Extraterrestrial chemistry with earthbound possibilities

Who are we? Why are we here? As the Crosby, Stills, Nash & Young song suggests, we are stardust, the result of chemistry occurring throughout vast clouds of interstellar gas and dust. To better understand how that chemistry could create prebiotic molecules -- the seeds of life on Earth and possibly elsewhere -- researchers investigated the role of low-energy electrons created as cosmic radiation traverses through ice particles. Their findings may also inform medical and environmental applications on our home planet.

Undergraduate student Kennedy Barnes will present the team's results at the fall meeting of the American Chemical Society (ACS).

"The first detection of molecules in space was made by Wellesley College alum Annie Jump Cannon more than a hundred years ago," says Barnes, who, with fellow undergraduate Rong Wu, led this study at Wellesley, mentored by chemistry professor Christopher Arumainayagam and physics professor James Battat. Since Cannon's discovery, scientists have been interested in finding out how extraterrestrial molecules form. "Our goal is to explore the relative importance of low-energy electrons versus photons in instigating the chemical reactions responsible for the extraterrestrial synthesis of these prebiotic molecules," Barnes explains.

The few studies that previously probed this question suggested that both electrons and photons can catalyze the same reactions. Studies by Barnes and colleagues, however, hint that the prebiotic molecule yield from low-energy electrons and photons could be significantly different in space. "Our calculations suggest that the number of cosmic-ray-induced electrons within cosmic ice could be much greater than the number of photons striking the ice," Barnes explains. "Therefore, electrons likely play a more significant role than photons in the extraterrestrial synthesis of prebiotic molecules."

Aside from cosmic ice, her research into low-energy electrons and radiation chemistry also has potential applications on Earth. Barnes and colleagues recently studied the radiolysis of water, finding evidence of electron-stimulated release of hydrogen peroxide and hydroperoxyl radicals, which destroy stratospheric ozone and act as damaging reactive oxygen species in cells.

"A lot of our water radiolysis research findings could be used in medical applications and medical simulations," Barnes shares, offering the example of using high-energy radiation to treat cancer. "I once had a biochemistry professor say that humans are basically bags of water. So, other scientists are investigating how low-energy electrons produced in water affect our DNA molecules."

She also says the team's findings are applicable to environmental remediation efforts where wastewater is being treated with high-energy radiation, which produces large numbers of low-energy electrons that are assumed to be responsible for the destruction of hazardous chemicals.

Back to space chemistry, in attempting to better understand prebiotic molecule synthesis, the researchers didn't limit their efforts to mathematical modeling; they also tested their hypothesis by mimicking the conditions of space in the lab. They use an ultrahigh-vacuum chamber containing an ultrapure copper substrate that they can cool to ultralow temperatures, along with an electron gun that produces low-energy electrons and a laser-driven plasma lamp that produces low-energy photons. The scientists then bombard nanoscale ice films with electrons or photons to see what molecules are produced.

"Although we have previously focused on how this research is applicable to interstellar submicron ice particles, it is also relevant to cosmic ice on a much larger scale, like that of Jupiter's moon Europa, which has a 20-mile-thick ice shell," says Barnes.

Thus, she suggests their research will help astronomers understand data from space exploration missions such as NASA's James Webb Space Telescope as well as the Europa Clipper, initially expected to launch in October 2024. Barnes hopes that their findings will inspire other researchers to incorporate low-energy electrons into their astrochemistry models that simulate what happens within cosmic ices.

Barnes and colleagues are also varying the molecular composition of ice films and exploring atom addition reactions to see if low-energy electrons can produce other prebiotic chemistries. This work is being performed in collaboration with researchers at the Laboratory for the Study of Radiation and Matter in Astrophysics and Atmospheres in France.

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How Saharan dust regulates hurricane rainfall

Giant plumes of Sahara Desert dust that gust across the Atlantic can suppress hurricane formation over the ocean and affect weather in North America.

But thick dust plumes can also lead to heavier rainfall -- and potentially more destruction -- from landfalling storms, according to a July 24 study in Science Advances. The research shows a previously unknown relationship between hurricane rainfall and Saharan dust plumes.

"Surprisingly, the leading factor controlling hurricane precipitation is not, as traditionally thought, sea surface temperature or humidity in the atmosphere. Instead, it's Sahara dust," said the corresponding author Yuan Wang, an assistant professor of Earth system science at the Stanford Doerr School of Sustainability.

Previous studies have found that Saharan dust transport may decline dramatically in the coming decades and hurricane rainfall will likely increase due to human-caused climate change.

However, uncertainty remains around the questions of how climate change will affect outflows of dust from the Sahara and how much more rainfall we should expect from future hurricanes. Additional questions surround the complex relationships among Saharan dust, ocean temperatures, and hurricane formation, intensity, and precipitation. Filling in the gaps will be critical to anticipating and mitigating the impacts of climate change.

"Hurricanes are among the most destructive weather phenomena on Earth," said Wang. Even relatively weak hurricanes can produce heavy rains and flooding hundreds of miles inland. "For conventional weather predictions, especially hurricane predictions, I don't think dust has received sufficient attention to this point."

Competing effects

Dust can have competing effects on tropical cyclones, which are classified as hurricanes in the North Atlantic, central North Pacific, and eastern North Pacific when maximum sustained wind speeds reach 74 miles per hour or higher.

"A dust particle can make ice clouds form more efficiently in the core of the hurricane, which can produce more precipitation," Wang explained, referring to this effect as microphysical enhancement. Dust can also block solar radiation and cool sea surface temperatures around a storm's core, which weakens the tropical cyclone.

Wang and colleagues set out to first develop a machine learning model capable of predicting hurricane rainfall, and then identify the underlying mathematical and physical relationships.

The researchers used 19 years of meteorological data and hourly satellite precipitation observations to predict rainfall from individual hurricanes.

The results show a key predictor of rainfall is dust optical depth, a measure of how much light filters through a dusty plume. They revealed a boomerang-shaped relationship in which rainfall increases with dust optical depths between 0.03 and 0.06, and sharply decreases thereafter. In other words, at high concentrations, dust shifts from boosting to suppressing rainfall.

"Normally, when dust loading is low, the microphysical enhancement effect is more pronounced. If dust loading is high, it can more efficiently shield [the ocean] surface from sunlight, and what we call the 'radiative suppression effect' will be dominant," Wang said.

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Beautiful nebula, violent history: Clash of stars solves stellar mystery

When astronomers looked at a stellar pair at the heart of a stunning cloud of gas and dust, they were in for a surprise. Star pairs are typically very similar, like twins, but in HD 148937, one star appears younger and, unlike the other, is magnetic. New data from the European Southern Observatory (ESO) suggest there were originally three stars in the system, until two of them clashed and merged. This violent event created the surrounding cloud and forever altered the system's fate.

"When doing background reading, I was struck by how special this system seemed," says Abigail Frost, an astronomer at ESO in Chile and lead author of the study published today in Science. The system, HD 148937, is located about 3800 light-years away from Earth in the direction of the Norma constellation.

It is made up of two stars much more massive than the Sun and surrounded by a beautiful nebula, a cloud of gas and dust.

"A nebula surrounding two massive stars is a rarity, and it really made us feel like something cool had to have happened in this system. When looking at the data, the coolness only increased."

"After a detailed analysis, we could determine that the more massive star appears much younger than its companion, which doesn't make any sense since they should have formed at the same time!" Frost says.

The age difference -- one star appears to be at least 1.5 million years younger than the other -- suggests something must have rejuvenated the more massive star.

Another piece of the puzzle is the nebula surrounding the stars, known as NGC 6164/6165.

It is 7500 years old, hundreds of times younger than both stars.

The nebula also shows very high amounts of nitrogen, carbon and oxygen.

This is surprising as these elements are normally expected deep inside a star, not outside; it is as if some violent event had set them free.

To unravel the mystery, the team assembled nine years' worth of data from the PIONIER and GRAVITY instruments, both on ESO's Very Large Telescope Interferometer (VLTI), located in Chile's Atacama Desert.

They also used archival data from the FEROS instrument at ESO's La Silla Observatory.

"We think this system had at least three stars originally; two of them had to be close together at one point in the orbit whilst another star was much more distant," explains Hugues Sana, a professor at KU Leuven in Belgium and the principal investigator of the observations.

"The two inner stars merged in a violent manner, creating a magnetic star and throwing out some material, which created the nebula. The more distant star formed a new orbit with the newly merged, now-magnetic star, creating the binary we see today at the centre of the nebula."

"The merger scenario was already in my head back in 2017 when I studied nebula observations obtained with the European Space Agency's Herschel Space Telescope," adds co-author Laurent Mahy, currently a senior researcher at the Royal Observatory of Belgium.

"Finding an age discrepancy between the stars suggests that this scenario is the most plausible one and it was only possible to show it with the new ESO data."

This scenario also explains why one of the stars in the system is magnetic and the other is not -- another peculiar feature of HD 148937 spotted in the VLTI data.

At the same time, it helps solve a long-standing mystery in astronomy: how massive stars get their magnetic fields.

While magnetic fields are a common feature of low-mass stars like our Sun, more massive stars cannot sustain magnetic fields in the same way.

Yet some massive stars are indeed magnetic.

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Astronomers conduct first search for forming planets with new space telescope

Planets form in disks of dust and gas called protoplanetary disks that whirl around a central protostar during its final assembly.

Although several dozens of such disks have been imaged, just two planets have been caught in the act of forming so far. Now, astronomers are aiming the powerful instruments aboard the James Webb Space Telescope at protoplanetary disks to try to find early clues about the ways in which planets form, and how these planets influence their natal disk.

A trio of studies led by the University of Michigan, University of Arizona and University of Victoria combined JWST's images with prior observations made by the Hubble Space Telescope and the Atacama Large Millimeter Array, or ALMA, in Chile. Based on the ancillary observations, the team used JWST to observe protoplanetary disks HL Tau, SAO 206462 and MWC 758 in hopes of detecting any planets that might be forming.

In the papers, published in The Astronomical Journal, the researchers pieced together previously unseen interactions between the planet-forming disk and the envelope of gas and dust surrounding the young stars at the center of the protoplanetary disks.

To catch a planet

The U-M study, led by U-M astronomer Gabriele Cugno, aimed JWST at a disk surrounding a protostar called SAO 206462. There, the researchers potentially found a planet candidate in the act of forming in a protoplanetary disk -- but it wasn't the planet they expected to find.

"Several simulations suggest that the planet should be within the disk, massive, large, hot, and bright. But we didn't find it. This means that either the planet is much colder than we think, or it may be obscured by some material that prevents us from seeing it," said Cugno, also a co-author on all three papers. "What we have found is a different planet candidate, but we cannot tell with 100% certainty whether it's a planet or a faint background star or galaxy contaminating our image. Future observations will help us understand exactly what we are looking at."

Astronomers have observed the disk in the past, notably with the Hubble Space Telescope, the Subaru Telescope, the Very Large Telescope and ALMA. These observations show a disk composed of two strong spirals, which are likely launched by a forming planet. The planet the U-M team expected to find is a type called a gas giant, planets composed mainly of hydrogen and helium, similar to Jupiter in our own solar system.

"The problem is, whatever we're trying to detect is hundreds of thousands, if not millions of times fainter than the star," Cugno said. "That's like trying to detect a little light bulb next to a lighthouse."

To peer more closely into the disk, the team used an instrument on JWST called NIRCam. NIRCam detects infrared light, and the astronomers used the instrument employing a technique called angular differential imaging. This technique can be used to detect both the thermal radiation of the planet, as the team has done to detect the planet candidate, and specific emission lines associated with material falling onto the planet and hitting its surface with high velocity.

"When material falls onto the planet, it shocks at the surface and gives off an emission line at specific wavelengths," Cugno said. "We use a set of narrow-band filters to try to detect this accretion. This has been done before from the ground at optical wavelengths, but this is the first time it's been done in the infrared with JWST."

Imaging the 'raw material' of planets

The University of Victoria paper, led by astronomy student Camryn Mullin, describes images of the disk surrounding the young star HL Tau.

"HL Tau is the youngest system in our survey, and still surrounded by a dense inflow of dust and gas falling onto the disk," said Mullin, a co-author of all three studies. "We were amazed by the level of detail with which we could see this surrounding material with JWST, but unfortunately, it obscures any signals from potential planets. "

HL Tau's disk is known for having several solar-system scale rings and gaps which could harbor planets.

"While there is a ton of evidence for ongoing planet formation, HL Tau is too young with too much intervening dust to see the planets directly," said Jarron Leisenring, the principal investigator of the observing campaign searching for forming planets and astronomer at the University of Arizona Steward Observatory. "We have already begun looking at other young systems with known planets to help form a more complete picture."

However, to the team's surprise, JWST revealed unexpected details of a different feature: the proto-stellar envelope, which is essentially a dense inflow of dust and gas surrounding the young star that is just beginning to coalesce, according to Leisenring. Under the influence of gravity, material from the interstellar medium falls inward onto the star and the disk, where it serves as the raw material for planets and their precursors.

The UArizona study, led by Kevin Wagner, a NASA Hubble/Sagan Fellow at UArizona Steward Observatory, examined the protoplanetary disk of MWC 758. Similar to SAO 206462, previous observations by the UArizona-led team revealed spiral arms forming in the disk, hinting at a massive planet orbiting its host star.

While no new planets were detected in the disk during the most recent observations, the sensitivity is groundbreaking, the researchers say, as it allows them to place the most stringent constraints yet on the suspected planets. For one, the results rule out the existence of additional planets in the outer regions of the MWC 758, consistent with a single giant planet driving the spiral arms.

"The lack of planets detected in all three systems tells us that the planets causing the gaps and spiral arms either are too close to their host stars or too faint to be seen with JWST," said Wagner, a co-author of all three studies. "If the latter is true, it tells us that they're of relatively low mass, low temperature, enshrouded in dust, or some combination of the three -- as is likely the case in MWC 758."

The search for forming planets continues

Catching planets in the act of forming is important because astronomers can glean information not only about the formation process, but how chemical elements get distributed throughout a planetary system.

"Only about 15 percent of stars like the sun have planets like Jupiter. It's really important to understand how they form and evolve, and to refine our theories," said U-M Michael Meyer, U-M astronomer and coauthor of all three studies. "Some astronomers think that these gas giant planets regulate the delivery of water to rocky planets forming in the inner parts of the disks."

Knowing how these disks are shaped by gas giants will help astronomers ultimately understand the properties and evolution of protoplanetary disks that later give rise to rocky, Earth-like planets, said Meyer.

"Basically in every disk we have observed with high enough resolution and sensitivity, we have seen large structures like gaps, rings and, in the case of SAO 206462, spirals," Cugno said. "Most if not all of these structures can be explained by forming planets interacting with the disk material, but other explanations that do not involve the presence of giant planets exist.

Read more at Science Daily

James Webb Space Telescope captures the end of planet formation

Scientists believe that planetary systems like our solar system contain more rocky objects than gas-rich ones. Around our sun, these include the inner planets -- Mercury, Venus, Earth and Mars -- the asteroid belt and the Kuiper belt objects such as Pluto.

Jupiter, Saturn, Uranus and Neptune, on the other hand, contain mostly gas. But scientists also have known for a long time that planet-forming disks start out with 100 times more mass in gas than solids, which leads to a pressing question: When and how does most of the gas leave a nascent planetary system?

A new study led by Naman Bajaj at the University of Arizona Lunar and Planetary Laboratory, published in the Astronomical Journal, provides answers. Using the James Webb Space Telescope, or JWST, the team obtained images from such a nascent planetary system -- also known as a circumstellar disk -- in the process of actively dispersing its gas into surrounding space.

"Knowing when the gas disperses is important as it gives us a better idea of how much time gaseous planets have to consume the gas from their surroundings," said Bajaj, a second-year doctoral student at UArizona's Lunar and Planetary Laboratory. "With unprecedented glimpses into these disks surrounding young stars, the birthplaces of planets, JWST helps us uncover how planets form."

During the very early stages of planetary system formation, planets coalesce in a spinning disk of gas and tiny dust around the young star, according to Bajaj. These particles clump together, building up into bigger and bigger chunks called planetesimals. Over time, these planetesimals collide and stick together, eventually forming planets. The type, size and location of planets that form depend on the amount of material available and how long it remains in the disk.

"So, in short, the outcome of planet formation depends on the evolution and dispersal of the disk," Bajaj said.

At the heart of this discovery is the observation of T Cha, a young star -- relative to the sun, which is about 4.6 billion years old -- enveloped by an eroding circumstellar disk notable for a vast dust gap, spanning approximately 30 astronomical units, or au, with one au being the average distance between the Earth and the sun.

Bajaj and his team were able, for the first time, to image the disk wind, as the gas is referred to when it slowly leaves the planet-forming disk. The astronomers took advantage of the telescope's sensitivity to light emitted by an atom when high-energy radiation -- for example, in starlight -- strips one or more electrons from its nucleus. This is known as ionization, and the light emitted in the process can be used as a sort of chemical "fingerprint" -- in the case of the T Cha system, tracing two noble gases, neon and argon. The observations also mark the first time a double ionization of argon has been detected in a planet-forming disk, the team writes in the paper.

"The neon signature in our images tells us that the disk wind is coming from an extended region away from the disk," Bajaj said. "These winds could be driven either by high-energy photons -- essentially the light streaming from the star -- or by the magnetic field that weaves through the planet-forming disk."

In an effort to differentiate between the two, the same group, this time led by Andrew Sellek, a postdoctoral researcher at Leiden University in the Netherlands, performed simulations of the dispersal driven by stellar photons, the intense light streaming from the young star. They compared these simulations to the actual observations and found dispersal by high-energy stellar photons can explain the observations, and hence cannot be excluded as a possibility. That study concluded that the amount of gas dispersing from the T Cha disk every year is equivalent to that of Earth's moon. These results will be published in a companion paper, currently under review with the Astronomical Journal.

While neon signatures had been detected in many other astronomical objects, they weren't known to originate in low-mass planet-forming disks until first discovered in 2007 with JWST's predecessor, NASA's Spitzer Space Telescope, by Ilaria Pascucci, a professor at LPL who soon identified them as a tracer of disk winds. Those early findings transformed research efforts focused on understanding gas dispersal from circumstellar disks. Pascucci is the principal investigator on the most recent observing project and a co-author on the publications reported here.

"Our discovery of spatially resolved neon emission -- and the first detection of double ionized argon -- using the James Webb Space Telescope could become the next step towards transforming our understanding of how gas clears out of a planet-forming disk," Pascucci said. "These insights will help us get a better idea of the history and impact on our own solar system."

In addition, the group has also discovered that the inner disk of T Cha is evolving on very short timescales of decades; they found that the spectrum observed by JWST differs from the earlier spectrum detected by Spitzer. According to Chengyan Xie, a second-year doctoral student at LPL who leads this in-progress work, this mismatch could be explained by a small, asymmetric disk inside of T Cha that has lost some of its mass in the short 17 years that have elapsed between the two observations.

"Along with the other studies, this also hints that the disk of T Cha is at the end of its evolution," Xie said. "We might be able to witness the dispersal of all the dust mass in T Cha's inner disk within our lifetime."

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Moon rocks with unique dust found

Our Earth's Moon is almost completely covered in dust. Unlike on Earth, this dust is not smoothed by wind and weather, but is sharp-edged and also electrostatically charged. This dust has been studied since the Apollo era at the end of the 1960s. Now, an international research team led by Dr. Ottaviano Rüsch from the University of Münster has for the first time discovered anomalous meter-sized rocks on the lunar surface that are covered in dust and presumably exhibit unique properties -- such as magnetic anomalies. The scientists' most important finding is that only very few boulders on the Moon have a layer of dust with very special reflective properties. For example, the dust on these newly discovered boulders reflects sunlight differently than on previously known rocks. These new findings help scientists to understand the processes that form and change the lunar crust. The results of the study have been published in the Journal of Geophysical Research -- Planets.

It is known that there are magnetic anomalies on the lunar surface, particularly near a region called Reiner Gamma.

However, the question of whether rocks can be magnetic has never been investigated.

"Current knowledge of the Moon's magnetic properties is very limited, so these new rocks will shed light on the history of the Moon and its magnetic core," says Ottaviano Rüsch from the 'Institut für Planetologie', categorizing the discovery.

"For the first time, we have investigated the interactions of dust with rocks in the Reiner Gamma region -- more precisely, the variations in the reflective properties of these rocks. For example, we can deduce to what extent and in which direction the sunlight is reflected by these large rocks." The images were taken by NASA's Lunar Reconnaissance Orbiter spacecraft, which orbits the Moon.

The research team was originally interested in cracked rocks.

They first used artificial intelligence to search through around one million images for fractured rocks -- these images were also taken by the Lunar Reconnaissance Orbiter.

"Modern data processing methods allow us to gain completely new insights into global contexts -- at the same time, we keep finding unknown objects in this way, such as the anomalous rocks that we are investigating in this new study," says Valentin Bickel from the Center for Space and Habitability at the University of Bern.

The search algorithm identified around 130,000 interesting rocks, half of which were scrutinized by the scientists.

"We recognized a boulder with distinctive dark areas on just one image. This rock was very different from all the others, as it scatters less light back towards the sun than other rocks. We suspect that this is due to the particular dust structure, such as the density and grain size of the dust," Ottaviano Rüsch explains.

"Normally, lunar dust is very porous and reflects a lot of light back in the direction of illumination. However, when the dust is compacted, the overall brightness usually increases. This is not the case with the observed dust-covered rocks," adds Marcel Hess from TU Dortmund University.

This is a fascinating discovery -- however, the scientists are still in the early stages of understanding this dust and its interactions with the rock.

In the coming weeks and months, the scientists want to further investigate the processes that lead to the interactions between dust and rocks and to the formation of the special dust structure.

These processes include, for example, the lifting of the dust due to electrostatic charging or the interaction of the solar wind with local magnetic fields.

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Dwarf galaxies use 10-million-year quiet period to churn out stars

If you look at massive galaxies teeming with stars, you might be forgiven in thinking they are star factories, churning out brilliant balls of gas. But actually, less evolved dwarf galaxies have bigger regions of star factories, with higher rates of star formation.

Now, University of Michigan researchers have discovered the reason underlying this: These galaxies enjoy a 10-million-year delay in blowing out the gas cluttering up their environments.

Star-forming regions are able to hang on to their gas and dust, allowing more stars to coalesce and evolve.

In these relatively pristine dwarf galaxies, massive stars -- stars about 20 to 200 times the mass of our sun -- collapse into black holes instead of exploding as supernovae.

But in more evolved, polluted galaxies, like our Milky Way, they are more likely to explode, thereby generating a collective superwind.

Gas and dust get blasted out of the galaxy, and star formation quickly stops.

Their findings are published in the Astrophysical Journal.

"As stars go supernova, they pollute their environment by producing and releasing metals," said Michelle Jecmen, study first author and an undergraduate researcher.

"We argue that at low metallicity -- galaxy environments that are relatively unpolluted -- there is a 10-million-year delay in the start of strong superwinds, which, in turn, results in higher star formation."

The U-M researchers point to what's called the Hubble tuning fork, a diagram that depicts the way astronomer Edwin Hubble classified galaxies.

In the handle of the tuning fork are the largest galaxies. Huge, round and brimming with stars, these galaxies have already turned all of their gas into stars.

Along the tines of the tuning fork are spiral galaxies that do have gas and star-forming regions along their compact arms.

At the end of the tuning fork's tines are the least evolved, smallest galaxies.

"But these dwarf galaxies have just these really mondo star-forming regions," said U-M astronomer Sally Oey, senior author of the study.

"There have been some ideas around why that is, but Michelle's finding offers a very nice explanation: These galaxies have trouble stopping their star formation because they don't blow away their gas."

Additionally, this 10-million-year period of quiet offers astronomers the opportunity to peer at scenarios similar to the cosmic dawn, a period of time just after the Big Bang, Jecmen said.

In pristine dwarf galaxies, gas clumps together and forms gaps through which radiation can escape.

This previously known phenomenon is called the "picket fence" model, with UV radiation escaping between slats in the fence.

The delay explains why gas would have had time to clump together.

Ultraviolet radiation is important because it ionizes hydrogen -- a process that also occurred right after the Big Bang, causing the universe to go from opaque to transparent.

"And so looking at low-metallicity dwarf galaxies with lots of UV radiation is somewhat similar to looking all the way back to the cosmic dawn," Jecmen said.

"Understanding the time near the Big Bang is so interesting. It's foundational to our knowledge. It's something that happened so long ago -- it's so fascinating that we can see sort of similar situations in galaxies that exist today."

A second study, published in the Astrophysical Journal Letters and led by Oey, used the Hubble Space Telescope to look at Mrk 71, a region in a nearby dwarf galaxy about 10 million light years away.

In Mrk 71, the team found observational evidence of Jecmen's scenario.

Using a new technique with the Hubble Space Telescope, the team employed a filter set that looks at the light of triply ionized carbon.

In more evolved galaxies with lots of supernova explosions, those explosions heat gas in a star cluster to very high temperatures -- to millions of degrees Kelvin, Oey said.

As this hot superwind expands, it blasts the rest of the gas out of the star clusters.

But in low metallicity environments such as Mrk 71, where stars aren't blowing up, energy within the region is radiated away.

It doesn't have the chance to form a superwind.

The team's filters picked up a diffuse glow of the ionized carbon throughout Mrk 71, demonstrating that the energy is radiating away.

Therefore, there is no hot superwind, instead allowing dense gas to remain throughout the environment.

Read more at Science Daily

Finding explanation for Milky Way's warp

The Milky Way is often depicted as a flat, spinning disk of dust, gas, and stars. But if you could zoom out and take an edge-on photo, it actually has a distinctive warp -- as if you tried to twist and bend a vinyl LP.

Though scientists have long known through observational data that the Milky Way is warped and its edges are flared like a skirt, no one could explain why.

Now, Harvard astronomers at the Center for Astrophysics | Harvard and Smithsonian (CfA) have performed the first calculations that fully explain this phenomenon, with compelling evidence pointing to the Milky Way's envelopment in an off-kilter halo of dark matter. The work also bolsters current thinking about how the galaxy evolved and may offer clues into some of the mysteries of dark matter.

The new calculations were led by Jiwon Jesse Han, a Griffin Graduate School of Arts and Sciences student affiliated with the CfA. Published in Nature Astronomy, the work includes co-authors Charlie Conroy and Lars Hernquist, both faculty members at the CfA and in the Department of Astronomy.

Our galaxy is located inside a diffuse cloud called the stellar halo, which extends much farther out into the universe. In groundbreaking work published last year, the Harvard team deduced that the stellar halo is tilted and elliptical in shape, like a zeppelin or football.

Building on that, the team assumed the same shape for the dark matter halo, the larger entity that encompasses everything in and around the Milky Way. Dark matter makes up 80 percent of the galaxy's mass but is invisible because it doesn't interact with light, so the shape of that halo must be inferred. Using models to calculate the orbits of stars within a tilted, oblong dark matter halo, the team found a near-perfect match to existing observations of a warped, flared galaxy.

"A tilted dark halo is actually fairly common in simulations, but no one had explored its effect on the Milky Way," Conroy said. "It turns out that the tilt is an elegant way to explain both the magnitude and direction of our galaxy's wobbly disk."

Scientists had long surmised that the Milky Way formed due to a galactic collision; the astronomers' work further underscores that hypothesis.

"If the galaxy was just evolving on its own, it would have had this nice, spherical halo, this nice, flat disk," Han said. "So the fact that the halo is tilted and has a football-like shape suggests that our galaxy experienced a merger event, where two galaxies collide."

Their calculation of the dark matter halo's probable shape may also provide clues as to the properties and particle nature of dark matter itself, which remain unsolved mysteries in physics. "The fact that the galaxy is not spherical in our data implies that there is some limit to which dark matter can interact with itself," Han explained.

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Webb locates dust reservoirs in two supernovae

Researchers using NASA's James Webb Space Telescope have made major strides in confirming the source of dust in early galaxies. Observations of two Type II supernovae, Supernova 2004et (SN 2004et) and Supernova 2017eaw (SN 2017eaw), have revealed large amounts of dust within the ejecta of each of these objects. The mass found by researchers supports the theory that supernovae played a key role in supplying dust to the early universe.

Dust is a building block for many things in our universe -- planets in particular. As dust from dying stars spreads through space, it carries essential elements to help give birth to the next generation of stars and their planets. Where that dust comes from has puzzled astronomers for decades. One significant source of cosmic dust could be supernovae -- after the dying star explodes, its leftover gas expands and cools to create dust.

"Direct evidence of this phenomenon has been slim up to this point, with our capabilities only allowing us to study the dust population in one relatively nearby supernova to date -- Supernova 1987A, 170,000 light-years away from Earth," said lead author Melissa Shahbandeh of Johns Hopkins University and the Space Telescope Science Institute in Baltimore, Maryland. "When the gas cools enough to form dust, that dust is only detectable at mid-infrared wavelengths provided you have enough sensitivity."

For supernovae more distant than SN 1987A like SN 2004et and SN 2017eaw, both in NGC 6946 about 22 million light-years away, that combination of wavelength coverage and exquisite sensitivity can only be obtained with Webb's MIRI (Mid-Infrared Instrument).

The Webb observations are the first breakthrough in the study of dust production from supernovae since the detection of newly formed dust in SN 1987A with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope nearly a decade ago.

Another particularly intriguing result of their study isn't just the detection of dust, but the amount of dust detected at this early stage in the supernova's life. In SN 2004et, the researchers found more than 5,000 Earth masses of dust.

"When you look at the calculation of how much dust we're seeing in SN 2004et especially, it rivals the measurements in SN 1987A, and it's only a fraction of the age," added program lead Ori Fox of the Space Telescope Science Institute. "It's the highest dust mass detected in supernovae since SN 1987A."

Observations have shown astronomers that young, distant galaxies are full of dust, but these galaxies are not old enough for intermediate mass stars, like the Sun, to have supplied the dust as they age. More massive, short-lived stars could have died soon enough and in large enough numbers to create that much dust.

While astronomers have confirmed that supernovae produce dust, the question has lingered about how much of that dust can survive the internal shocks reverberating in the aftermath of the explosion. Seeing this amount of dust at this stage in the lifetimes of SN 2004et and SN 2017eaw suggests that dust can survive the shockwave -- evidence that supernovae really are important dust factories after all.

Researchers also note that the current estimations of the mass may be the tip of the iceberg. While Webb has allowed researchers to measure dust cooler than ever before, there may be undetected, colder dust radiating even farther into the electromagnetic spectrum that remains obscured by the outermost layers of dust.

The researchers emphasized that the new findings are also just a hint at newfound research capabilities into supernovae and their dust production using Webb, and what that can tell us about the stars from which they came.

"There's a growing excitement to understand what this dust also implies about the core of the star that exploded," Fox said. "After looking at these particular findings, I think our fellow researchers are going to be thinking of innovative ways to work with these dusty supernovae in the future."

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Hidden views of vast stellar nurseries

Using ESO's Visible and Infrared Survey Telescope for Astronomy (VISTA), astronomers have created a vast infrared atlas of five nearby stellar nurseries by piecing together more than one million images. These large mosaics reveal young stars in the making, embedded in thick clouds of dust. Thanks to these observations, astronomers have a unique tool with which to decipher the complex puzzle of stellar birth.

"In these images we can detect even the faintest sources of light, like stars far less massive than the Sun, revealing objects that no one has ever seen before," says Stefan Meingast, an astronomer at the University of Vienna in Austria and lead author of the new study published today in Astronomy & Astrophysics. "This will allow us to understand the processes that transform gas and dust into stars."

Stars form when clouds of gas and dust collapse under their own gravity, but the details of how this happens are not fully understood. How many stars are born out of a cloud? How massive are they? How many stars will also have planets?

To answer these questions, Meingast's team surveyed five nearby star-forming regions with the VISTA telescope at ESO's Paranal Observatory in Chile. Using VISTA's infrared camera VIRCAM, the team captured light coming from deep inside the clouds of dust. "The dust obscures these young stars from our view, making them virtually invisible to our eyes. Only at infrared wavelengths can we look deep into these clouds, studying the stars in the making," explains Alena Rottensteiner, a PhD student also at the University of Vienna and co-author of the study.

The survey, called VISIONS, observed star-forming regions in the constellations of Orion, Ophiuchus, Chamaeleon, Corona Australis and Lupus. These regions are less than 1500 light-years away and so large that they span a huge area in the sky. The diameter of VIRCAM's field of view is as wide as three full Moons, which makes it uniquely suited to map these immensely big regions.

The team obtained more than one million images over a period of five years. The individual images were then pieced together into the large mosaics released here, revealing vast cosmic landscapes. These detailed panoramas feature dark patches of dust, glowing clouds, newly-born stars and the distant background stars of the Milky Way.

Since the same areas were observed repeatedly, the VISIONS data will also allow astronomers to study how young stars move. "With VISIONS we monitor these baby stars over several years, allowing us to measure their motion and learn how they leave their parent clouds," explains João Alves, an astronomer at the University of Vienna and Principal Investigator of VISIONS. This is not an easy feat, as the apparent shift of these stars as seen from Earth is as small as the width of a human hair seen from 10 kilometres away. These measurements of stellar motions complement those obtained by the European Space Agency's Gaia mission at visible wavelengths, where young stars are hidden by thick veils of dust.

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New study puts a definitive age on Saturn's rings -- they're really young

A new study led by physicist Sascha Kempf at the University of Colorado Boulder has delivered the strongest evidence yet that Saturn's rings are remarkably young -- potentially answering a question that has boggled scientists for well over a century.

The research, to be published May 12 in the journal Science Advances, pegs the age of Saturn's rings at no more than 400 million years old. That makes the rings much younger than Saturn itself, which is about 4.5 billion years old.

"In a way, we've gotten closure on a question that started with James Clerk Maxwell," said Kempf, associate professor in the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder.

The researchers arrived at that closure by studying what might seem like an unusual subject: dust.

Kempf explained that tiny grains of rocky material wash through Earth's solar system on an almost constant basis. In some cases, this flux can leave behind a thin layer of dust on planetary bodies, including on the ice that makes up Saturn's rings.

In the new study, he and his colleagues set out to put a date on Saturn's rings by studying how rapidly this layer of dust builds up -- a bit like telling how old a house is by running your finger along its surfaces.

"Think about the rings like the carpet in your house," Kempf said. "If you have a clean carpet laid out, you just have to wait. Dust will settle on your carpet. The same is true for the rings."

It was an arduous process: From 2004 to 2017, the team used an instrument called the Cosmic Dust Analyzer aboard NASA's late Cassini spacecraft to analyze specks of dust flying around Saturn. Over those 13 years, the researchers collected just 163 grains that had originated from beyond the planet's close neighborhood. But it was enough. Based on their calculations, Saturn's rings have likely been gathering dust for only a few hundred million years.

The planet's rings, in other words, are new phenomena, arising (and potentially even disappearing) in what amounts to a blink of an eye in cosmic terms.

"We know approximately how old the rings are, but it doesn't solve any of our other problems," Kempf said. "We still don't know how these rings formed in the first place."

From Galileo to Cassini

Researchers have been captivated by these seemingly-translucent rings for more than 400 years. In 1610, Italian astronomer Galileo Galilei first observed the features through a telescope, although he didn't know what they were. (Galileo's original drawings make the rings look a bit like the handles on a water jug). In the 1800s, Maxwell, a scientist from Scotland, concluded that Saturn's rings couldn't be solid but were, instead, made up of many individual pieces.

Today, scientists know that Saturn hosts seven rings comprised of countless chunks of ice, most no bigger than a boulder on Earth. Altogether, this ice weighs about half as much as Saturn's moon Mimas and stretches nearly 175,000 miles from the planet's surface.

Kempf added that for most of the 20th Century, scientists assumed that the rings likely formed at the same time as Saturn.

But that idea raised a few issues -- namely, Saturn's rings are sparkling clean. Observations suggest that these features are made up of roughly 98% pure water ice by volume, with only a tiny amount of rocky matter.

"It's almost impossible to end up with something so clean," Kempf said.

Cassini offered an opportunity to put a definitive age on Saturn's rings. The spacecraft first arrived at Saturn in 2004 and collected data until it purposefully crashed into the planet's atmosphere in 2017. The Cosmic Dust Analyzer, which was shaped a bit like a bucket, scooped up small particles as they whizzed by.

Engineers and scientists at LASP designed and built a much more sophisticated dust analyzer for NASA's upcoming Europa Clipper mission, which is scheduled to launch in 2024.

The team estimated that this interplanetary grime would contribute far less than a gram of dust to each square foot of Saturn's rings every year -- a light sprinkle, but enough to add up over time. Previous studies had also suggested that the rings could be young but didn't include definitive measures of dust accumulation.

Stroke of luck

The rings might already be vanishing. In a previous study, NASA scientists reported that the ice is slowly raining down onto the planet and could disappear entirely in another 100 million years.

That these ephemeral features existed at a time when Galileo and the Cassini spacecraft could observe them seems almost too good to be true, Kempf said -- and it begs an explanation for how the rings formed in the first place. Some scientists, for example, have posited that Saturn's rings may have formed when the planet's gravity tore apart one of its moons.

"If the rings are short lived and dynamical, why are we seeing them now?" he said. "It's too much luck."

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Hubble follows shadow play around planet-forming disk

The young star TW Hydrae is playing "shadow puppets" with scientists observing it with NASA's Hubble Space Telescope.

In 2017, astronomers reported discovering a shadow sweeping across the face of a vast pancake-shaped gas-and-dust disk surrounding the red dwarf star. The shadow isn't from a planet, but from an inner disk slightly inclined relative to the much larger outer disk -- causing it to cast a shadow. One explanation is that an unseen planet's gravity is pulling dust and gas into the planet's inclined orbit.

Now, a second shadow -- playing a game of peek-a-boo -- has emerged in just a few years between observations stored in Hubble's MAST archive. This could be from yet another disk nestled inside the system. The two disks are likely evidence of a pair of planets under construction.

TW Hydrae is less than 10 million years old and resides about 200 light-years away. In its infancy, our solar system may have resembled the TW Hydrae system, some 4.6 billion years ago. Because the TW Hydrae system is tilted nearly face-on to our view from Earth, it is an optimum target for getting a bull's-eye-view of a planetary construction yard.

The second shadow was discovered in observations obtained on June 6, 2021, as part of a multi-year program designed to track the shadows in circumstellar disks. John Debes of AURA/STScI for the European Space Agency at the Space Telescope Science Institute in Baltimore, Maryland, compared the TW Hydrae disk to Hubble observations made several years ago.

"We found out that the shadow had done something completely different," said Debes, who is principal investigator and lead author of the study published in The Astrophysical Journal. "When I first looked at the data, I thought something had gone wrong with the observation because it wasn't what I was expecting. I was flummoxed at first, and all my collaborators were like: what is going on? We really had to scratch our heads and it took us a while to actually figure out an explanation."

The best solution the team came up with is that there are two misaligned disks casting shadows. They were so close to each other in the earlier observation they were missed. Over time they've now separated and split into two shadows. "We've never really seen this before on a protoplanetary disk. It makes the system much more complex than we originally thought," he said.

The simplest explanation is that the misaligned disks are likely caused by the gravitational pull of two planets in slightly different orbital planes. Hubble is piecing together a holistic view of the architecture of the system.

The disks may be proxies for planets that are lapping each other as they whirl around the star. It's sort of like spinning two vinyl phonograph records at slightly different speeds. Sometimes labels will match up but then one gets ahead of the other.

"It does suggest that the two planets have to be fairly close to each other. If one was moving much faster than the other, this would have been noticed in earlier observations. It's like two race cars that are close to each other, but one slowly overtakes and laps the other," said Debes.

The suspected planets are located in a region roughly the distance of Jupiter from our Sun. And, the shadows complete one rotation around the star about every 15 years -- the orbital period that would be expected at that distance from the star.

Also, these two inner disks are inclined about five to seven degrees relative to the plane of the outer disk. This is comparable to the range of orbital inclinations inside our solar system. "This is right in line with typical solar system style architecture," said Debes.

The outer disk that the shadows are falling on may extend as far as several times the radius of our solar system's Kuiper belt. This larger disk has a curious gap at twice Pluto's average distance from the Sun. This might be evidence for a third planet in the system.

Any inner planets would be difficult to detect because their light would be lost in the glare of the star. Also, dust in the system would dim their reflected light. ESA's Gaia space observatory may be able to measure a wobble in the star if Jupiter-mass planets are tugging on it, but this would take years given the long orbital periods.

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Twinkling stars fuel interstellar dust

Of the many different kinds of stars, asymptotic giant branch (AGB) stars, usually slightly larger and older than our own sun, are known producers of interstellar dust. Dusty AGBs are particularly prominent producers of dust, and the light they shine happens to vary widely. For the first time, a long-period survey has found the variable intensity of dusty AGBs coincides with variations in the amount of dust these stars produce. As this dust can lead to the creation of planets, its study can shed light on our own origins.

You've probably heard of the James Webb Space Telescope (JWST) which has been in the news lately. It's famous for being the largest and most sensitive space telescope designed to observe infrared (IR) light. But long before the JWST took to the skies, two other IR space telescopes, AKARI and WISE, have been surveying the cosmos, both of which have ended their initial missions, but produced so much valuable data that astronomers are still finding new discoveries with it. The latest finding from that data by doctoral student Kengo Tachibana from the University of Tokyo's Institute of Astronomy and his team, could have implications for the study of the origins of life itself.

"We study stars, and IR light from them is a key source of information that helps us unlock their secrets," said Tachibana. "Until recently, most IR data was from very short-period surveys due to the lack of advanced dedicated platforms. But missions like AKARI and WISE have allowed us to take longer-period surveys of things. This means we can see how things might change over greater time periods, and what these changes might imply. Lately, we turned our attention to a certain class of star known as asymptotic giant branch stars, which are interesting because they are the main producers of interstellar dust."

This interstellar dust is not the same stuff that accumulates on your floor when you forget to vacuum for a few days; it's a name given to heavy elements that disperse from stars and lead to the formation of solid objects including planets. Although it's long been known that AGBs, and especially so-called dusty AGBs, are the main producers of dust, it's not known what the main drivers of dust production are and where we should be looking to find this out.

"Our latest study has pointed us in the right direction," said Tachibana. "Thanks to long-period IR observations, we have found that the light from dusty AGBs varies with periods longer than several hundred days. We also found that the spherical shells of dust produced by and then ejected by these stars have concentrations of dust that vary in step with the stars' changes in luminosity. Of the 169 dusty AGBs surveyed, no matter their variability period, the concentrations of dust around them would coincide. So, we're certain these are connected."

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How were amino acids, one of the key building blocks of life, formed before the origin of life on Earth?

Our solar system formed from a molecular cloud, which was composed of gas and dust that was emitted into the interstellar medium (ISM), a vast space between stars. On collapse of the molecular cloud, the early sun was formed, with a large disk of gas and dust orbiting it. The dusty material collided to produce rocky material that would eventually grow in size to give large bodies called planetesimals.

The planetesimals that formed far enough from the sun, also contained large quantities of ice. The ice consisted of water and other volatile compounds, such as carbon monoxide (CO), carbon dioxide (CO2), methanol (CH3OH) and ammonia (NH3), as well as many other organic compounds, likely including some amino acids. Eventually, the ice melted due to the presence of radioactive material that heated up the bodies. This period of liquid water (termed aqueous alteration) enabled many reactions to occur, including Strecker synthesis and Formose-like reactions, the result being the production of new organic material, including amino acids. The same process also changed the rocky materials from their original minerals to new secondary minerals, such as phyllosilicates, carbonates, Fe-oxides and Fe-sulfides.

After several millions of years, the planetesimals began to freeze, as the radioactive material was used up. Later catastrophic collisions and interaction with the solar systems planets broke up the large bodies and sent their asteroidal and cometary fragments close to Earth. Further impact events have since delivered fragments of these asteroids and comets to the Earth's surface, supplying the Earth with large quantities of organic material, including amino acids, over the course of its history.

Amino acids are within all living things on Earth, being the building blocks of proteins. Proteins are essential for many processes within living organisms, including catalysing reactions (enzymes), replicating genetic material (ribosomes), transporting molecules (transport proteins) and providing a structure to cells and organisms (e.g. collagen). Therefore, amino acids would have been needed in significant amounts within the region where life began on Earth.

Previous work has identified a number of possible settings both on the Early Earth and in extraterrestrial environments that can form amino acids. Interestingly, most amino acids come in at least two forms, whose structures represent mirror images of each other, similar to human hands. Accordingly, these are often referred to as the right-handed or left-handed optical isomers. One interesting characteristic of life on Earth is that it uses one particular type of amino acids in its proteins, the left-handed optical isomer. Currently, only a certain class of meteorites (carbonaceous chondrites) are known to contain excesses of left-handed optical isomers, which has led to the idea that the amino acids used by life may have originated from these meteorites. Despite this, the amino acids in meteorites could have formed before their incorporation into the meteorites or after the meteorites had already formed.

Here, a team of scientists analysed several fragments of the asteroid Ryugu and calculated the abundance of amino acids within them. The abundance of the mineral phases within the particles had been previously reported in another publication, which allowed for a comparison between the abundance of amino acids and minerals. It was found that one particle (A0022) contained a high abundance of an amino acid that is uncommon in extraterrestrial materials, called dimethylglycine (DMG), whereas the other particle (C0008) did not contain this amino acid above detection limit. Meanwhile, the abundance of the amino acid glycine was found to be lower in A0022 compared to C0008, while the abundance of β-Alanine showed the opposite trend. Accordingly, the ratio of β-Alanine to glycine was higher for A0022 than for C0008. This ratio was shown previously to be indicative of the extent of aqueous alteration operating on planetesimals. Accordingly, it was hypothesised that some reaction related to higher levels of aqueous alteration in A0022 may explain the high abundance of DMG in this particle, compared to C0008.

As such, the mineral phases were examined to see if any additional evidence for what reaction may be causing the different amino acids abundances between the Ryugu particles. It was found that the abundance of secondary minerals (formed after aqueous alteration), including carbonate, magnetite and Fe-sulfides, was higher in A0022 than in C0008. In particular, the high abundance of carbonate pointed towards a larger quantity of CO or CO2 within the region of the planetesimal where A0022 had been altered, compared to C0008. In conjunction with the evidence for more intense aqueous alteration from the β-Alanine to glycine ratio, this indicated that more ice in general may have been present in the precursor of A0022 than in C0008.

One way to commercially produce DMG, an important nutrient for humans, is the through the Eschweiler-Clarke reaction. This reaction requires the interaction of glycine with formic acid and formaldehyde in water and also produces CO2. Glycine, formaldehyde and formic acid are all found in comets and so it is expected that they would be present in the planetesimal precursors of asteroids. Therefore, if the Eschweiler-Clarke reaction occurred during aqueous alteration within the precursor of A0022, then it could explain the high level of DMG and lower abundance of glycine in this particle, compared to C0008. Additionally, the CO2 produced could have further contributed to the formation of carbonates in A0022.

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Scientists develop a 'cosmic concrete' that is twice as strong as regular concrete

Manchester scientists have created a new material, dubbed 'StarCrete' which is made from extra-terrestrial dust, potato starch, and a pinch of salt and could be used to build homes on Mars.

Building infrastructure in space is currently prohibitively expensive and difficult to achieve. Future space construction will need to rely on simple materials that are easily available to astronauts, StarCrete offers one possible solution. The scientists behind the invention used simulated Martian soil mixed with potato starch and a pinch of salt to create the material that is twice as strong as ordinary concrete and is perfectly suited for construction work in extra-terrestrial environments.

In an article published in the journal Open Engineering [EB1] , the research team demonstrated that ordinary potato starch can act as a binder when mixed with simulated Mars dust to produce a concrete-like material. When tested, StarCrete had a compressive strength of 72 Megapascals (MPa), which is over twice as strong as the 32 MPa seen in ordinary concrete. Starcrete made from moon dust was even stronger at over 91 MPa.

This work improves on previous work from the same team where they used astronauts' blood and urine as a binding agent. While the resulting material had a compressive strength of around 40 MPa, which is better than normal concrete, the process had the drawback of requiring blood on a regular basis. When operating in an environment as hostile as space, this option was seen as less feasible than using potato starch.

"Since we will be producing starch as food for astronauts, it made sense to look at that as a binding agent rather than human blood. Also, current building technologies still need many years of development and require considerable energy and additional heavy processing equipment which all adds cost and complexity to a mission. StarCrete doesn't need any of this and so it simplifies the mission and makes it cheaper and more feasible.

"And anyway, astronauts probably don't want to be living in houses made from scabs and urine!" Dr Aled Roberts, Research Fellow at the Future Biomanufacturing Research Hub, and lead researcher for this project.

The team calculate that a sack (25 Kg) of dehydrated potatoes (crisps) contain enough starch to produce almost half a tonne of StarCrete, which is equivalent to over 213 brick's worth of material. For comparison, a 3-bedroom house takes roughly 7,500 bricks to build. Additionally, they discovered that a common salt, magnesium chloride, obtainable from the Martian surface or from the tears of astronauts, significantly improved the strength of StarCrete.

The next stages of this project are to translate StarCrete from the lab to application. Dr Roberts and his team have recently launched a start-up company, DeakinBio, which is exploring ways to improve StarCrete so that it could also be used in a terrestrial setting.

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A mysterious object is being dragged into the supermassive black hole at the Milky Way's center

For two decades, scientists have observed an elongated object named X7 near the supermassive black hole at the center of the Milky Way and wondered what it was. Was it pulled off a larger structure nearby? Was its unusual form the result of stellar winds or was it shaped by jets of particles from the black hole?

Now, having examined the evolution of X7 using 20 years of data gathered by the Galactic Center Orbit Inintiative, astronomers from the UCLA Galactic Center Group and the Keck Observatory propose that it could be a cloud of dust and gas that was ejected during the collision of two stars.

Over time, they report, X7 has stretched, and it is being pulled apart as the black hole drags it closer, exerting its tidal force upon the cloud. They expect that within the next few decades, X7 will disintegrate and the gas and dust of which it is composed will eventually be drawn toward the black hole, which is called Sagittarius A*, or Sgr A*.

The study is published in The Astrophysical Journal.

"No other object in this region has shown such an extreme evolution," said Anna Ciurlo, a UCLA assistant researcher and the paper's lead author. "It started off comet-shaped and people thought maybe it got that shape from stellar winds or jets of particles from the black hole. But as we followed it for 20 years we saw it becoming more elongated. Something must have put this cloud on its particular path with its particular orientation."

X7 has a mass of about 50 Earths and is on an orbital path around Sgr A* that would take 170 years to complete.

But that might never happen. Based on its trajectory, the team estimates that X7 will make its closest approach to Sgr A* around the year 2036, and then likely spiral toward Sgr A* and disappear.

"We anticipate the strong tidal forces exerted by the galactic black hole will ultimately tear X7 apart before it completes even one orbit," said co-author Mark Morris, UCLA professor of physics and astronomy.

Tidal forces are the gravitational pull that cause an object approaching a black hole to stretch; the side of the object closest to the black hole is pulled much more strongly than the opposite end.

X7 shows some of the same properties as the other strange dusty objects orbiting Sgr A*. Those so-called G objects look like gas but behave like stars. But X7's shape and velocity have changed more dramatically than G objects' have. As it accelerates toward the black hole, X7 is moving rapidly, clocking in at speeds of up to around 700 miles per second.

"It's exciting to see significant changes of X7's shape and dynamics in such great detail over a relatively short time scale as the gravitational forces of the supermassive black hole at the center of the Milky Way influences this object," Randy Campbell, a co-author of the paper and the science operations lead at the Keck Observatory, said in a statement.

Although X7's origin is still the subject of debate, the finding suggests that it arose after two stars collided.

"One possibility is that X7's gas and dust were ejected at the moment when two stars merged," Ciurlo said. "In this process, the merged star is hidden inside a shell of dust and gas, which might fit the description of the G objects. And the ejected gas perhaps produced X7-like objects."

The merger of two stars is very common, especially when they are near black holes, Ciurlo said.

"This is a very messy process: The stars circle each other, get closer, merge, and the new star is hidden within a cloud of dust and gas," she said. "X7 could be the dust and gas ejected from a merged star that's still out there somewhere."

The findings are the first estimate of X7's mildly elliptical orbit and the most robust analysis to date of the remarkable changes to its appearance, shape and behavior. The research team will continue to use the Keck Observatory to monitor X7's dramatic changes as the power of the black hole's gravity yanks it apart.

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Geoengineering to cool earth: Space dust as Earth's sun shield

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 paper was published on Wednesday, Feb. 8, 2023, in the journal PLOS Climate.

Casting a shadow

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.

Just a moonshot?

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."

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Researchers complete first real-world study of Martian helicopter dust dynamics

Mars is a dusty planet. From tiny dust devils to vast storms that shroud the planet, dust is a constant challenge for research missions. That was especially true for Ingenuity, the rotorcraft that since February 2021 has been exploring Mars alongside NASA's Perseverance rover. Now, researchers at Stevens Institute of Technology, the Space Science Institute, and the Jet Propulsion Laboratory have completed the first real-world study of Martian dust dynamics based on Ingenuity's historic first flights on the Red Planet, paving the way for future extraterrestrial rotorcraft missions.

The work, reported in the December 2022 issue of Journal of Geophysical Research: Planets, could support NASA's Mars Sample Return Program, which will retrieve samples collected by Perseverance, or the Dragonfly mission that will set course for Titan, Saturn's largest moon, in 2027.

"There's a reason that helicopter pilots on Earth prefer to land on helipads," said Jason Rabinovitch, a co-author and assistant professor at Stevens. "When a helicopter lands in the desert, its downdraft can stir up enough dust to cause a zero-visibility 'brownout' -- and Mars is effectively one big desert."

Rabinovitch has been working on the Ingenuity program since 2014, joining the Jet Propulsion Laboratory soon after the concept was first pitched to NASA and creating the first theoretical models of helicopter dust lifting in the dusty Martian environments. At Stevens, Rabinovitch continues to work with JPL and investigates plume-surface interactions during powered descent of a spacecraft. He also models supersonic parachute inflation and geophysical phenomena, such as plumes on Enceladus.

Studying dust dynamics on another planet isn't easy, explained Rabinovitch. "Space is a data-poor environment. It's hard to send videos and images back to Earth, so we have to work with what we can get."

To overcome that challenge, Rabinovitch and colleagues at JPL used advanced image-processing techniques to extract information from six helicopter flights, all low-resolution videos captured by Perseverance. By identifying tiny variations between video frames, and the light intensity of individual pixels, the researchers were able to calculate both the size and the total mass of dust clouds kicked up as Ingenuity took off, hovered, maneuvered, and landed.

The results were within striking distance of Rabinovitch's engineering models -- itself a remarkable achievement, given the limited information available to the team way back in 2014, when Rabinovitch and his colleagues were writing back-of-the-envelope calculations intended to support the original design of Ingenuity.

The research shows that, as predicted, dust is a significant consideration for extra-terrestrial rotorcraft, with Ingenuity estimated to have kicked up about a thousandth of its own mass (four pounds) in dust each time it flew. That's many times more dust than would be generated by an equivalent helicopter on Earth, though Rabinovitch cautions that it's tricky to draw direct comparisons.

"It was exciting to see the Mastcam-Z video from Perseverance, which was taken for engineering reasons, ended up showing Ingenuity lifting so much dust from the surface that it opened a new line of research," said Mark Lemmon, senior research scientist at the Space Science Institute Mars Science Laboratory and first author of the study.

"When you think about dust on Mars, you have to consider not just the lower gravity, but also the effects of air pressure, temperature, air density -- there's a lot we don't yet fully understand," Rabinovich said. Still, he added, that's what makes studying Ingenuity's dust clouds so exciting.

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Dust plumes observed being 'pushed' into interstellar space by intense starlight

The results, made using infrared images of the binary star system WR140 taken over 16 years, are reported in the journal Nature.

In a complementary study of WR140, published in Nature Astronomy, NASA's James Webb Space Telescope (JWST) was able to see much deeper to snap an image of not just a single accelerating dust plume, but almost 20 of them, nested inside each other like a giant set of onion skins.

WR140 is comprised of a huge Wolf-Rayet star and an even bigger blue supergiant star, gravitationally bound in an eight-year orbit. This binary star, in the Cygnus constellation, has been monitored for two decades with one of the world's largest optical telescopes at the Keck Observatory in Hawaii.

WR140 episodically puffs out plumes of dust stretching thousands of times the distance from the Earth to the Sun. These dust plumes, produced every eight years, give astronomers a unique opportunity to observe how starlight can affect matter.

It's known that light carries momentum, exerting a push on matter known as radiation pressure. Astronomers often witness the outcome of this phenomenon in the form of matter coasting at high speed around the cosmos, but it's been a difficult process to catch in the act. Direct recording of acceleration due to forces other than gravity is rarely witnessed, and never in a stellar environment like this.

"It's hard to see starlight causing acceleration because the force fades with distance, and other forces quickly take over," said Yinuo Han from Cambridge's Institute of Astronomy, first author of the Nature paper. "To witness acceleration at the level that it becomes measurable, the material needs to be reasonably close to the star or the source of the radiation pressure needs to be extra strong. WR140 is a binary star whose ferocious radiation field supercharges these effects, placing them within reach of our high-precision data."

All stars generate stellar winds, but those from Wolf-Rayet stars can be more like a stellar hurricane. Elements such as carbon in the wind condense out as soot, which remains hot enough to glow bright in the infrared. Like smoke in the wind, this gives telescopes something that can be observed.

The team used an imaging technology known as interferometry which was able to act like a zoom lens for the 10-metre Keck telescope mirror, enabling the researchers to recover sufficiently sharp images of WR140 for the study.

Han and his team found that the dust does not stream out from the star with the wind in a hazy ball. Instead, the dust forms where the winds from the two stars collide, on the surface of a cone-shaped shock front between them.

Because the orbiting binary star is in constant motion, the shock front also rotates. The sooty plume gets wrapped into a spiral, in the same way that droplets form a spiral in a garden sprinkler.

The researchers found that WR140 has other tricks up its sleeve. The two stars are not on circular but rather elliptical orbits, and dust production turns on and off as the binary nears and departs the point of closest approach. By modelling these effects into the three-dimensional geometry of the dust plume, the astronomers were able to measure to location of dust features in three-dimensional space.

"Like clockwork, this star puffs out sculpted smoke rings every eight years, with all this wonderful physics written then inflated in the wind like a banner for us to read," said co-author Professor Peter Tuthill from the University of Sydney. "Eight years later as the binary returns in its orbit, another appears the same as the one before, streaming out into space inside the bubble of the previous one, like a set of giant nested Russian dolls."

Because the dust produced by this Wolf-Rayet is so predictable and expands to such large distances, it offered the astronomers a unique laboratory to examine the acceleration zone.

"In the absence of external forces, each dust spiral should expand at a constant speed," said Han, who is also a co-author on the JWST paper. "We were puzzled at first because we could not get our model to fit the observations, until we finally realised that we were seeing something new. The data did not fit because the expansion speed wasn't constant, but rather that it was accelerating. We'd caught that for the first time on camera."

"In one sense, we always knew this must be the reason for the outflow, but I never dreamed we'd be able to see the physics at work like this," said Tuthill. "When I look at the data now, I see WR140's plume unfurling a like giant sail made of dust. When it catches the photon wind streaming from the star, like a yacht catching a gust, it makes a sudden leap forward."

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Why the Salton Sea is turning into toxic dust

The Salton Sea, California's most polluted inland lake, has lost a third of its water in the last 25 years. New research has determined a decline in Colorado River flow is the reason for that shrinking.

As the lake dries up, the concentration of salt and chemicals in the remaining water has increased dramatically, causing a mass die-off of fish and birds, including endangered species. The dry lakebed, coated in the salty, toxic water, becomes dust that causes respiratory problems for nearby residents.

"It is an environmental catastrophe," said Juan S. Acero Triana, UCR hydrologist and lead author of a new study focused on understanding water movement on and below Earth's surface near the Salton Sea, a research field called hydrology. The study was funded by the National Science Foundation's Innovation at the Nexus of Food, Energy and Water Systems, or INFEWS, program.

There have been a variety of hypotheses about why the water levels are steadily declining. Some blame climate change and heat for drying up the lake. Others suspect that agriculture could be to blame. As irrigation systems get more efficient and crops are modified to use less water, it means less water getting into the Salton Sea. However, the researchers say these are not the biggest causes of the sea's decline.

"There is less water coming from the Colorado River into the Sea, and that is driving the problem," said Hoori Ajami, UCR hydrologist, study co-author and principal investigator. This finding, and the methods used to obtain it, are now published in the journal Water Resources Research.

The researchers considered all major processes impacting the water balance of an endorheic lake like the Salton Sea, where water flows in but not out to any tributaries. Endorheic lakes worldwide have been shrinking in recent decades at what the researchers call an "alarming" rate due to the combined effects of global warming and diversion of water for agricultural and industrial purposes.

To understand the reasons for the Salton Sea's decline, the researchers used a hydrologic model that accounted for all processes in the surrounding areas that impact the lake's water balance, including climate, soil types, land slope, and plant growth.

Geographically the model included data not only about the Sea itself, but also from the surrounding watershed, streams entering the lake, and the land area that drains into those streams.

Data for the model was hard to come by as this is a transboundary basin on the US-Mexico border between California and Baja California Norte, and stakeholders may have been reluctant to share data that could alter previously earned water rights. However, using publicly available data and data mining techniques, UCR researchers were able to simulate long-term water balance dynamics and identify reduced Colorado River flows as the main cause of the Salton Sea shrinking.

"It's not entirely clear, however, whether the decline in Colorado River water is more due to global warming drying out the river, or reductions in allocation levels to California, or both," Acero Triana said.

Despite that lingering ambiguity, the researchers say the study should send a message to water management agencies and lawmakers that the Salton Sea watershed should be considered part of the Colorado River basin.

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