazon’s proposed constellation of internet satellites (Project Kuiper) and the creation of the Orbital Reef – a proposed commercial space station under development by Blue Origin and Sierra Space. They have also secured a contract with NASA to launch the Escape and Plasma Acceleration and Dynamics Explorers (ESCAPADE) mission, two satellites that will study how solar wind interacts with Mars’ magnetic environment and drives atmospheric escape. NASA has also contracted with Blue Origin to provide payload and crewed launch services for the Artemis Program.
This includes the cargo lander Blue Moon Mark 1 and the Mark 2 that will transport the Artemis V astronauts to the lunar surface. This flight and those that will follow place Blue Origin among other commercial space companies poised to break up the near-monopoly SpaceX has enjoyed for over a decade. Said Jarrett Jones, the Senior VP for Blue Origin’s New Glenn:
“Today marks a new era for Blue Origin and for commercial space. We’re focused on ramping our launch cadence and manufacturing rates. My heartfelt thanks to everyone at Blue Origin for the tremendous amount of work in making today’s success possible, and to our customers and the space community for their continuous support. We felt that immensely today.”
Further Reading: Blue Origin
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Six or seven billion years ago, most stars formed in super star clusters. That type of star formation has largely died out now. Astronomers know of two of these SSCs in the modern Milky Way and one in the Large Magellanic Cloud (LMC), and all three of them are millions of years old.
New JWST observations have found another SSC forming in the LMC, and it’s only 100,000 years old. What can astronomers learn from it?
SSCs are responsible for a lot of star formation, but billions of years have passed since their heyday. Finding a young one in a galaxy so close to us is a boon for astronomers. It gives them an opportunity to wind back the clock and see how SSCs are born.
New research published in The Astrophysical Journal presents the new findings. It’s titled “JWST Mid-infrared Spectroscopy Resolves Gas, Dust, and Ice in Young Stellar Objects in the Large Magellanic Cloud.” The lead author is Omnarayani (Isha) Nayak from the Space Telescope Science Institute and NASA’s Goddard Space Flight Center.
At about 160,000 light-years away, the LMC is close in terms of galactic neighbours. It’s also face-on from our vantage point, making it easier to study. The N79 region in the LMC is a massive star-forming nebula about 1600 light-years across. The JWST used its Mid-Infrared Instrument (MIRI) and found 97 new young stellar objects (YSOs) in N79, where the newly discovered super star cluster, H72.97-69.39, is located.
Stellar metallicity increases over time as generations of stars are born and die. The LMC’s metallic abundance is only half that of our Solar System, meaning the conditions in the new SSC are similar to when stars formed billions of years ago in the early Universe. This is another of those situations in astronomy where studying a particular object or region is akin to looking into the past.
“Studying YSOs in the LMC gives astronomers a front-row seat to witness the birth of stars in a nearby galaxy. For the first time, we can observe individual low-mass protostars similar to the Sun forming in small clusters—outside of our own Milky Way Galaxy,” said Isha Nayak, lead author of this research. “We can see with unprecedented detail extragalactic star formation in an environment similar to how some of the first stars formed in the universe.”
The YSOs near the SSC H72.97-69.39 (hereafter referred to as H72) are segregated by mass. The most massive YSOs are concentrated near H72, while the less massive are on the outskirts of N79. The JWST revealed that what astronomers used to think were single massive young stars are actually clusters of YSOs. These observations confirm for the first time that what appear to be individual YSOs are often small clusters of protostars.
This finding brings attention to the complex processes of early star formation. “The formation of massive stars plays a vital role in influencing the chemistry and structure of the interstellar medium (ISM),” the authors write in their published research. “Star formation takes place in clusters, with massive stars dominating the luminosity.”
One of the five young stars is over 500,000 times more luminous than the Sun. As revealed by the JWST Near InfraRed Camera (NIRCam), it’s surrounded by more than 1,550 young stars.
Previous Atacama Large Millimeter/submillimeter Array (ALMA) observations hinted at what might contribute to the formation of SSCs. ALMA showed that colliding filaments of molecular gas at least one parsec long are in the region. These filaments could be behind H72’s formation.
This work highlights JWST’s power to resolve complex star formation locations in other galaxies. Not only did the JWST show us that what appeared to be individual YSOs are actually groups of stars, but it allowed the researchers to determine their mass accretion rates and chemical properties. The JWST’s new data gives astronomers new insights into complex chemistry, including the presence of organic molecules, dust, and ice in star-forming regions.
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