TL;DR
- The largest, most advanced rover NASA has sent to another world touched down on Mars last Thursday, after a 203-day journey traversing 293 million miles (472 million kilometers). About the size of a car, the robotic geologist and astrobiologist will undergo several weeks of testing before it begins its two-year science investigation of Mars’ Jezero Crater. A fundamental part of its mission is astrobiology, including the search for signs of ancient microbial life.
- A scientist examined 11 Mars years of image data to understand the seasonal processes that create linear gullies on the slopes of the megadune in the Russell crater on Mars.
- A research team has succeeded in creating a micrometer-sized space-time crystal consisting of magnons at room temperature. With the help of a scanning transmission X-ray microscope, they were able to film the recurring periodic magnetization structure in a crystal.
- Astronomers have tested a method for reconstructing the state of the early Universe by applying it to 4000 simulated universes using the ATERUI II supercomputer. They found that together with new observations the method can set better constraints on inflation, one of the most enigmatic events in the history of the Universe. The method can shorten the observation time required to distinguish between various inflation theories.
- According to a new study, Earth, Venus and Mars were created from small dust particles containing ice and carbon. The discovery opens up the possibility that the Milky Way may be filled with aquatic planets.
- Astronomers have discovered that large galaxies are stealing the material that their smaller counterparts need to form new stars.
- A doctoral student has mined the most recent Gaia survey for all binary stars near Earth and created a 3D atlas of 1.3 million of them. The last local survey included about 200 binary pairs. With such census data, astronomers can conduct statistical analyses on binary populations. For pairs that contain white dwarfs, it’s possible to determine the age of their main-sequence companion, and thus of any exoplanets around them.
- SpaceX blames failed Falcon 9 booster landing on heat damage.
- NASA sees “reasonable chance” of the first SLS launch this year.
- DARPA orders six satellites from Blue Canyon Technologies for the Blackjack program.
- Starliner test flight slips to early April.
- Upcoming industry events. And more!
Space industry in numbers
Last summer, the Space Foundation published the second-quarter findings of its 2019 issue of The Space Report, revealing that:
- The global space economy grew 8.1% in 2018 to USA 414.75 billion, exceeding USD 400 billion for the first time.
- Global launches in 2018 increased by 46% over the number of launches a decade ago.
- Global launches in 2018 exceeded 100 for the first time since 1990.
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
NASA releases video of Perseverance landing:
NASA postpones second SLS Green Run test
NASA sees “reasonable chance” of first SLS launch this year
SpaceX blames failed Falcon 9 booster landing on heat damage
White House not making near-term plans to nominate a NASA administrator
DARPA orders six satellites from Blue Canyon Technologies for Blackjack program
SpaceX raises $850 million in latest round
DoD focus on climate could shape future investments in weather satellites
U.S. to support international effort to set rules of behavior in space
Inmarsat hires Nokia executive as new CEO
ClimaCell to launch dozens of radar satellites to improve forecasts
China launches trio of Yaogan-31 ocean reconnaissance satellites
EchoStar reports Jupiter-3 delay and nanosatellite failures
Lawmakers call for open dialogue on Chinese, Russian advances in space and nuclear weapons
Space Force awards engineering contract for certification of ULA’s Vulcan rocket
Former Capella Space and Planet executive joins Hydrosat
Orbit Fab and Benchmark Space Systems to partner on in-space refueling technologies
Redwire acquires Deployable Space Systems
L3Harris gets $137 million contract for GPS digital payloads
India revises Gaganyaan human spaceflight plan, delays Chandrayaan-3
Toast-shaped ThinSats attract educational and government customers
Pentagon chief Austin stands behind Air Force amid probe of Space Command basing decision
To defend the high frontier, Space Force wants digitally minded troops
General Atomics selects Firefly to launch NASA Earth science instrument
Safety panel recommends NASA develops strategy for workforce and infrastructure
Northrop Grumman launches Cygnus cargo spacecraft to space station
Pentagon inspector general to probe decision to move U.S. Space Command to Alabama
NOAA expands purchase of commercial radio occultation data for weather models
Landspace closes in on orbital launch with liquid methane rocket
Quebec invests in Telesat Lightspeed constellation
U.S. Space Command to recommend investments in space infrastructure
Space exploration
Real-Space Observation of Magnon Interaction with Driven Space-Time Crystals
by Nick Träger, Paweł Gruszecki, Filip Lisiecki, Felix Groß, Johannes Förster, Markus Weigand, Hubert Głowiński, Piotr Kuświk, Janusz Dubowik, Gisela Schütz, Maciej Krawczyk, Joachim Gräfe in Physical Review Letters
A German-Polish research team has succeeded in creating a micrometer-sized space-time crystal consisting of magnons at room temperature. With the help of the scanning transmission X-ray microscope Maxymus at Bessy II at Helmholtz Zentrum Berlin, they were able to film the recurring periodic magnetization structure in a crystal. Published in the Physical Review Letters, the research project was a collaboration between scientists from the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, the Adam Mickiewicz University and the Polish Academy of Sciences in Poznan in Poland.
Order in space and a periodicity in time
A crystal is a solid whose atoms or molecules are regularly arranged in a particular structure. If one looks at the arrangement with a microscope, one discovers an atom or a molecule always at the same intervals. It is similar with space-time crystals: however, the recurring structure exists not only in space, but also in time. The smallest components are constantly in motion until, after a certain period, they arrange again into the original pattern.
In 2012, the Nobel Prize winner in physics Frank Wilczek discovered the symmetry of matter in time. He is considered the discoverer of these so-called time crystals, although as a theorist he predicted them only hypothetically. Since then, several scientists have searched for materials in which the phenomenon is observed. The fact that space-time crystals actually exist was first confirmed in 2017. However, the structures were only a few nanometers in size and formed only at very cold temperatures below minus 250 degrees Celsius. The fact that the German-Polish scientists have now succeeded in imaging relatively large space-time crystals of a few micrometers in a video at room temperature is therefore considered groundbreaking. But also because they were able to show that their space-time crystal, which consists of magnons, can interact with other magnons that encounter it.
An exceptional experiment succeeded
“We took the regularly recurring pattern of magnons in space and time, sent more magnons in, and they eventually scattered. Thus, we were able to show that the time crystal can interact with other quasiparticles. No one has yet been able to show this directly in an experiment, let alone in a video,” says Nick Träger, a doctoral student at Max Planck Institute for Intelligent Systems who, together with Pawel Gruszecki, is first author of the publication.
In their experiment, Gruszecki and Träger placed a strip of magnetic material on a microscopic antenna through which they sent a radio-frequency current. This microwave field triggered an oscillating magnetic field, a source of energy that stimulated the magnons in the strip — the quasiparticle of a spin wave. Magnetic waves migrated into the strip from left and right, spontaneously condensing into a recurring pattern in space and time. Unlike trivial standing waves, this pattern was formed before the two converging waves could even meet and interfere. The pattern, which regularly disappears and reappears on its own, must therefore be a quantum effect.
Gisela Schütz, Director at Max Planck Institute for Intelligent Systems who heads the Modern Magnetic Systems Department, points out the uniqueness of the X-ray camera: “Not only can it make the wavefronts visible with very high resolution, which is 20 times better than the best light microscope. It can even do so at up to 40 billion frames per second and with extremely high sensitivity to magnetic phenomena as well.”
“We were able to show that such space-time crystals are much more robust and widespread than first thought,” says Pawel Gruszecki, a scientist at the Faculty of Physics of the Adam Mickiewicz University in Poznan. “Our crystal condenses at room temperature and particles can interact with it — unlike in an isolated system. Moreover, it has reached a size that could be used to do something with this magnonic space-time crystal. This may result in many potential applications.”
Joachim Gräfe, former research group leader in the Department of Modern Magnetic Systems and last author of the publication, concludes: “Classical crystals have a very broad field of applications. Now, if crystals can interact not only in space but also in time, we add another dimension of possible applications. The potential for communication, radar or imaging technology is huge.”
(a) Sketch of the sample with one magnonic Py stripe (yellow) and a coplanar waveguide (gray). (b) Snapshot of a time-resolved STXM movie. The gray scale represents the mz component. © Phase and amplitude map at fcw after FFT in time through each pixel of the STXM movie. The color code shows the amplitude and phase information.
A pebble accretion model for the formation of the terrestrial planets in the Solar System
by Anders Johansen, Thomas Ronnet, Martin Bizzarro, Martin Schiller, Michiel Lambrechts, Åke Nordlund, Helmut Lammer in Science Advances
Astronomers have long been looking into the vast universe in hopes of discovering alien civilisations. But for a planet to have life, liquid water must be present. The chances of that finding scenario have seemed impossible to calculate because it has been the assumption that planets like Earth get their water by chance if a large, ice asteroid hits the planet.
Now, researchers from the GLOBE Institute at the University of Copenhagen have published an eye-opening study, indicating that water may be present during the very formation of a planet. According to the study’s calculations, this is true for both Earth, Venus and Mars.
“All our data suggest that water was part of Earth’s building blocks, right from the beginning. And because the water molecule is frequently occurring, there is a reasonable probability that it applies to all planets in the Milky Way. The decisive point for whether liquid water is present is the distance of the planet from its star,” says Professor Anders Johansen from the Centre for Star and Planet Formation.
Using a computer model, Anders Johansen and his team have calculated how quickly planets are formed, and from which building blocks. The study indicates that it was millimetre-sized dust particles of ice and carbon — which are known to orbit around all young stars in the Milky Way — that 4.5 billion years ago accreted in the formation of what would later become Earth.
“Up to the point where Earth had grown to one percent of its current mass, our planet grew by capturing masses of pebbles filled with ice and carbon. Earth then grew faster and faster until, after five million years, it became as large as we know it today. Along the way, the temperature on the surface rose sharply, causing the ice in the pebbles to evaporate on the way down to the surface so that, today, only 0.1 percent of the planet is made up of water, even though 70 percent of Earth’s surface is covered by water,” says Anders Johansen, who together with his research team in Lund ten years ago put forward the theory that the new study now confirms.
The theory, called ‘pebble accretion’, is that planets are formed by pebbles that are clumping together, and that the planets then grow larger and larger.
Anders Johansen explains that the water molecule H2O is found everywhere in our galaxy, and that the theory therefore opens up the possibility that other planets may have been formed in the same way as Earth, Mars and Venus.
“All planets in the Milky Way may be formed by the same building blocks, meaning that planets with the same amount of water and carbon as Earth — and thus potential places where life may be present — occur frequently around other stars in our galaxy, provided the temperature is right,” he says.
If planets in our galaxy had the same building blocks and the same temperature conditions as Earth, there will also be good chances that they may have about the same amount of water and continents as our planet.
Professor Martin Bizzarro, co-author of the study, says: “With our model, all planets get the same amount of water, and this suggests that other planets may have not just the same amount of water and oceans, but also the same amount of continents as here on Earth. It provides good opportunities for the emergence of life.”
If, on the other hand, it was random how much water was present on planets, the planets might look vastly different. Some planets would be too dry to develop life, while others would be completely covered by water.
“A planet covered by water would of course be good for maritime beings, but would offer less than ideal conditions for the formation of civilisations that can observe the universe,” says Anders Johansen.
Anders Johansen and his research team are looking forward to the next generation of space telescopes, which will offer far better opportunities to observe exoplanets orbiting a star other than the Sun.
“The new telescopes are powerful. They use spectroscopy, which means that by observing which type of light is being blocked from the planets’ orbit around their star, you can see how much water vapour there is. It can tell us something about the number of oceans on that planet,” he says.
Sketch of the physical processes involved in our pebble accretion model for the formation of terrestrial planets.
Stage (A): The protoplanetary disc is formed consisting of material with solar composition (blue), represented in the meteoric record by the CI meteorites. Thermal processing in the inner disc vaporizes presolar grains carrying isotopic anomalies. The remaining solids carry now a noncarbonaceous (NC) signature (red). In stage (B), the disc expands outward due to angular momentum transport from the inner to the outer disc, carrying the NC material along with the gas. Planetesimal belts form at the water ice line (red) and by pileups of pebbles in the outer regions of the protoplanetary disc (blue); this outer planetesimal belt is envisioned here as the birth region of the giant planets. In stage (C ), protoplanets representing Earth, Venus, and Theia migrate out of the inner planetesimal belt. In the outer Solar System, Jupiter, Saturn, Uranus, and Neptune grow by pebble accretion and gas accretion. In stage (D). the CI material has drifted past the terrestrial planet zone, and the terrestrial planets shift their compositions more toward the CI meteorites. The CC form outside the orbits of Jupiter and Saturn. Last, in stage (E), the protoplanetary disc clears, and the planetesimals of NC and CC composition are scattered into the asteroid belt.
Airborne Dust Plumes Lofted by Dislodged Ice Blocks at Russell Crater, Mars
by Cynthia L. Dinwiddie, Timothy N. Titus in Geophysical Research Letters
A Southwest Research Institute (SwRI) scientist examined 11 Mars years of image data to understand the seasonal processes that create linear gullies on the slopes of the megadune in the Russell crater on Mars. In early spring images, captured by two different cameras on the Mars Reconnaissance Orbiter, SwRI’s Dr. Cynthia Dinwiddie noticed airborne plumes of dusty material associated with the linear dune gullies on the sand dune’s downwind slope. These clues point to active processes involving chunks of frozen CO2, or dry ice, sliding down the sand dune, kicking up sand and dust along the way.
Russell crater, on Mars, is home to the largest known sand dune in the solar system, providing a frequently imaged locale to study modern surface activity on the Red Planet.
“For two decades, planetary scientists have had many ideas about how and when very long, narrow gullies formed on frost-affected sand dunes on Mars,” said Dinwiddie, first author of a paper outlining new research. “Initially, scientists thought linear dune gullies were remnants of an ancient time when the climate on Mars supported liquid water on its surface. Then, repeat imaging showed that changes were happening now, when Mars is cold and arid. Several hypotheses have since been proposed, usually involving either CO2 ice or water ice.”
Other scientists found imagery showing bright CO2 ice blocks at rest in dune gullies, suggesting a causal relationship between the blocks and the gullies.
“In this paper, we offer compelling new evidence that venting CO2 gas dislodges CO2 ice blocks that carve and modify linear dune gullies,” Dinwiddie said. “While trace amounts of seasonally condensed water are present, it behaves like an innocent bystander, not actively participating in the processes,” said coinvestigator Dr. Tim Titus of the U.S. Geological Survey.
During the bleak Martian fall and winter, cold temperatures condense part of the CO2 atmosphere onto the dune field’s surface, creating ice deposits. Previous research has shown that in the winter and early spring, the translucent slab of CO2 ice allows radiation from the Sun to heat the dark sand under the ice, causing some ice to transition to gas (or sublimate) and become pressurized in the contact zone. This pressurized CO2 gas escapes to the atmosphere via weak zones in the ice, also expelling sand and dust in a jet of gas.
The ejected material falls back to the surface and forms dark spots around the vent. This research proposes that as the season wears on, repetitive venting breaks up the slab ice into discrete blocks on steep slopes near the crest of the dune. Venting gas eventually dislodges the blocks, and sends them sliding downslope, deepening and modifying existing gullies or carving new ones.
The airborne plumes consist of fine dust disturbed by the sliding block, whereas coarse dust is redeposited near the gullies, creating a seasonal, relatively bright fringe around active gullies. The off-gassing ice blocks temporarily clean dust from the dark gully sand, resulting in telltale brightness (albedo) variations in and around gullies.
“We observe this bright fringe pattern around active gullies for a short period of time, say, the equivalent of the last three weeks of October, which is early to mid-spring in the Earth’s southern hemisphere,” Dinwiddie said. “Shortly after this ‘spring break,’ Mars’ dusty atmosphere blankets the area with a more homogenous façade, disturbed only by dust devils in the late spring and summer.”
SwRI led this program, with thermal modeling of ice and dust provided by Titus and the U.S. Geological Survey. A NASA Mars Data Analysis Program grant funded this 12-month pilot study of seasonal dune processes in Russell crater. Dinwiddie and Titus have proposed to extend this research to other craters in the southern hemisphere of Mars, where craters provide low-lying traps for sand to accumulate and form frost-affected dune fields.
A million binaries from Gaia eDR3: sample selection and validation of Gaia parallax uncertainties
by Kareem El-Badry, Hans-Walter Rix, Tyler M Heintz in Monthly Notices of the Royal Astronomical Society
&
TOI-1259Ab — a gas giant planet with 2.7% deep transits and a bound white dwarf companion
by David V. Martin, Kareem El-Badry, Vedad Kunovac Hodžić, Amaury H. M. J. Triaud, Ruth Angus, Jessica Birky, Daniel Foreman-Mackey, Christina Hedges, Benjamin T. Montet, Simon J. Murphy, Alexandre Santerne, Keivan G. Stassun et al. in arXiv,
The latest star data from the Gaia space observatory has for the first time allowed astronomers to generate a massive 3D atlas of widely separated binary stars within about 3,000 light years of Earth — 1.3 million of them.
The one-of-a-kind atlas, created by Kareem El-Badry, an astrophysics Ph.D. student from the University of California, Berkeley, should be a boon for those who study binary stars — which make up at least half of all sunlike stars — and white dwarfs, exoplanets and stellar evolution, in general. Before Gaia, the last compilation of nearby binary stars, assembled using data from the now-defunct Hipparcos satellite, included about 200 likely pairs.
“This is just a massive increase in sample size,” said El-Badry. “And it is an increase in what kinds of evolutionary phases we find the binaries in. In our sample, we have 17,000 white dwarfs alone. This is a much bigger census.”
White dwarfs are the end stages of most stars; the sun will likely end up as a compact white dwarf in 5 billion years. El-Badry’s atlas includes 1,400 systems that consist of two white dwarfs and 16,000 binaries that consist of a white dwarf and another type of star
The vast majority of the 2.6 million individual stars are still in the prime of life, however. Astronomers refer to them as main sequence stars, because they cluster along a line when plotted on a graph showing temperature versus brightness.
With such a large sample size, El-Badry said, it’s possible to do population demographics of these stellar twins, asking questions such as: What is the distribution of mass ratios of the two stars in all these binary systems? How are their separations or eccentricities distributed?
El-Badry plans to focus in the future on the white dwarf binaries, because white dwarfs can be assigned an age more precisely than is possible with regular stars. Main sequence stars like the sun can look the same for billions, or even tens of billions, of years, while white dwarfs change — for one thing, they cool down at a well-defined rate. And since binary pairs are birthed at the same time, the age of the white dwarf tells astronomers the age of its main-sequence twin, or of any planets around the stars.
“For a white dwarf, in general, it is easy to tell how old it is — not just how old since it became a white dwarf, but what its total age is,” he said. “You can also measure their masses, because white dwarfs have a well-understood mass-radius relation.”
As an example, El-Badry and colleagues recently used the Gaia data to estimate the age of a Jupiter-sized gas giant discovered by the TESS satellite around a white dwarf-K dwarf pair. That exoplanet, TOI-1259Ab, turned out to be about 4 billion years old, based on the age of the white dwarf.
“In this catalog, there are something like 15 systems like this: star plus planet plus white dwarf,” he said, “and there are another few hundred that are star plus planet plus another star. Those are also potentially interesting because, in some cases, the other star will do something dynamically to the planet.”
El-Badry also collaborated with Jackie Faherity, a scientist and educator at the American Museum of Natural History in New York City, to create a video fly-through of all the million binary stars around Earth, which represents a good chunk of the entire Milky Way Galaxy.
Binary stars
Until Gaia was launched by the European Space Agency in 2013 to precisely measure the distances and motions of millions of nearby stars, the only way to find binaries was to look for stars close together in the sky. This can be tricky, because stars that look very close from Earth could be hundreds to thousands of light-years from one another, merely sitting along the same line of site.
Ruling out a chance alignment requires lots of observing time to confirm that the two candidates are actually at the same distance and moving together. Because of Earth’s motion around the sun, nearby stars appear to change position in the sky, and that parallax can be used to calculate how far away they are. The star’s motion across the sky, known as proper motion, helps determine its velocity.
Gaia conducts this tedious astrometry continuously for all nearby stars in the sky, 24/7, from its orbit at the Earth-Sun Lagrange point. The space telescope’s survey is most useful for stars within about 3,000 light years of Earth, however, because beyond that, the parallax is usually too small to measure.
El-Badry first looked for binary stars in Gaia data after the mission’s second release of star measurements in 2018, with the help of colleagues Hans-Walter Rix, director of the Max-Planck Institute for Astronomy in Heidelberg, Germany, and Tyler Heintz, a graduate student at Boston University. They developed computational techniques to identify stars moving together through space and at the same distance from Earth. The technique basically projects each star’s movement over thousands of years, based on its proper motion today, and pulls out stars that are moving in the same direction. If they also turn out to be at the same distance based on parallax, they’re probably bound to one another, he said.
He and his colleagues focus primarily on wide-binaries — those separated by a distance of 10 AU (astronomical units) or more — that is, 10 or more times the distance between Earth and the sun (93 million miles). Stars closer than that typically appear as one point of light and require other spectroscopic techniques to distinguish whether they are true binaries.
To get first crack at Gaia’s latest data, El-Badry arose at 3 a.m. on the release date, Dec. 3 of last year, and joined some 100 other astronomers from around the world on Zoom. He quickly ran pre-programmed queries on the data to extract the catalog information he needed to create the 3D map.
The initial queries returned some 1.8 million binary candidates from Gaia’s catalog of 1.8 billion stars, so El-Badry first had to assess the likelihood that some of the pairs were at the same distance and moving in similar directions just by chance, not because they are paired. He estimates that nearly 1.3 million pairs had at least a 90% chance of being bound, and 1.1 million had a 99% chance.
“About half of all sun-like stars are binaries, many of them too close to distinguish, but we find something like 25% of all sun-like stars have a binary companion at separations of more than 30 AU, about the distance to Pluto,” he said. “The distribution peaks at a separation of 30 or 50 AU.”
Some pairs are separated by as much as a parsec — 260,000 AU, or 3.26 light years — though most are within 1,000 AU of one another.
One takeaway, he said, is that the new analysis confirms something hinted at in the 2018 data: Many binary star pairs are very similar in mass.
“One thing we already found that is cool — we discovered this with Gaia DR2, but now we can study it better with this sample — is that binaries like to be identical twins,” he said. “That is really weird, because most of these are separated by hundreds or thousands of AU, so they are so far apart that, by conventional star formation theories, their masses should be random. But the data tells a different story: They know something about their companions’ masses.”
Constraining primordial non-Gaussianity with postreconstructed galaxy bispectrum in redshift space
by Masato Shirasaki, Naonori S. Sugiyama, Ryuichi Takahashi, Francisco-Shu Kitaura in Physical Review D
Astronomers have tested a method for reconstructing the state of the early Universe by applying it to 4000 simulated universes using the ATERUI II supercomputer at the National Astronomical Observatory of Japan (NAOJ). They found that together with new observations the method can set better constraints on inflation, one of the most enigmatic events in the history of the Universe. The method can shorten the observation time required to distinguish between various inflation theories.
Just after the Universe came into existence 13.8 billion years ago, it suddenly increased more than a trillion, trillion times in size, in less than a trillionth of a trillionth of a microsecond; but no one knows how or why. This sudden “inflation,” is one of the most important mysteries in modern astronomy. Inflation should have created primordial density fluctuations which would have affected the distribution of where galaxies developed. Thus, mapping the distribution of galaxies can rule out models for inflation which don’t match the observed data.
However, processes other than inflation also impact galaxy distribution, making it difficult to derive information about inflation directly from observations of the large-scale structure of the Universe, the cosmic web comprised of countless galaxies. In particular, the gravitationally driven growth of groups of galaxies can obscure the primordial density fluctuations.
A research team led by Masato Shirasaki, an assistant professor at NAOJ and the Institute of Statistical Mathematics, thought to apply a “reconstruction method” to turn back the clock and remove the gravitational effects from the large-scale structure. They used ATERUI II, the world’s fastest supercomputer dedicated to astronomy simulations, to create 4000 simulated universes and evolve them through gravitationally driven growth. They then applied this method to see how well it reconstructed the starting state of the simulations. The team found that their method can correct for the gravitational effects and improve the constraints on primordial density fluctuations.
“We found that this method is very effective,” says Shirasaki. “Using this method, we can verify of the inflation theories with roughly one tenth the amount of data. This method can shorten the required observing time in upcoming galaxy survey missions such as SuMIRe by NAOJ’s Subaru Telescope.”
Molecular hydrogen in IllustrisTNG galaxies: carefully comparing signatures of environment with local CO and SFR data
by Adam R H Stevens, Claudia del P Lagos, Luca Cortese, Barbara Catinella, Benedikt Diemer, Dylan Nelson, Annalisa Pillepich, Lars Hernquist, Federico Marinacci, Mark Vogelsberger in Monthly Notices of the Royal Astronomical Society
Large galaxies are known to strip the gas that occupies the space between the stars of smaller satellite galaxies.
In research published last week, astronomers have discovered that these small satellite galaxies also contain less ‘molecular’ gas at their centres.
Molecular gas is found in giant clouds in the centres of galaxies and is the building material for new stars. Large galaxies are therefore stealing the material that their smaller counterparts need to form new stars.
Lead author Dr Adam Stevens is an astrophysicist based at UWA working for the International Centre for Radio Astronomy Research (ICRAR) and affiliated to the ARC Centre of Excellence in All Sky Astrophysics in 3 Dimensions (ASTRO 3D).
Dr Stevens said the study provides new systematic evidence that small galaxies everywhere lose some of their molecular gas when they get close to a larger galaxy and its surrounding hot gas halo.
“Gas is the lifeblood of a galaxy,” he said. “Continuing to acquire gas is how galaxies grow and form stars. Without it, galaxies stagnate. We’ve known for a long time that big galaxies strip ‘atomic’ gas from the outskirts of small galaxies. But, until now, it hadn’t been tested with molecular gas in the same detail.”
ICRAR-UWA astronomer Associate Professor Barbara Catinella said galaxies don’t typically live in isolation.
“Most galaxies have friends,” she says. “And when a galaxy moves through the hot intergalactic medium or galaxy halo, some of the cold gas in the galaxy is stripped away. This fast-acting process is known as ram pressure stripping.”
The research was a global collaboration involving scientists from the University of Maryland, Max Planck Institute for Astronomy, University of Heidelberg, Harvard-Smithsonian Center for Astrophysics, University of Bologna and Massachusetts Institute of Technology.
Molecular gas is very difficult to detect directly. The research team took a state-of-the-art cosmological simulation and made direct predictions for the amount of atomic and molecular gas that should be observed by specific surveys on the Arecibo telescope in Puerto Rico and the IRAM 30-meter telescope in Spain. They then took the actual observations from the telescopes and compared them to their original predictions. The two were remarkably close.
Associate Professor Catinella, who led the Arecibo survey of atomic gas, says the IRAM 30-meter telescope observed the molecular gas in more than 500 galaxies.
“These are the deepest observations and largest sample of atomic and molecular gas in the local Universe,” she says. “That’s why it was the best sample to do this analysis.”
The team’s finding fits with previous evidence that suggests satellite galaxies have lower star formation rates.
Dr Stevens said stripped gas initially goes into the space around the larger galaxy. “That may end up eventually raining down onto the bigger galaxy, or it might end up just staying out in its surroundings,” he said.
But in most cases, the little galaxy is doomed to merge with the larger one anyway.
“Often they only survive for one to two billion years and then they’ll end up merging with the central one,” Dr Stevens said. “So it affects how much gas they’ve got by the time they merge, which then will affect the evolution of the big system as well. Once galaxies get big enough, they start to rely on getting more matter from the cannibalism of smaller galaxies.”
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