ST/ Scientists observe high-speed star formation

Paradigm

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Paradigm

32 min readFeb 23, 2023

Space biweekly vol.71, 9th February — 23rd February

TL;DR

New observations have brought to light that stars can form through the dynamic interaction of gas within interstellar gas clouds. This process unfolds faster than previously assumed, research within the FEEDBACK programme on board the flying observatory SOFIA revealed.
A peculiar cloud of gas, nicknamed the Tadpole due to its shape, appears to be revolving around a space devoid of any bright objects. This suggests that the Tadpole is orbiting a dark object, most likely a black hole 100,000 times more massive than the Sun. Future observations will help determine what is responsible for the shape and motion of the Tadpole.
Dust launched from the moon’s surface or from a space station positioned between Earth and the sun could reduce enough solar radiation to mitigate the impacts of climate change.
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) announced their first publicly released catalog of astronomical objects. Over 200,000 astronomical objects including distant stars and galaxies have been mapped in 3D for the first time. Astronomers will use the data to better determine the Hubble constant, used to gauge the expansion of the universe. Possible ‘naked black hole’ early highlight of science results from HETDEX survey. TACC systems Corral, Stampede2, and Maverick were used in the data analysis and storage. Data publicly available through JupyterHub notebooks.
New images of Saturn from NASA’s Hubble Space Telescope herald the start of the planet’s “spoke season” surrounding its equinox, when enigmatic features appear across its rings. The cause of the spokes, as well as their seasonal variability, has yet to be fully explained by planetary scientists.
Scientists have discovered a new ring system around a dwarf planet on the edge of the Solar System. The ring system orbits much further out than is typical for other ring systems, calling into question current theories of how ring systems are formed.
Astronomers have uncovered striking new evidence for a mass migration of stars into the Andromeda Galaxy. Intricate patterns in the motions of stars reveal an immigration history very similar to that of the Milky Way.
Scientists have found how the human brain changes and adapts to weightlessness, after being in space for 6 months. Some of the changes turned out to be lasting — even after 8 months back on Earth.
Mars is infamous for its intense dust storms, some of which kick up enough dust to be seen by telescopes on Earth. When dust particles rub against each other, as they do in Martian dust storms, they can become electrified. New research shows that one particularly efficient way to move chlorine from the ground to the air on Mars is by way of reactions set off by electrical discharge generated in dust activities.
When the Artemis 1 mission was launched in November, it became the world’s most powerful rocket, and with liftoff came a loud roar heard miles away. Researchers report noise measurements during the launch at different locations around Kennedy Space Center. The data collected can be used to validate existing noise prediction models, which are needed to protect equipment as well as the surrounding environment and community.
Upcoming industry events. And more!

Space industry in numbers

The global smart space market size is projected to grow from USD 9.4 billion in 2020 to USD 15.3 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 10.2% during the forecast period. The increasing venture capital funding and growing investments in smart space technology to drive market growth.

Analysts at Morgan Stanley and Goldman Sachs have predicted that economic activity in space will become a multi-trillion-dollar market in the coming decades. Morgan Stanley’s Space Team estimates that the roughly USD 350 billion global space industry could surge to over USD 1 trillion by 2040.

Source: Satellite Industry Association, Morgan Stanley Research, Thomson Reuters. *2040 estimates

Space industry news

Latest research

Ionized carbon as a tracer of the assembly of interstellar clouds

by Nicola Schneider, Lars Bonne, Sylvain Bontemps, Slawa Kabanovic, Robert Simon, Volker Ossenkopf-Okada, Christof Buchbender, Jürgen Stutzki, Marc Mertens, Oliver Ricken, Timea Csengeri, Alexander G.G.M. Tielens in Nature Astronomy

Even though SOFIA is no longer in operation, the data collected so far are essential for basic astronomical research because there is no longer an instrument that extensively maps the sky in this wavelength range (typically 60 to 200 micrometres). The now active James Webb Space Telescope observes in the infrared at shorter wavelengths and focuses on spatially small areas. Therefore, the analysis of the data collected by SOFIA is ongoing and continues to provide important insights — also regarding other star-forming regions: “In the list of FEEDBACK sources, there are other gas clouds in different stages of evolution, where we are now looking for the weak CII radiation at the peripheries of the clouds to detect similar interactions as in the Cygnus X region,” Schneider concluded.

The observations were carried out in an international project led by Dr Nicola Schneider at the University of Cologne and Prof Alexander Tielens at the University of Maryland as part of the FEEDBACK programme on board the flying observatory SOFIA (Stratospheric Observatory for Infrared Astronomy). The new findings modify previous perceptions that this specific process of star formation is quasi-static and quite slow. The dynamic formation process now observed would also explain the formation of particularly massive stars.

Velocity integrated CO and [CII] emission in the DR21, W75N and HV range.

By comparing the distribution of ionized carbon, molecular carbon monoxide and atomic hydrogen, the team found that the shells of interstellar gas clouds are made of hydrogen and collide with each other at speeds of up to twenty kilometres per second. “This high speed compresses the gas into denser molecular regions where new, mainly massive stars form. We needed the CII observations to detect this otherwise ‘dark’ gas,” said Dr Schneider. The observations show for the first time the faint CII radiation from the periphery of the clouds, which could not be observed before. Only SOFIA and its sensitive instruments were capable of detecting this radiation.

SOFIA was operated by NASA and the German Aerospace Center (DLR) until September 2022. The observatory consisted of a converted Boeing 747 with a built-in 2.7-metre telescope. It was coordinated by the German SOFIA Institute (DSI) and the Universities Space Research Association (USRA). SOFIA observed the sky from the stratosphere (above 13 kilometres) and covered the infrared region of the electromagnetic spectrum, just beyond what humans can see. The Boeing thus flew above most of the water vapour in the Earth’s atmosphere, which otherwise blocks out infrared light. This allowed the scientists to observe a wavelength range that is not accessible from Earth. For the current results, the team used the upGREAT receiver installed on SOFIA in 2015 by the Max Planck Institute for Radio Astronomy in Bonn and the University of Cologne.

Scatter plots and spectra of [CII] and CO 1 → 0 emission.

Even though SOFIA is no longer in operation, the data collected so far are essential for basic astronomical research because there is no longer an instrument that extensively maps the sky in this wavelength range (typically 60 to 200 micrometres). The now active James Webb Space Telescope observes in the infrared at shorter wavelengths and focuses on spatially small areas. Therefore, the analysis of the data collected by SOFIA is ongoing and continues to provide important insights — also regarding other star-forming regions: “In the list of FEEDBACK sources, there are other gas clouds in different stages of evolution, where we are now looking for the weak CII radiation at the peripheries of the clouds to detect similar interactions as in the Cygnus X region,” Schneider concluded.

Discovery of the Tadpole Molecular Cloud near the Galactic Nucleus

by Miyuki Kaneko, Tomoharu Oka, Hiroki Yokozuka, Rei Enokiya, Shunya Takekawa, Yuhei Iwata, Shiho Tsujimoto in The Astrophysical Journal

A peculiar cloud of gas, nicknamed the Tadpole due to its shape, appears to be revolving around a space devoid of any bright objects. This suggests that the Tadpole is orbiting a dark object, most likely a black hole 100,000 times more massive than the Sun. Future observations will help determine what is responsible for the shape and motion of the Tadpole.

A team of Japanese researchers led by Miyuki Kaneko at Keio University used data from the James Clerk Maxwell Telescope, operated by the East Asian Observatory, and NAOJ’s Nobeyama 45-m Radio Telescope to identify an unusual cloud of gas about 27,000 light-years away in the constellation Sagittarius. The curved “Tadpole” shape of the molecular gas cloud strongly suggests that it is being stretched as it orbits around a massive compact object. The only problem is, at the center of the Tadpole’s orbit, there are no bright objects which could be massive enough to gravitationally hold the Tadpole. The best candidate for this massive compact invisible object is a black hole.

Map of velocity-integrated CO J = 3–2 emission.

Because black holes don’t emit light, the only way to detect them is when they interact with other objects. This leaves astronomers in the dark about just how many black holes, and with what range of masses, might be lurking in the Milky Way.

Now the team plans to use ALMA (Atacama Large Millimeter/submillimeter Array) to search for faint signs of a black hole, or other object, at the gravitational center of the Tadpole’s orbit.

Dust as a solar shield

by Benjamin C. Bromley, Sameer H. Khan, Scott J. Kenyon in PLOS Climate

On a cold winter day, the warmth of the sun is welcome. Yet as humanity emits more and more greenhouse gases, the Earth’satmosphere traps more and more of the sun’s energy and steadily increases the Earth’s temperature. One strategy for reversing this trend is to intercept a fraction of sunlight before it reaches our planet. For decades, scientists have considered using screens, objects or dust particles to block just enough of the sun’s radiation — between 1 or 2% — to mitigate the effects of global warming.

A University of Utah-led study explored the potential of using dust to shield sunlight. They analyzed different properties of dust particles, quantities of dust and the orbits that would be best suited for shading Earth. The authors found that launching dustfrom Earth to a way station at the “Lagrange Point” between Earth and the sun (L1) would be most effective but would require astronomical cost and effort. An alternative is to use moondust. The authors argue that launching lunar dust from the moon instead could be a cheap and effective way to shade the Earth.

The team of astronomers applied a technique used to study planet formation around distant stars, their usual research focus. Planet formation is a messy process that kicks up lots ofastronomical dust that can form rings around the host star. These rings intercept light from the central star and re-radiate it in a way that we can detect it on Earth. One way to discover stars that are forming new planets is to look for these dusty rings.

“That was the seed of the idea; if we took a small amount of material and put it on a special orbit between the Earth and the sun and broke it up, we could block out a lot of sunlight with a little amount of mass,” said Ben Bromley, professor of physics and astronomy and lead author of the study.
“It is amazing to contemplate how moon dust — which took over four billion years to generate — might help slow the rise in Earth’s temperature, a problem that took us less than 300 years to produce,” said Scott Kenyon, co-author of the study from the Center for Astrophysics | Harvard & Smithsonian.

The attenuation from a monodisperse cloud of particles with total mass Mcloud = 109 kg at true L1 as a function of radius.

A shield’s overall effectiveness depends on its ability to sustain an orbit that casts a shadow on Earth. Sameer Khan, undergraduate student and the study’s co-author, led the initial exploration into which orbits could hold dust in position long enough to provide adequate shading. Khan’s work demonstrated the difficulty of keeping dust where you need it to be.

“Because we know the positions and masses of the major celestial bodies in our solar system, we can simply use the laws of gravity to track the position of a simulated sunshield over time for several different orbits,” said Khan.

Two scenarios were promising. In the first scenario, the authors positioned a space platform at the L1 Lagrange point, the closest point between Earth and the sun where the gravitational forces are balanced. Objects at Lagrange points tend to stay along a path between the two celestial bodies, which is why the James Webb Space Telescope (JWST) is located at L2, a Lagrange point on the opposite side of the Earth.

In computer simulations, the researchers shot test particles along the L1 orbit, including the position of Earth, the sun, the moon, and other solar system planets, and tracked where the particles scattered. The authors found that when launched precisely, the dust would follow a path between Earth and the sun, effectively creating shade, at least for a while. Unlike the 13,000-pound JWST, the dust was easily blown off course by the solar winds, radiation, and gravity within the solar system. Any L1 platform would need to create an endless supply of new dust batches to blast into orbit every few days after the initial spray dissipates.

“It was rather difficult to get the shield to stay at L1 long enough to cast a meaningful shadow. This shouldn’t come as a surprise, though, since L1 is an unstable equilibrium point. Even the slightest deviation in the sunshield’s orbit can cause it to rapidly drift out of place, so our simulations had to be extremely precise,” Khan said.

In the second scenario, the authors shot lunar dust from the surface of the moon towards the sun. They found that the inherent properties of lunar dust were just right to effectively work as a sun shield. The simulations tested how lunar dust scattered along various courses until they found excellent trajectories aimed toward L1 that served as an effective sun shield. These results are welcome news, because much less energy is needed to launch dust from the moon than from Earth. This is important because the amount of dust in a solar shield is large, comparable to the output of a big mining operation here on Earth. Furthermore, the discovery of the new sun-shielding trajectories means delivering the lunar dust to a separate platform at L1 may not be necessary.

The authors stress that this study only explores the potential impact of this strategy, rather than evaluate whether these scenarios are logistically feasible.

“We aren’t experts in climate change, or the rocket science needed to move mass from one place to the other. We’re just exploring different kinds of dust on a variety of orbits to see how effective this approach might be. We do not want to miss a game changer for such a critical problem,” said Bromley.

One of the biggest logistical challenges — replenishing dust streams every few days — also has an advantage. Eventually, the sun’s radiation disperses the dust particles throughout the solar system; the sun shield is temporary and shield particles do not fall onto Earth. The authors assure that their approach would not create a permanently cold, uninhabitable planet, as in the science fiction story, “Snowpiercer.”

“Our strategy could be an option in addressing climate change,” said Bromley, “if what we need is more time.”

HETDEX Public Source Catalog 1: 220 K Sources Including Over 50 K Lyα Emitters from an Untargeted Wide-area Spectroscopic Survey

by Erin Mentuch Cooper, Karl Gebhardt, Dustin Davis, et al in The Astrophysical Journal

Astronomers have barely scratched the surface of mapping the nearly endless stars and galaxies of the heavens. Using supercomputers, researchers with The University of Texas at Austin have has now revealed the locations of more than 200,000 new astronomical objects. Their goal is to map even more and use that knowledge to predict the ultimate fate of the universe.

The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) has scanned the dark skies of the Davis Mountains in West Texas since 2017 with a keen eye towards capturing spectroscopic data on Lyman-alpha frequency light from neutral hydrogen emission in galaxies over 10 billion light years away. These galaxies emit a signature wavelength of light from hydrogen that signals to astronomers the intense creation of new stars.

The HETDEX collaboration involves a large team including astronomers, engineers, technicians, and graduate students from six academic institutions in the United States and Germany. For the first time, the researchers have cataloged astronomical objects — mapping over 51,863 Lyman-alpha-emitting galaxies at high redshift; 123,891 star forming galaxies at lower redshift; 5,274 non-emission line galaxies at low redshift; and 4,976 active galactic nuclei (AGN) — bright spots that signal the presence of black holes.

Sky coverage of the planned HETDEX science fields (in red) and the footprint of this catalog release (in blue).

“We’ve just exploded in terms of the number of redshifts cataloged for the first time,” said study co-author Erin Mentuch Cooper, a research scientist at The University of Texas at Austin (UT Austin). Cooper is the data manager for the HETDEX project.
“There is a gold mine of astronomy exploration in the HETDEX catalog. That’s what I love about it,” said study co-author Karl Gebhardt, the Herman and Joan Suit Professor in Astronomy, College of Natural Sciences, UT Austin. Gebhardt is project scientist and principal investigator of HETDEX.

A star’s redshift tells astronomers how fast a star is moving away from the Earth because its frequency, akin to its color, gets lower as it moves away, much like the horn of a train as it passes by. The faster a star moves away, the farther away it is. That relationship between speed and distance, called Hubble’s Law, can pin down a galaxy’s location and allows astronomers to create a 3D map of over 200,000 stars and galaxies with HETDEX.

“This is only a small percentage of what we will find, but it’s a good start. Ultimately, HETDEX aims to map one million red-shifted galaxies,” Cooper said.

HETDEX is unique from previous large sky surveys because it’s a non-targeted survey, blanketing the sky and collecting spectra from the 35,000 fiber optic cables of the Visible Integral Field Replicable Unit Spectrograph (VIRUS). VIRUS takes starlight from distant galaxies and splits the light into its component colors like a prism does. HETDEX tiles the sky, collecting 35,000 spectra in a moon-sized swath of sky and moving from spot to spot. It collects about 500–600 hours of observations each year for its survey data.

“We have the largest spectroscopic instrument on the planet, and we’re doing one of the longest surveys in terms of time,” Gebhardt said. “To analyze this data, we need the fastest computer we can get our hands on, and that’s where TACC comes in. TACC does all the data storage and all the data analysis for this giant survey.”

Fiber layout for a typical three-dither HETDEX/VIRUS observation for a single 51'’ × 51'’ IFU is shown on the left panel.

The data from the telescope goes straight to the TACC Corral data storage system via high speed lines at 100 Gigabits/second.

“TACC has worked hard with us to streamline our system, and it’s just working fantastically. We can process years of data in a couple of days, maybe a week of time on TACC systems. And we do it multiple times because we keep adjusting and improving our methods,” Gebhardt added.

HETDEX used the Maverick and Stampede2 supercomputers of the Texas Advanced Computing Center, a leading academic supercomputing center at UT Austin. Stampede2 is funded by the National Science Foundation as a shared resource for thousands of scientists across the US. They helped process and analyze about 60 terabytes of image data on TACC’s Corral system. What’s more, Cooper and colleagues have worked with TACC to create JupyterHub public access to the data.

“Anyone with any academic credentials can get a TACC account and go on through a web browser to access our data. We’re going to let them access all of our data. This is just the catalog right now. But, the future is going to offer a legacy potential of the science from HETDEX. TACC is helping setting that up,” Cooper said.

One interesting highlight from the catalog is the identification of an active galactic nuclei (AGN) with strong Lyman-alpha light emission. Gebhadt co-authored a studyled by UT Austin astronomy post-doctoral researcher Chenxu Liu, published November 2022 in The Astrophysical Journal. It presents intriguing evidence of a black hole without a surrounding host galaxy.

“This is what I call ‘naked black holes,’” Gebhardt said. “Nothing confirmed yet, but we suspect these could be out there. Only a survey like HETDEX will be able to find these.”

The science generated from HETDEX adds to the bigger picture of understanding the expansion of the entire universe, unexpectedly growing much faster than expected based on precise observations from the Hubble Space Telescope in 2019 of supernovae that act like a cosmic yardstick. The Holy Grail for HETDEX is an accurate measure of the Universe expansion rate 10 billion years ago that will reveal the physical model for dark energy. Astronomers are at odds over how to explain the measure of the current expansion rate. Understanding it could require a modification in the theory of gravity, or a change in the fundamental Big Bang theory. It might be the handiwork of an undiscovered particle. A precise value of the expansion rate early in the Universe can be compared to the expansion rate today. This comparison can determine if the Universe will continue to expand forever, or will someday collapse on itself many billions of years from now.

“The whole point of the HETDEX project is to measure the expansion of the universe,” Gebhardt said.
“This new catalog adds valuable data in finally answering the ‘million galaxy’ question, which is something the HETDEX Collaboration is working very hard on in the coming year. But there’s a bigger picture here, and that’s what we give back to the community, not just to the scientists around the world but the general community. We wouldn’t be able to do this work without the supercomputing resources and experts at TACC, through allowing us the computing power to run many analyses of the data and continue to improve the process.”

Hubble Detects the Start of a New Saturn Ring Spoke Season

by Amy A. Simon, Matthew M. Hedman, Philip D. Nicholson, Matthew S. Tiscareno, Mark R. Showalter, Troy McDonald, Samantha Callos in Geophysical Research Letters

New images of Saturn from NASA’s Hubble Space Telescope herald the start of the planet’s “spoke season” surrounding its equinox, when enigmatic features appear across its rings. The cause of the spokes, as well as their seasonal variability, has yet to be fully explained by planetary scientists.

Like Earth, Saturn is tilted on its axis and therefore has four seasons, though because of Saturn’s much larger orbit, each season lasts approximately seven Earth years. Equinox occurs when the rings are tilted edge-on to the Sun. The spokes disappear when it is near summer or winter solstice on Saturn. (When the Sun appears to reach either its highest or lowest latitude in the northern or southern hemisphere of a planet.) As the autumnal equinox of Saturn’s northern hemisphere on May 6, 2025, draws near, the spokes are expected to become increasingly prominent and observable.

The suspected culprit for the spokes is the planet’s variable magnetic field. Planetary magnetic fields interact with the solar wind, creating an electrically charged environment (on Earth, when those charged particles hit the atmosphere this is visible in the northern hemisphere as the aurora borealis, or northern lights). Scientists think that the smallest, dust-sized icy ring particles can become charged as well, which temporarily levitates those particles above the rest of the larger icy particles and boulders in the rings.

Hubble 2021 spoke detection. Images acquired on 12 September 2021 show a faint dark feature that rotates with the rings over 30 min. Contrast has been enhanced, but the features are only a few percent darker than the rings themselves.

The ring spokes were first observed by NASA’s Voyager mission in the early 1980s. The transient, mysterious features can appear dark or light depending on the illumination and viewing angles.

“Thanks to Hubble’s OPAL program, which is building an archive of data on the outer solar system planets, we will have longer dedicated time to study Saturn’s spokes this season than ever before,” said NASA senior planetary scientist Amy Simon, head of the Hubble Outer Planet Atmospheres Legacy (OPAL) program.

Saturn’s last equinox occurred in 2009, while NASA’s Cassini spacecraft was orbiting the gas giant planet for close-up reconnaissance. With Cassini’s mission completed in 2017, and the Voyager spacecrafts long gone, Hubble is continuing the work of long-term monitoring of changes on Saturn and the other outer planets.

Cassini spoke detections in 2014. Sparse spokes appear as faint bright features in Cassini images of the unlit side of the rings.

“Despite years of excellent observations by the Cassini mission, the precise beginning and duration of the spoke season is still unpredictable, rather like predicting the first storm during hurricane season,” Simon said.

While our solar system’s other three gas giant planets also have ring systems, nothing compares to Saturn’s prominent rings, making them a laboratory for studying spoke phenomena. Whether spokes could or do occur at other ringed planets is currently unknown. “It’s a fascinating magic trick of nature we only see on Saturn — for now at least,” Simon said.

Hubble’s OPAL program will add both visual and spectroscopic data, in wavelengths of light from ultraviolet to near-infrared, to the archive of Cassini observations. Scientists are anticipating putting these pieces together to get a more complete picture of the spoke phenomenon, and what it reveals about ring physics in general.

A dense ring of the trans-Neptunian object Quaoar outside its Roche limit

by B. E. Morgado, B. Sicardy, F. Braga-Ribas, J. L. Ortiz, H. Salo, in Nature

Scientists have discovered a new ring system around a dwarf planet on the edge of the Solar System. The ring system orbits much further out than is typical for other ring systems, calling into question current theories of how ring systems are formed.

The ring system is around a dwarf planet, named Quaoar, which is approximately half the size of Pluto and orbits the Sun beyond Neptune. The discovery was made by an international team of astronomers using HiPERCAM — an extremely sensitive high-speed camera developed by scientists at the University of Sheffield which is mounted on the world’s largest optical telescope, the 10.4 metre diameter Gran Telescopio Canarias (GTC) on La Palma.

The rings are too small and faint to see directly in an image. Instead, the researchers made their discovery by observing an occultation, when the light from a background star was blocked by Quaoar as it orbits the Sun. The event lasted less than a minute, but was unexpectedly preceded and followed by two dips in light, indicative of a ring system around Quaoar.

Ring systems are relatively rare in the Solar System — as well as the well-known rings around the giant planets Saturn, Jupiter, Uranus and Neptune, only two other minor planets possess rings — Chariklo and Haumea. All of the previously known ring systems are able to survive because they orbit close to the parent body, so that tidal forces prevent the ring material from accreting and forming moons.

What makes the ring system around Quaoar remarkable is that it lies at a distance of over seven planetary radii — twice as far out as what was previously thought to be the maximum radius according to the so-called `Roche limit’, which is the outer limit of where ring systems were thought to be able to survive. For comparison, the main rings around Saturn lie within three planetary radii. This discovery has therefore forced a rethink on theories of ring formation.

Professor Vik Dhillon, co-author of the study from the University of Sheffield’s Department of Physics and Astronomy, said: “It was unexpected to discover this new ring system in our Solar System, and it was doubly unexpected to find the rings so far out from Quaoar, challenging our previous notions of how such rings form. The use of our high-speed camera — HiPERCAM — was key to this discovery as the event lasted less than one minute and the rings are too small and faint to see in a direct image.
“Everyone learns about Saturn’s magnificent rings when they’re a child, so hopefully this new finding will provide further insight into how they came to be.”

DESI Observations of the Andromeda Galaxy: Revealing the Immigration History of our Nearest Neighbor

by Arjun Dey, Joan R. Najita, S. E. Koposov, J. Josephy-Zack,et al in The Astrophysical Journal

Over the course of billions of years, galaxies grow and evolve by forging new stars and merging with other galaxies through aptly named “galactic immigration” events. Astronomers try to uncover the histories of these immigration events by studying the motions of individual stars throughout a galaxy and its extended halo of stars and dark matter. Such cosmic archaeology, however, has only been possible in our own galaxy, the Milky Way, until now.

An international team of researchers has uncovered striking new evidence of a large galactic immigration event in the Andromeda Galaxy, the Milky Way’s nearest large galactic neighbor. The new results were made with the DOE’s Dark Energy Spectroscopic Instrument (DESI) on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory, a Program of NSF’s NOIRLab.

By measuring the motions of nearly 7500 stars in the inner halo of the Andromeda Galaxy, also known as Messier 31 (M31), the team discovered telltale patterns in the positions and motions of stars that revealed how these stars began their lives as part of another galaxy that merged with M31 about 2 billion years ago. While such patterns have long been predicted by theory, they have never been seen with such clarity in any galaxy.

“Our new observations of the Milky Way’s nearest large galactic neighbor, the Andromeda Galaxy, reveal evidence of a galactic immigration event in exquisite detail,” explained Arjun Dey, astronomer at NSF’s NOIRLab and the lead author of the paper presenting this research. “Although the night sky may seem unchanging, the Universe is a dynamic place. Galaxies like M31 and our Milky Way are constructed from the building blocks of many smaller galaxies over cosmic history. “
“We have never before seen this so clearly in the motions of stars, nor had we seen some of the structures that result from this merger,” said Sergey Koposov, an astrophysicist at the University of Edinburgh and coauthor of the paper. “Our emerging picture is that the history of the Andromeda Galaxy is similar to that of our own Galaxy, the Milky Way. The inner halos of both galaxies are dominated by a single immigration event.”

Galactic Immigration in the Andromeda Galaxy.

This research sheds light on not only the history of our galactic neighbors but also the history of our own galaxy. Most of the stars in the Milky Way’s halo were formed in another galaxy and later migrated into our own in a galactic merger 8–10 billion years ago. Studying the relics of a similar, but more recent, galaxy merger in M31 gives astronomers a window onto one of the major events in the Milky Way’s past.

To trace the history of migration in M31, the team turned to DESI. DESI was constructed to map tens of millions of galaxies and quasars in the nearby Universe in order to measure the effect of dark energy on the expansion of the Universe. It is the most powerful multi-object survey spectrograph in the world, and is capable of measuring the spectra of more than 100,000 galaxies a night. DESI’s world-class capabilities can also be put to use closer to home, however, and the instrument was crucial to the team’s survey of M31.

“This science could not have been done at any other facility in the world. DESI’s amazing efficiency, throughput, and field of view make it the best system in the world to carry out a survey of the stars in the Andromeda Galaxy,” said Dey. “In only a few hours of observing time, DESI was able to surpass more than a decade of spectroscopy with much larger telescopes.”

Even though the Mayall Telescope was completed 50 years ago (it achieved first light in 1973), it remains a world-class astronomical facility thanks to continued upgrades and state-of-the-art instrumentation. “Fifty years sounds like a long time, and naïvely one might think that’s the natural lifetime of a facility,” said co-author Joan R. Najita, also at NOIRLab. “But with renewal and reuse, a venerable telescope like the Mayall can continue to make amazing discoveries despite being relatively small by today’s standards.”

The research was carried out in collaboration with two Harvard University undergraduates, Gabriel Maxemin and Joshua Josephy-Zack, who connected with the project through the Radcliffe Institute for Advanced Study. Najita was a Radcliffe Fellow from 2021 to 2022. The team now plans to use the unparalleled capabilities of DESI and the Mayall Telescope to explore more of M31’s outlying stars, with the aim of revealing its structure and immigration history in unprecedented detail.

“It’s amazing that we can look out at the sky and read billions of years of another galaxy’s history as written in the motions of its stars — each star tells part of the story,” concluded Najita. “Our initial observations exceeded our wildest expectations and we are now hoping to conduct a survey of the entire M31 halo with DESI. Who knows what new discoveries await!”

Prolonged microgravity induces reversible and persistent changes on human cerebral connectivity

by Steven Jillings, Ekaterina Pechenkova, Elena Tomilovskaya, et al in Communications Biology

Scientists of the University of Antwerp and University of Liège have found how the human brain changes and adapts to weightlessness, after being in space for 6 months. Some of the changes turned out to be lasting — even after 8 months back on Earth. Raphaël Liégeois, soon to be the third Belgian in space, acknowledges the importance of the research, “to prepare the new generation of astronauts for longer missions.”

A child who learns not to drop a glass on the floor, or a tennis player predicting the course of an incoming ball to hit it accurately are examples of how the brain incorporates the physical laws of gravity to optimally function on Earth. Astronauts who go to space reside in a weightless environment, where the brain’s rules about gravity are no longer applicable. A new study on brain function in cosmonauts has revealed how the brain’s organization is changed after a six-month mission to the International Space Station (ISS), demonstrating the adaptation that is required to live in weightlessness.

The University of Antwerp has been leading this BRAIN-DTI scientific project through the European Space Agency. Magnetic resonance imaging (MRI) data were taken from 14 astronaut brains before and several times after their mission to space. Using a special MRI technique, the researchers collected the astronauts’ brain data in a resting condition, hence without having them engage in a specific task. This resting-state functional MRI technique enabled the researchers to investigate the brain’s default state and to find out whether this changes or not after long-duration spaceflight.

Connectivity of the posterior cingulate cortex with the rest of the brain is reduced after spaceflight.

In collaboration with the University of Liège, recent analyses of the brain’s activity at rest revealed how functional connectivity, a marker of how activity in some brain areas is correlated with the activity in others, changes in specific regions.

“We found that connectivity was altered after spaceflight in regions which support the integration of different types of information, rather than dealing with only one type each time, such as visual, auditory, or movement information’, say Steven Jillings and Floris Wuyts (University of Antwerp). “Moreover, we found that some of these altered communication patterns were retained throughout 8 months of being back on Earth. At the same time, some brain changes returned to the level of how the areas were functioning before the space mission.”

Both scenarios of changes are plausible: retained changes in brain communication may indicate a learning effect, while transient changes may indicate more acute adaptation to changed gravity levels.

“This dataset is so special as their participants themselves. Back in 2016, we were historically the first to show how spaceflight may affect brain function on a single cosmonaut. Some years later we are now in a unique position to investigate the brains of more astronauts, several times. Therefore, we are deciphering the potential of the human brain all the more in confidence,” says Dr. Athena Demertzi (GIGA Institute, University of Liège), co-supervisor of this this work.

Functional connectivity networks associated with the posterior cingulate cortex, thalamus, right angular gyrus, and bilateral insula.

“Understanding physiological and behavioral changes triggered by weightlessness is key to plan human space exploration. Therefore, mapping changes of brain function using neuroimaging techniques as done in this work is an important step to prepare the new generation of astronauts for longer missions,” comments Raphaël Liégeois, Doctor of Engineering Science (ULiège) with a Thesis in the field of Neuroscience, future ESA Astronaut.

The researchers are excited with the results, though they know it is only the first step in pursuing our understanding of brain communication changes after space travel. For example, we still need to investigate what the exact behavioural consequence is for these brain communication changes, we need to understand whether longer time spent in outer space might influence these observations, and whether brain characteristics may be helpful in selecting future astronauts or monitoring them during and after space travel.

Quantification of Carbonates, Oxychlorines, and Chlorine Generated by Heterogeneous Electrochemistry Induced by Martian Dust Activity

by Alian Wang, Andrew W. Jackson, Neil C. Sturchio, Jen Houghton, Chuck Y. C. Yan, Kevin S. Olsen, Quincy H. K. Qu in Geophysical Research Letters

Mars is infamous for its intense dust storms, some of which kick up enough dust to be seen by telescopes on Earth.

When dust particles rub against each other, as they do in Martian dust storms, they can become electrified, transferring positive and negative electric charge in the same way as you build up static electricity if you shuffle across a carpet. Strong electric fields build up in dust storms on Earth, so it is perhaps unsurprising that this also happens on Mars. But what happens next? Probably not a sudden flash of lightning, as we might expect on Earth. Instead, planetary scientist Alian Wang at Washington University in St. Louis thinks electrical discharge on Mars probably looks more like a faint glow. (None of the Mars landers, rovers or other missions have captured a real picture of it.)

“It could be somewhat like the aurora in polar regions on Earth, where energetic electrons collide with dilute atmospheric species,” said Wang, a research professor of earth and planetary sciences in Arts & Sciences.

Flashy or not, this Martian “faux-rora” still packs a hefty punch. Wang’s new study shows that electricity in dust storms could be the major driving force of the Martian chlorine cycle. As background, scientists consider chlorine one of five elements that are “mobile” on Mars (the others are hydrogen, oxygen, carbon and sulfur). This means chlorine, in different forms, moves back and forth between the surface and the atmosphere on Mars. On the ground, chloride deposits — which are similar to saline playas or shallow salt flats on Earth — are widespread. These chloride deposits likely formed in the early history of Mars as precipitated chloride salts from brine.

Products from ESD_on_KCl (or MgCl2) in a Mars reaction chamber.

In the new study, Wang shows that one particularly efficient way to move chlorine from the ground to the air on Mars is by way of reactions set off by electrical discharge generated in Martian dust activities. Wang and her collaborators conducted a series of experiments that obtained high yields of chlorine gasses from common chlorides — all by zapping the solid salts with electrical discharge under Mars-like conditions. They conducted these experiments using a planetary simulation chamber at Washington University (called the Planetary Environment and Analysis Chamber, or PEACh).

“The high-releasing rate of chlorine from common chlorides revealed by this study indicates a promising pathway to convert surface chlorides to the gas phases that we now see in the atmosphere,” said Kevin Olsen, a research fellow at The Open University, in the United Kingdom, and a co-author of the new study.
“These findings offer support that Martian dust activities can drive a global chlorine cycle. With the ExoMars Trace Gas Orbiter, we see repeated seasonal activity that coincides with global and regional dust storms,” he said.

Raman and MIR spectra of initial chloride, electrostatic discharge (ESD) products, and standards.

“Frictional electrification is a common process in our solar system, with Martian dust activities known to be a powerful source of electrical charge buildup,” said Wang, who is a faculty fellow of the university’s McDonnell Center for the Space Sciences. “The thin atmosphere on Mars makes it much easier for accumulated electrical fields to break down in the form of electrostatic discharge. In fact, it’s a hundred times easier on Mars than on Earth.”

Scientists involved in the Viking missions that landed on Mars in the 1970s first proposed that dust storms might be a source of the new reactive chemistry on the red planet. However, the chemical effects of dust activities were difficult to study. Certain mission opportunities, like the ExoMars Schiaparelli EDM launched in 2016, ended in failure. Scientists turned to models and experimental studies.

In recent years, Wang and other scientists published research that shows that when electrostatic discharge interacts with chlorine salts in a Mars-like carbon dioxide-rich environment, it can generate perchlorates and carbonates, and also release chlorine as a gas. But this new study is the first to try to quantify just how much of these chemical products are actually produced during dust storm events.

“The reaction rates are huge,” Wang said. “Importantly, the released chlorine in a short-time mid-strength electrostatic discharge process is at a percent level.” This means that during a seven-hour simulated electrostatic discharge experiment, at least one out of every 100 chloride molecules is decomposed and then releases its chlorine atom into the atmosphere.

Similar but slightly lower, the formation rates of carbonates and perchlorates are at sub-percent and per-thousand levels, Wang said. These high yields lead Wang and her team to believe that Martian dust activities can be linked to three global phenomena recently revealed by Mars missions.

Electrical discharge can be tied to the extremely high concentrations of perchlorate and carbonate globally in Martian topsoil, she said. Quantitatively, the high end of the observed concentration ranges can be accumulated by dust storm-induced electrical discharge within less than half of the Amazonian period, the most recent period of Mars’ history, which is thought to have begun about 3 billion years ago. Also, the high yield of released chlorine atoms from chlorides can account for the high concentrations of hydrogen chloride observed in the Martian atmosphere during the 2018 and 2019 dust seasons, when assuming 1 to 10 cm thickness of Martian surface dust would be kicked up by a global dust storm.

“No other process that we know of can do this,” Wang said, “especially with such quantitatively high yield of chlorine release.”

Space Launch System acoustics: Far-field noise measurements of the Artemis-I launch

by Kent L. Gee, Grant W. Hart, Carson F. Cunningham, Mark C. Anderson, Michael S. Bassett, Logan T. Mathews, J. Taggart Durrant, Levi T. Moats, Whitney L. Coyle, Makayle S. Kellison, Margaret J. Kuffskie in JASA Express Letters

When the Artemis 1 mission was launched by NASA’s Space Launch System, SLS, in November, it became the world’s most powerful rocket, exceeding the thrust of the previous record holder, Saturn , by 13%. With liftoff came a loud roar heard miles away.

Researchers from Brigham Young University and Rollins College in Florida reported noise measurements during the launch at different locations around Kennedy Space Center. The data collected can be used to validate existing noise prediction models, which are needed to protect equipment as well as the surrounding environment and community. These data will be useful as more powerful lift vehicles, including the SLS series, are developed.

“We hope these early results will help prevent the spread of possible misinformation, as happened with the Saturn 5,” author Kent Gee said. “Numerous websites and discussion forums suggested sound levels that were far too high, with inaccurate reports of the Saturn 5’s sound waves melting concrete and causing grass fires.”

The combination of nighttime darkness, humidity, and backlighting provided a rare opportunity to view propagating pressure waves. Artemis 1 was launched with four liquid hydrogen-oxygen engines plus two solid-fuel rocket boosters (SRBs). According to the authors, the SRBs are likely the dominant noise source during liftoff. The investigators studied recordings at microphones located 1.5 km to 5.2 km from the launch pad. All stations were outside the blast danger area. Maximum noise levels at all five stations exceeded those predicted in a preliminary assessment. At 1.5 km from the pad, the maximum noise level reached 136 decibels. At a 5.2 km distance, the noise was 129 decibels, nearly 20 decibels higher than predicted by a prelaunch noise model.

Liftoff of the Artemis I mission from Kennedy Space Center.

“This suggests a need to revisit and probably revise those models,” author Grant Hart said.

A procedure known as A-weighting is often used to assess the impact of noise on humans. Because we don’t hear as well in some frequency ranges as others, a filter is applied to emphasize the sounds we do hear. Using this method, the investigators found noise levels at 5.2 km from the launchpad were about as loud as a chainsaw. A characteristic feature of rocket launches is a crackling sound from shock waves. These shocks represent instantaneous sound pressure increases that are much louder than crackling noises encountered in everyday life.

Author Whitney Coyle said, “We found the Artemis 1 noise level at 5 km had a crackling quality about 40 million times greater than a bowl of Rice Krispies.”
“Although this study is an important step forward, we still have a long way to go to understand everything about the generation, propagation, and perception of rocket noise,” Gee said.