Researchers explore the effects of stellar magnetism on potential habitability of exoplanets

Interest in Earth-like planets orbiting within the habitable zone of their host stars has surged, driven by the quest to discover life beyond our solar system. But the habitability of such planets, known as exoplanets, is influenced by more than just their distance from the star.

A new study by Rice University's David Alexander and Anthony Atkinson extends the definition of a habitable zone for planets to include their star's magnetic field. This factor, well studied in our solar system, can have significant implications for life on other planets, according to the research published in The Astrophysical Journal on July 9.

The presence and strength of a planet's magnetic field and its interaction with the host star's magnetic field are pivotal factors in a planet's ability to support life. An exoplanet needs a strong magnetic field to protect it from stellar activity, and it must orbit far enough from its star to avoid a direct and potentially catastrophic magnetic connection.

"The fascination with exoplanets stems from our desire to understand our own planet better," said Alexander, professor of physics and astronomy, director of the Rice Space Institute and member of the Texas Aerospace Research and Space Economy Consortium. "Questions about the Earth's formation and habitability are the key drivers behind our study of these distant worlds."

Magnetic interactions

Traditionally, scientists have focused on the "Goldilocks Zone," the area around a star where conditions are just right for liquid water to exist. By adding the star's magnetic field to the habitability criteria, Alexander's team offers a more nuanced understanding of where life might thrive in the universe.

The investigation focused on the magnetic interactions between planets and their host stars, a concept known as space weather. On Earth, space weather is driven by the sun and affects our planet's magnetic field and atmosphere. For the study, the researchers simplified the complex modeling usually required to understand these interactions.

The researchers characterized stellar activity using a measure of a star's activity known as the Rossby number (Ro): the ratio of the star's rotation period to its convective turnover time. This helped them estimate the star's Alfvén radius -- the distance at which the stellar wind effectively becomes decoupled from the star.

Planets within this radius would not be viable candidates for habitability because they would be magnetically connected back to the star, leading to rapid erosion of their atmosphere.

By applying this approach, the team examined 1,546 exoplanets to determine if their orbits lay inside or outside their star's Alfvén radius.

Life elsewhere in the galaxy

The study found that only two planets, K2-3 d and Kepler-186 f, of the 1,546 examined met all the conditions for potential habitability. These planets are Earth-sized, orbit at a distance conducive to the formation of liquid water, lie outside their star's Alfvén radius and have strong enough magnetic fields to protect them from stellar activity.

"While these conditions are necessary for a planet to host life, they do not guarantee it," said Atkinson, a graduate student of physics and astronomy and lead author of the study. "Our work highlights the importance of considering a wide range of factors when searching for habitable planets."

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Scorching storms on distant worlds revealed

Astronomers have created the most detailed weather report so far for two distant worlds beyond our own solar system.

The international study -- the first of its kind -- reveals the extreme atmospheric conditions on the celestial objects, which are swathed in swirling clouds of hot sand amid temperatures of 950C.

Using NASA's powerful James Webb Space Telescope (JWST), researchers set out to capture the weather on a pair of brown dwarfs -- cosmic bodies that are bigger than planets but smaller than stars.

These brown dwarfs, named collectively as WISE 1049AB, are the brightest and closest objects of their type to Earth, around six light years away.

The team tracked each brown dwarf's atmosphere by measuring the light waves emitted from their surfaces, which change as more or less cloudy regions revolve in and out of view.

By visualising this data through light curves -- a plot of how the brightness of light from each object changes over time -- the team was able to build up a detailed 3D picture of how the brown dwarfs' weather changed over the course of a full rotation or day, between five and seven hours.

The team was also able to plot how the light from each object varied by wavelength, to demonstrate the presence and complex interplay of gases such as water, methane, and carbon monoxide in their atmospheres.

The insights may help astronomers develop the understanding of brown dwarfs as a potential missing link between stars and planets -- promising new insights into both.

By observing the infrared part of the light spectrum, the JWST is able to observe wavelengths of light that are blocked by our own atmosphere.

This capability opens frontiers in the study of the early universe, star formation, and so-called exoplanets such as brown dwarfs which lie beyond our solar system.

The latest study builds on previous studies of brown dwarfs, which have mainly been confined to capturing static snapshots of their atmosphere on only one side. This approach is limited, as brown dwarfs are known to rotate relatively quickly and their weather can vary greatly over time, researchers say.

Their findings will pave the way for more detailed studies into brown dwarfs and other distant celestial objects.

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NASA's Webb maps weather on planet 280 light-years away

An international team of researchers has successfully used NASA's James Webb Space Telescope to map the weather on the hot gas-giant exoplanet WASP-43 b.

Precise brightness measurements over a broad spectrum of mid-infrared light, combined with 3D climate models and previous observations from other telescopes, suggest the presence of thick, high clouds covering the nightside, clear skies on the dayside, and equatorial winds upwards of 5,000 miles per hour mixing atmospheric gases around the planet.

The investigation is just the latest demonstration of the exoplanet science now possible with Webb's extraordinary ability to measure temperature variations and detect atmospheric gases trillions of miles away.

Tidally Locked "Hot Jupiter"

WASP-43 b is a "hot Jupiter" type of exoplanet: similar in size to Jupiter, made primarily of hydrogen and helium, and much hotter than any of the giant planets in our own solar system. Although its star is smaller and cooler than the Sun, WASP-43 b orbits at a distance of just 1.3 million miles -- less than 1/25th the distance between Mercury and the Sun.

With such a tight orbit, the planet is tidally locked, with one side continuously illuminated and the other in permanent darkness. Although the nightside never receives any direct radiation from the star, strong eastward winds transport heat around from the dayside.

Since its discovery in 2011, WASP-43 b has been observed with numerous telescopes, including NASA's Hubble and now-retired Spitzer space telescopes.

"With Hubble, we could clearly see that there is water vapor on the dayside. Both Hubble and Spitzer suggested there might be clouds on the nightside," explained Taylor Bell, researcher from the Bay Area Environmental Research Institute and lead author of a study published today in Nature Astronomy. "But we needed more precise measurements from Webb to really begin mapping the temperature, cloud cover, winds, and more detailed atmospheric composition all the way around the planet."

Mapping Temperature and Inferring Weather

Although WASP-43 b is too small, dim, and close to its star for a telescope to see directly, its short orbital period of just 19.5 hours makes it ideal for phase curve spectroscopy, a technique that involves measuring tiny changes in brightness of the star-planet system as the planet orbits the star.

Since the amount of mid-infrared light given off by an object depends largely on how hot it is, the brightness data captured by Webb can then be used to calculate the planet's temperature.

The team used Webb's MIRI (Mid-Infrared Instrument) to measure light from the WASP-43 system every 10 seconds for more than 24 hours. "By observing over an entire orbit, we were able to calculate the temperature of different sides of the planet as they rotate into view," explained Bell. "From that, we could construct a rough map of temperature across the planet."

The measurements show that the dayside has an average temperature of nearly 2,300 degrees Fahrenheit (1,250 degrees Celsius) -- hot enough to forge iron. Meanwhile, the nightside is significantly cooler at 1,100 degrees Fahrenheit (600 degrees Celsius). The data also helps locate the hottest spot on the planet (the "hotspot"), which is shifted slightly eastward from the point that receives the most stellar radiation, where the star is highest in the planet's sky. This shift occurs because of supersonic winds, which move heated air eastward.

"The fact that we can map temperature in this way is a real testament to Webb's sensitivity and stability," said Michael Roman, a co-author from the University of Leicester in the U.K.

To interpret the map, the team used complex 3D atmospheric models like those used to understand weather and climate on Earth. The analysis shows that the nightside is probably covered in a thick, high layer of clouds that prevent some of the infrared light from escaping to space. As a result, the nightside -- while very hot -- looks dimmer and cooler than it would if there were no clouds.

Missing Methane and High Winds

The broad spectrum of mid-infrared light captured by Webb also made it possible to measure the amount of water vapor (H2O) and methane (CH4) around the planet. "Webb has given us an opportunity to figure out exactly which molecules we're seeing and put some limits on the abundances," said Joanna Barstow, a co-author from the Open University in the U.K.

The spectra show clear signs of water vapor on the nightside as well as the dayside of the planet, providing additional information about how thick the clouds are and how high they extend in the atmosphere.

Surprisingly, the data also shows a distinct lack of methane anywhere in the atmosphere. Although the dayside is too hot for methane to exist (most of the carbon should be in the form of carbon monoxide), methane should be stable and detectable on the cooler nightside.

"The fact that we don't see methane tells us that WASP-43b must have wind speeds reaching something like 5,000 miles per hour," explained Barstow. "If winds move gas around from the dayside to the nightside and back again fast enough, there isn't enough time for the expected chemical reactions to produce detectable amounts of methane on the nightside."

The team thinks that because of this wind-driven mixing, the atmospheric chemistry is the same all the way around the planet, which wasn't apparent from past work with Hubble and Spitzer.

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The hidden role of the Milky Way in ancient Egyptian mythology

Ancient Egyptians were known for their religious beliefs and astronomical knowledge of the Sun, Moon, and planets, but up until now it has been unclear what role the Milky Way played in Egyptian religion and culture.

A new study by a University of Portsmouth astrophysicist sheds light on the relationship between the Milky Way and the Egyptian sky-goddess Nut.

Nut is goddess of the sky, who is often depicted as a star-studded woman arched over her brother, the earth god Geb.

She protects the earth from being flooded by the encroaching waters of the void, and plays a key role in the solar cycle, swallowing the Sun as it sets at dusk and giving birth to it once more as it rises at dawn.

The paper draws on ancient Egyptian texts and simulations to argue that the Milky Way might have shone a spotlight, as it were, on Nut's role as the sky.

It proposes that in winter, the Milky Way highlighted Nut's outstretched arms, while in summer, it traced her backbone across the heavens.

Associate Professor in Astrophysics, Dr Or Graur, said: "I chanced upon the sky-goddess Nut when I was writing a book on galaxies and looking into the mythology of the Milky Way. I took my daughters to a museum and they were enchanted by this image of an arched woman and kept asking to hear stories about her.

"This sparked my interest and I decided to combine both astronomy and Egyptology to do a double analysis -- astronomical and cross-cultural -- of the sky-goddess Nut, and whether she really could be linked to the Milky Way."

Dr Graur drew from a rich collection of ancient sources including the Pyramid Texts, Coffin Texts, and the Book of Nut and compared them alongside sophisticated simulations of the Egyptian night sky.

He found compelling evidence that the Milky Way highlighted Nut's divine presence.

Furthermore, Dr Graur connected Egyptian beliefs with those of other cultures, showing similarities in how different societies interpret the Milky Way.

He said: "My study also shows that Nut's role in the transition of the deceased to the afterlife and her connection to the annual bird migration are consistent with how other cultures understand the Milky Way. For example, as a spirits' road among different peoples in North and Central America or as the Birds' Path in Finland and the Baltics.

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Study shedding new light on Earth's global carbon cycle could help assess liveability of other planets

Research has uncovered important new insights into the evolution of oxygen, carbon, and other vital elements over the entire history of Earth – and it could help assess which other planets can develop life, ranging from plants to animals and humans.

The study, published today in Nature Geoscience and led by a researcher at the University of Bristol, reveals for the first time how the build up of carbon-rich rocks has accelerated oxygen production and its release into the atmosphere.

Until now the exact nature of how the atmosphere became oxygen-rich has long eluded scientists and generated conflicting explanations.

As carbon dioxide is steadily emitted by volcanoes, it ends up entering the ocean and forming rocks like limestone.

As global stocks of these rocks build up they can then release their carbon during tectonic processes, including mountain building and metamorphism.

Using this knowledge, the scientists built a unique sophisticated computer model to more accurately chart key changes in the carbon, nutrient and oxygen cycles deep into Earth’s history, over 4 billion years of the planet’s lifetime.

Lead author and biogeochemist Dr Lewis Alcott, Lecturer in Earth Sciences at the University of Bristol, said: “This breakthrough is important and exciting because it may help us understand how planets, other than Earth, have the potential to support intelligent, oxygen-breathing life.

“Previously we didn’t have a clear idea of why oxygen rose from very low concentrations to present-day concentrations, as computer models haven’t previously been able to accurately simulate all the possible feedbacks together. This has puzzled scientists for decades and created different theories.”

The discovery indicates that older planets, originating billions of years ago like Earth, may have better prospects to accumulate enough carbon-rich deposits in their crust, which could facilitate rapid recycling of carbon and nutrients for life.

The findings showed this gradual carbon enrichment of the crust results in ever-increasing recycling rates of carbon and various minerals, including the nutrients needed for photosynthesis, the process green plants use sunlight to absorb nutrients from carbon dioxide and water.

This cycle therefore steadily speeds up oxygen production over the passage of Earth’s history.

The research, which started whilst Dr Alcott was a Hutchinson Postdoctoral Fellow at Yale University in the United States, paves the way for future work to further unravel the complex interrelationships between planetary temperature, oxygen, and nutrients.

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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.

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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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Astronomers reveal a new link between water and planet formation

Researchers have found water vapour in the disc around a young star exactly where planets may be forming. Water is a key ingredient for life on Earth, and is also thought to play a significant role in planet formation. Yet, until now, we had never been able to map how water is distributed in a stable, cool disc -- the type of disc that offers the most favourable conditions for planets to form around stars. The new findings were made possible thanks to the Atacama Large Millimeter/submillimeter Array (ALMA), in which the European Southern Observatory (ESO) is a partner.

"I had never imagined that we could capture an image of oceans of water vapour in the same region where a planet is likely forming," says Stefano Facchini, an astronomer at the University of Milan, Italy, who led the study published today in Nature Astronomy. The observations reveal at least three times as much water as in all of Earth's oceans in the inner disc of the young Sun-like star HL Tauri, located 450 light-years away from Earth in the constellation Taurus.

"It is truly remarkable that we can not only detect but also capture detailed images and spatially resolve water vapour at a distance of 450 light-years from us ," adds co-author Leonardo Testi, an astronomer at the University of Bologna, Italy. The 'spatially resolved' observations with ALMA allow astronomers to determine the distribution of water in different regions of the disc. "Taking part in such an important discovery in the iconic HL Tauri disc was beyond what I had ever expected for my first research experience in astronomy," adds Mathieu Vander Donckt from the University of Liege, Belgium, who was a master's student when he participated in the research.

A significant amount of water was found in the region where a known gap in the HL Tauri disc exists. Ring-shaped gaps are carved out in gas- and dust-rich discs by orbiting young planet-like bodies as they gather up material and grow. "Our recent images reveal a substantial quantity of water vapour at a range of distances from the star that include a gap where a planet could potentially be forming at the present time," says Facchini. This suggests that this water vapour could affect the chemical composition of planets forming in those regions.

Observing water with a ground-based telescope is no mean feat as the abundant water vapour in Earth's atmosphere degrades the astronomical signals. ALMA, operated by ESO together with its international partners, is an array of telescopes in the Chilean Atacama Desert at about 5000 metres elevation that was built in a high and dry environment specifically to minimise this degradation, providing exceptional observing conditions. "To date, ALMA is the only facility able to spatially resolve water in a cool planet-forming disc," says co-author Wouter Vlemmings, a professor at the Chalmers University of Technology in Sweden.*

"It is truly exciting to directly witness, in a picture, water molecules being released from icy dust particles," says Elizabeth Humphreys, an astronomer at ESO who also participated in the study. The dust grains that make up a disc are the seeds of planet formation, colliding and clumping into ever larger bodies orbiting the star. Astronomers believe that where it is cold enough for water to freeze onto dust particles, things stick together more efficiently -- an ideal spot for planet formation. "Our results show how the presence of water may influence the development of a planetary system, just like it did some 4.5 billion years ago in our own Solar System," Facchini adds.

With upgrades happening at ALMA and ESO's Extremely Large Telescope (ELT) coming online within the decade, planet formation and the role water plays in it will become clearer than ever. In particular METIS, the Mid-infrared ELT Imager and Spectrograph, will give astronomers unrivalled views of the inner regions of planet-forming discs, where planets like Earth form.

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Metal scar found on cannibal star

When a star like our Sun reaches the end of its life, it can ingest the surrounding planets and asteroids that were born with it. Now, using the European Southern Observatory's Very Large Telescope (ESO's VLT) in Chile, researchers have found a unique signature of this process for the first time -- a scar imprinted on the surface of a white dwarf star. The results are published today in The Astrophysical Journal Letters.

"It is well known that some white dwarfs -- slowly cooling embers of stars like our Sun -- are cannibalising pieces of their planetary systems. Now we have discovered that the star's magnetic field plays a key role in this process, resulting in a scar on the white dwarf's surface," says Stefano Bagnulo, an astronomer at Armagh Observatory and Planetarium in Northern Ireland, UK, and lead author of the study.

The scar the team observed is a concentration of metals imprinted on the surface of the white dwarf WD 0816-310, the Earth-sized remnant of a star similar to, but somewhat larger than, our Sun.

"We have demonstrated that these metals originate from a planetary fragment as large as or possibly larger than Vesta, which is about 500 kilometres across and the second-largest asteroid in the Solar System," says Jay Farihi, a professor at University College London, UK, and co-author on the study.

The observations also provided clues to how the star got its metal scar.

The team noticed that the strength of the metal detection changed as the star rotated, suggesting that the metals are concentrated on a specific area on the white dwarf's surface, rather than smoothly spread across it. They also found that these changes were synchronised with changes in the white dwarf's magnetic field, indicating that this metal scar is located on one of its magnetic poles.

Put together, these clues indicate that the magnetic field funneled metals onto the star, creating the scar.*

"Surprisingly, the material was not evenly mixed over the surface of the star, as predicted by theory. Instead, this scar is a concentrated patch of planetary material, held in place by the same magnetic field that has guided the infalling fragments," says co-author John Landstreet, a professor at Western University, Canada, who is also affiliated with the Armagh Observatory and Planetarium.

"Nothing like this has been seen before."

To reach these conclusions, the team used a 'Swiss-army knife' instrument on the VLT called FORS2, which allowed them to detect the metal scar and connect it to the star's magnetic field.

"ESO has the unique combination of capabilities needed to observe faint objects such as white dwarfs, and sensitively measure stellar magnetic fields," says Bagnulo.

In their study, the team also relied on archival data from the VLT's X-shooter instrument to confirm their findings.

Harnessing the power of observations like these, astronomers can reveal the bulk composition of exoplanets, planets orbiting other stars outside the Solar System.

This unique study also shows how planetary systems can remain dynamically active, even after 'death'.

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New images reveal what Neptune and Uranus really look like

Neptune is fondly known for being a rich blue and Uranus green -- but a new study has revealed that the two ice giants are actually far closer in colour than typically thought.

The correct shades of the planets have been confirmed with the help of research led by Professor Patrick Irwin from the University of Oxford, which has been published today in the Monthly Notices of the Royal Astronomical Society.

He and his team found that both worlds are in fact a similar shade of greenish blue, despite the commonly-held belief that Neptune is a deep azure and Uranus has a pale cyan appearance.

Astronomers have long known that most modern images of the two planets do not accurately reflect their true colours.

The misconception arose because images captured of both planets during the 20th century -- including by NASA's Voyager 2 mission, the only spacecraft to fly past these worlds -- recorded images in separate colours.

The single-colour images were later recombined to create composite colour images, which were not always accurately balanced to achieve a "true" colour image, and -- particularly in the case of Neptune -- were often made "too blue."

In addition, the early Neptune images from Voyager 2 were strongly contrast enhanced to better reveal the clouds, bands, and winds that shape our modern perspective of Neptune.

Professor Irwin said: "Although the familiar Voyager 2 images of Uranus were published in a form closer to 'true' colour, those of Neptune were, in fact, stretched and enhanced, and therefore made artificially too blue."

"Even though the artificially-saturated colour was known at the time amongst planetary scientists -- and the images were released with captions explaining it -- that distinction had become lost over time."

"Applying our model to the original data, we have been able to reconstitute the most accurate representation yet of the colour of both Neptune and Uranus."

In the new study, the researchers used data from Hubble Space Telescope's Space Telescope Imaging Spectrograph (STIS) and the Multi Unit Spectroscopic Explorer (MUSE) on the European Southern Observatory's Very Large Telescope. In both instruments, each pixel is a continuous spectrum of colours.

This means that STIS and MUSE observations can be unambiguously processed to determine the true apparent colour of Uranus and Neptune.

The researchers used these data to re-balance the composite colour images recorded by the Voyager 2 camera, and also by the Hubble Space Telescope's Wide Field Camera 3 (WFC3).

This revealed that Uranus and Neptune are actually a rather similar shade of greenish blue. The main difference is that Neptune has a slight hint of additional blue, which the model reveals to be due to a thinner haze layer on that planet.

The study also provides an answer to the long-standing mystery of why Uranus's colour changes slightly during its 84-year orbit of the Sun.

The authors came to their conclusion after first comparing images of the ice giant to measurements of its brightness, which were recorded by the Lowell Observatory in Arizona from 1950 -- 2016 at blue and green wavelengths.

These measurements showed that Uranus appears a little greener at its solstices (i.e. summer and winter), when one of the planet's poles is pointed towards our star. But during its equinoxes -- when the Sun is over the equator -- it has a somewhat bluer tinge.

Part of the reason for this was known to be because Uranus has a highly unusual spin.

It effectively spins almost on its side during its orbit, meaning that during the planet's solstices either its north or south pole points almost directly towards the Sun and Earth.

This is important, the authors said, because any changes to the reflectivity of the polar regions would therefore have a big impact on Uranus's overall brightness when viewed from our planet.

What astronomers were less clear about is how or why this reflectivity differs.

This led the researchers to develop a model which compared the spectra of Uranus's polar regions to its equatorial regions.

It found that the polar regions are more reflective at green and red wavelengths than at blue wavelengths, partly because methane, which is red absorbing, is about half as abundant near the poles than the equator.

However, this wasn't enough to fully explain the colour change so the researchers added a new variable to the model in the form of a 'hood' of gradually thickening icy haze which has previously been observed over the summer, sunlit pole as the planet moves from equinox to solstice.

Astronomers think this is likely to be made up of methane ice particles.

When simulated in the model, the ice particles further increased the reflection at green and red wavelengths at the poles, offering an explanation as to why Uranus is greener at the solstice.

Professor Irwin said: "This is the first study to match a quantitative model to imaging data to explain why the colour of Uranus changes during its orbit."

"In this way, we have demonstrated that Uranus is greener at the solstice due to the polar regions having reduced methane abundance but also an increased thickness of brightly scattering methane ice particles."

Dr Heidi Hammel, of the Association of Universities for Research in Astronomy (AURA), who has spent decades studying Neptune and Uranus but was not involved in the study, said: "The misperception of Neptune's colour, as well as the unusual colour changes of Uranus, have bedevilled us for decades. This comprehensive study should finally put both issues to rest."

The ice giants Uranus and Neptune remain a tantalising destination for future robotic explorers, building on the legacy of Voyager in the 1980s.

Professor Leigh Fletcher, a planetary scientist from the University of Leicester and co-author of the new study, said: "A mission to explore the Uranian system -- from its bizarre seasonal atmosphere, to its diverse collection of rings and moons -- is a high priority for the space agencies in the decades to come."

However, even a long-lived planetary explorer, in orbit around Uranus, would only capture a short snapshot of a Uranian year.

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Sodium's high-pressure transformation can tell us about the interiors of stars, planets

Travel deep enough below Earth's surface or inside the center of the Sun, and matter changes on an atomic level.

The mounting pressure within stars and planets can cause metals to become nonconducting insulators.

Sodium has been shown to transform from a shiny, gray-colored metal into a transparent, glass-like insulator when squeezed hard enough.

Now, a University at Buffalo-led study has revealed the chemical bonding behind this particular high-pressure phenomenon.

While it's been theorized that high pressure essentially squeezes sodium's electrons out into the spaces between atoms, researchers' quantum chemical calculations show that these electrons still very much belong to the surrounding atoms and are chemically bonded to each other.

"We're answering a very simple question of why sodium becomes an insulator, but predicting how other elements and chemical compounds behave at very high pressures will potentially give insight into bigger-picture questions," says Eva Zurek, Ph.D., professor of chemistry in the UB College of Arts and Sciences and co-author of the study, which was published in Angewandte Chemie, a journal of the German Chemical Society.

"What's the interior of a star like? How are planets' magnetic fields generated, if indeed any exist? And how do stars and planets evolve? This type of research moves us closer to answering these questions."

The study confirms and builds upon the theoretical predictions of the late renowned physicist Neil Ashcroft, whose memory the study is dedicated to.

It was once thought that materials always become metallic under high pressure -- like the metallic hydrogen theorized to make up Jupiter's core -- but Ashcroft and Jeffrey Neaton's seminal paper two decades ago found some materials, like sodium, can actually become insulators or semiconductors when squeezed.

They theorized that sodium's core electrons, thought to be inert, would interact with each other and the outer valence electrons when under extreme pressure.

"Our work now goes beyond the physics picture painted by Ashcroft and Neaton, connecting it with chemical concepts of bonding," says the UB-led study's lead author, Stefano Racioppi, Ph.D., a postdoctoral researcher in the UB Department of Chemistry.

Pressures found below Earth's crust can be difficult to replicate in a lab, so using supercomputers in UB's Center for Computational Research, the team ran calculations on how electrons behave in sodium atoms when under high pressure.

The electrons become trapped within the interspatial regions between atoms, known as an electride state.

This causes sodium's physical transformation from shiny metal to transparent insulator, as free-flowing electrons absorb and retransmit light but trapped electrons simply allow the light to pass through.

However, researchers' calculations showed for the first time that the emergence of the electride state can be explained through chemical bonding.

The high pressure causes electrons to occupy new orbitals within their respective atoms.

These orbitals then overlap with each other to form chemical bonds, causing localized charge concentrations in the interstitial regions.

While previous studies offered an intuitive theory that high pressure squeezed electrons out of atoms, the new calculations found that the electrons are still part of surrounding atoms.

"We realized that these are not just isolated electrons that decided to leave the atoms. Instead, the electrons are shared between the atoms in a chemical bond," Racioppi says.

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An astronomical waltz reveals a sextuplet of planets

An international collaboration between astronomers using the CHEOPS and TESS space satellites, including NCCR PlanetS members from the University of Bern and the University of Geneva, have found a key new system of six transiting planets orbiting a bright star in a harmonic rhythm. This rare property enabled the team to determine the planetary orbits which initially appeared as an unsolvable riddle.

CHEOPS is a joint mission by ESA and Switzerland, under the leadership of the University of Bern in collaboration with the University of Geneva. Thanks to a collaboration with scientists working with data from NASA's satellite TESS, the international team could uncover the planetary system orbiting the nearby star HD110067. A very distinctive feature of this system is its chain of resonances: the planets orbit their host star in perfect harmony. Part of the research team are researchers from the University of Bern and the University of Geneva who are also members of the National Center of Competence in Research (NCCR) PlanetS. The findings have just been published in Nature.

The planets in the HD110067 system revolve around the star in a very precise waltz. When the closest planet to the star makes three full revolutions around it, the second one makes exactly two during the same time. This is called a 3:2 resonance. "Amongst the over 5000 exoplanets discovered orbiting other stars than our Sun, resonances are not rare, nor are systems with several planets. What is extremely rare though, is to find systems where the resonances span such a long chain of six planets" points out Dr. Hugh Osborn, CHEOPS fellow at the University of Bern, leader of CHEOPS observation programme involved in the study, and co-author of the publication. This is precisely the case of HD110067 whose planets form a so-called "resonant chain" in successive pairs of 3:2, 3:2, 3:2, 4:3, and 4:3 resonances, resulting in the closest planet completing six orbits while the outer-most planet does one.

A seemingly unsolvable puzzle

Although multiple planets were initially detected thanks to their transits, the exact arrangement of the planets was unclear at first. However, the precise gravitational dance enabled the scientists' team to solve the puzzle of HD110067. Prof. Adrien Leleu from the University of Geneva, in charge of analysing the orbital resonances, and co-author of the study, explains: "A transit occurs when a planet, from our point of view, passes in front of its host star, blocking a minute fraction of the starlight, creating an apparent dip of its brightness." From the first observations carried out by NASA's TESS satellite, it was possible to determine that the two inner planets called 'b' and 'c' have orbital periods of 9 and 14 days respectively. However, no conclusions could be drawn for the other four detected planets as two were seen to transit once in 2020 and once in 2022 with a large 2-year gap in the data, and the other two transited only once in 2022.

The solution to the puzzle for those four additional planets finally began to emerge thanks to observations with the CHEOPS space telescope. While TESS aims at scanning all of the sky bit by bit to find short-period exoplanets, CHEOPS is a targeted mission, focusing on a single star at a time with exquisite precision. "Our CHEOPS observations enabled us to find that the period of planet 'd' is 20.5 days. Also, it ruled out multiple possibilities for the remaining three outer planets, 'e', 'f' and 'g'," reveals Osborn.

Predicting the precise waltz of the planets

That is when the team realized that the three inner planets of HD110067 are dancing in a precise 3:2, 3:2 chain of resonances: when the innermost planet revolves nine times around the star, the second revolves six times and the third planet four times.

The team then considered the possibility that the three other planets could also be part of the chain of resonances. "This led to dozens of possibilities for their orbital period," explains Leleu, "but combining existing observational data from TESS and CHEOPS, with our model of the gravitational interactions between the planets, we could exclude all solutions but one: the 3:2, 3:2, 3:2, 4:3, 4:3 chain." The scientists could therefore predict that the outer three planets ('e', 'f' and 'g') have orbital periods of 31, 41 days, and 55 days.

This prediction allowed to schedule observations with a variety of ground-based telescopes. Further transits of planet 'f' were observed, revealing it was precisely where theory predicted it based on the resonant-chain. Finally, reanalysis of the data from TESS revealed two hidden transits, one from each of planets 'f' and 'g', exactly at the times expected by the predictions, confirming the periods of the six planets. Additional CHEOPS observations of each planet, and in particular planet 'e' are scheduled in the near future.

A key system for the future

From the handful of resonant-chain systems found so far, CHEOPS has highly contributed to the understanding of not only HD110067, but also of TOI-178. Another well-known example of a resonant-chain system is the TRAPPIST-1 system which hosts seven rocky planets. However, TRAPPIST-1 is a small and incredibly faint star which makes any additional observations very difficult. HD110067, on the other hand, is more than 50 times brighter than TRAPPIST-1.

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'Bouncing' comets could deliver building blocks for life to exoplanets

How did the molecular building blocks for life end up on Earth? One long-standing theory is that they could have been delivered by comets. Now, researchers from the University of Cambridge have shown how comets could deposit similar building blocks to other planets in the galaxy.

In order to deliver organic material, comets need to be travelling relatively slowly -- at speeds below 15 kilometres per second. At higher speeds, the essential molecules would not survive -- the speed and temperature of impact would cause them to break apart.

The most likely place where comets can travel at the right speed are 'peas in a pod' systems, where a group of planets orbit closely together. In such a system, the comet could essentially be passed or 'bounced' from the orbit of one planet to another, slowing it down.

At slow enough speeds, the comet would crash on a planet's surface, delivering the intact molecules that researchers believe are the precursors for life. The results, reported in the Proceedings of the Royal Society A, suggest that such systems would be promising places to search for life outside our Solar System if cometary delivery is important for the origins of life.

Comets are known to contain a range of the building blocks for life, known as prebiotic molecules. For example, samples from the Ryugu asteroid, analysed in 2022, showed that it carried intact amino acids and vitamin B3. Comets also contain large amounts of hydrogen cyanide (HCN), another important prebiotic molecule. The strong carbon-nitrogen bonds of HCN make it more durable to high temperatures, meaning it could potentially survive atmospheric entry and remain intact.

"We're learning more about the atmospheres of exoplanets all the time, so we wanted to see if there are planets where complex molecules could also be delivered by comets," said first author Richard Anslow from Cambridge's Institute of Astronomy. "It's possible that the molecules that led to life on Earth came from comets, so the same could be true for planets elsewhere in the galaxy."

The researchers do not claim that comets are necessary to the origin of life on Earth or any other planet, but instead they wanted to place some limits on the types of planets where complex molecules, such as HCN, could be successfully delivered by comets.

Most of the comets in our Solar System sit beyond the orbit of Neptune, in what is known as the Kuiper Belt. When comets or other Kuiper Belt objects (KBOs) collide, they can be pushed by Neptune's gravity toward the Sun, eventually getting pulled in by Jupiter's gravity. Some of these comets make their way past the Asteroid Belt and into the inner Solar System.

"We wanted to test our theories on planets that are similar to our own, as Earth is currently our only example of a planet that supports life," said Anslow. "What kinds of comets, travelling at what kinds of speed, could deliver intact prebiotic molecules?"

Using a variety of mathematical modelling techniques, the researchers determined that it is possible for comets to deliver the precursor molecules for life, but only in certain scenarios. For planets orbiting a star similar to our own Sun, the planet needs to be low mass and it is helpful for the planet to be in close orbit to other planets in the system. The researchers found that nearby planets on close orbits are much more important for planets around lower-mass stars, where the typical speeds are much higher.

In such a system, a comet could be pulled in by the gravitational pull of one planet, then passed to another planet before impact. If this 'comet-passing' happened enough times, the comet would slow down enough so that some prebiotic molecules could survive atmospheric entry.

"In these tightly-packed systems, each planet has a chance to interact with and trap a comet," said Anslow. "It's possible that this mechanism could be how prebiotic molecules end up on planets."

For planets in orbit around lower-mass stars, such as M-dwarfs, it would be more difficult for complex molecules to be delivered by comets, especially if the planets are loosely packed. Rocky planets in these systems also suffer significantly more high-velocity impacts, potentially posing unique challenges for life on these planets.

The researchers say their results could be useful when determining where to look for life outside the Solar System.

"It's exciting that we can start identifying the type of systems we can use to test different origin scenarios," said Anslow. "It's a different way to look at the great work that's already been done on Earth. What molecular pathways led to the enormous variety of life we see around us? Are there other planets where the same pathways exist? It's an exciting time, being able to combine advances in astronomy and chemistry to study some of the most fundamental questions of all."

Read more at Science Daily

Researchers capture first-ever afterglow of huge planetary collision in outer space

The study, published today in Nature, reports the sighting of two ice giant exoplanets colliding around a sun-like star, creating a blaze of light and plumes of dust. Its findings show the bright heat afterglow and resulting dust cloud, which moved in front of the parent star dimming it over time.

The international team of astronomers was formed after an enthusiast viewed the light curve of the star and noticed something strange. It showed the system doubled in brightness at infrared wavelengths some three years before the star started to fade in visible light.

Co-lead author Dr Matthew Kenworthy, from Leiden University, said: "To be honest, this observation was a complete surprise to me. When we originally shared the visible light curve of this star with other astronomers, we started watching it with a network of other telescopes.

"An astronomer on social media pointed out that the star brightened up in the infrared over a thousand days before the optical fading. I knew then this was an unusual event."

The network of professional and amateur astronomers studied the star intensively including monitoring changes in the star's brightness over the next two years. The star was named ASASSN-21qj after the network of telescopes that first detected the fading of the star at visible wavelengths.

The researchers concluded the most likely explanation is that two ice giant exoplanets collided, producing the infrared glow detected by NASA's NEOWISE mission, which uses a space telescope to hunt for asteroids and comets.

Co-lead author Dr Simon Lock, Research Fellow in Earth Sciences at the University of Bristol, said: "Our calculations and computer models indicate the temperature and size of the glowing material, as well as the amount of time the glow has lasted, is consistent with the collision of two ice giant exoplanets."

The resultant expanding debris cloud from the impact then travelled in front of the star some three years later, causing the star to dim in brightness at visible wavelengths.

Over the next few years, the cloud of dust is expected to start smearing out along the orbit of the collision remnant, and a tell-tale scattering of light from this cloud could be detected with both ground-based telescopes and NASA's largest telescope in space, known as JWST.

The astronomers plan on watching closely what happens next in this system.

Read more at Science Daily

Hot Jupiter blows its top

A planet about 950 light years from Earth could be the Looney Tunes' Yosemite Sam equivalent of planets, blowing its atmospheric 'top' in spectacular fashion.

The planet called HAT-P-32b is losing so much of its atmospheric helium that the trailing gas tails are among the largest structures yet known of an exoplanet, a planet outside our solar system, according to observations by astronomers.

Three-dimensional (3D) simulations on the Stampede2 supercomputer of the Texas Advanced Computing Center (TACC) helped model the flow of the planet's atmosphere, based on data from the Hobby-Eberly Telescope of The University of Texas at Austin's McDonald Observatory. The scientists hope to widen their planet-observing net and survey 20 additional star systems to find more planets losing their atmosphere and learn about their evolution.

"We have monitored this planet and the host star with long time series spectroscopy, observations made of the star and planet over a couple of nights. And what we found is there's a gigantic helium gas tail that is associated with the planet. The tail is large -- about 53 times the planet's radius -- formed by gas that's escaping from the planet," said Zhoujian Zhang, a postdoctoral fellow in the Department of Astronomy & Astrophysics, University of California Santa Cruz.

Zhang is the lead author in a study on the helium tail detected from HAT-P 32b that was published in Science Advances June 2023. The science team used data from the Habitable Planet Finder spectrograph, an instrument on the Hobby-Eberly telescope, which provides high spectral resolution of light in near infrared wavelengths.

The planet HAT-P-32b was discovered in 2011 using spectroscopic data from the Hungarian-made Automated Telescope Network. It's known as a 'hot Jupiter,' a gas giant similar to our neighboring planet Jupiter, but with a radius twice as large. This hot Jupiter hugs closely in orbit to its host star, about three percent the distance from the Earth to the Sun. Its orbital period -- what we consider a year here on Earth -- is only 2.15 days, and this proximity to the star scorches it with both long and short wave radiation.

The main motivation for the scientists' interest in studying hot Jupiters is their pursuit of the mystery of the Neptunian desert, the inexplicable relative scarcity on average of intermediate-mass planets, or sub-Jupiters, with short orbital periods.

"One of the potential explanations is that maybe the planets are losing their mass," Zhang offered. "If we can capture planets in the process of losing their atmosphere, then we can study how fast the planet is losing their mass and what are the mechanisms that cause their atmosphere to escape from the planet. It's good to have some examples to see like the HAT-P-32b process in action."

The light analyzed in the study comes from the star HAT-P-32 A. It's slightly hotter and similar in size to our own sun. The analyzed light is not just straight starlight. As the planet passes in front of the star, for just a couple of hours the starlight gets filtered the most by the planet's gassy atmosphere. This filtering, called absorption, reveals features of the transiting planet, in this case huge outflows of helium when the spectra were analyzed.

Zhang and colleagues used a technique called transmission spectroscopy to separate the starlight into its component frequencies, like a prism separates sunlight into a rainbow spectrum. Gaps in the spectrum indicate light being absorbed by elements in the gaseous atmosphere of HAT-P-32b.

"What we see in our data is that when the planet is transiting the star, we see there's deeper helium absorption lines. The helium absorption is stronger than what we expect from the stellar atmosphere. This excess helium absorption should be caused by the planet's atmosphere. When the planet is transiting, its atmosphere is so huge that it blocks part of the atmosphere that absorbs the helium line, and that causes this excess absorption. That's how we discovered the HAT-P-32b to be an interesting planet," Zhang said.

It got more interesting as they developed 3D hydrodynamical simulations of the HAT-P-32b and host star, led by Antonija Oklopčić, Anton Pannekoek Institute for Astronomy, University of Amsterdam; and Morgan MacLeod, Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, Harvard University.

The models examined the interactions between the planetary outflow and stellar winds in the tidal gravitational field of the extrasolar system. The models showed columnar tails of planetary outflow both leading and trailing the planet along its orbital path with excess helium absorption even far from the transit points that matched observations. What is more, the models suggest complete loss of the atmosphere in about 4 x 10e10 Earth years.

"We made use of TACC's Stampede2 system's Intel Skylake nodes for our calculations," MacLeod said. "This computation involves tracking flow as it accelerates from a slow-moving subsonic 'atmosphere' near the planet to a supersonic wind as it moves further away. The HAT-P-32b system was identified to have a large-scale outflow similar in size to the planet's orbit around the star. Taken together, these requirements suggest the need for a stable, high-accuracy algorithm for solving three-dimensional gas dynamics."

The modelers utilized the Athena++ hydrodynamic software and a custom problem setup to do their calculation on Stampede2. With it they solve the equations of gas dynamics in a rotating frame of reference that matches the planet's orbital motion. Athena++ is a Eulerian code -- the flow is discretized with volume elements -- and they used nested layers of mesh refinement to capture the large-scale star-planet system along with the much smaller scale of the atmosphere near the planet's surface.

"Using the TACC HPC systems is a joy," MacLeod said. "A few things go into this -- the first, and most important is the level of support. Whenever I have a problem, I can call the support line, get help, and get back to doing the science that I am best at. Secondly, the vast majority of my time goes into developing and validating model results, rather than running a single, full-scale calculation. The TACC systems are incredibly well set up for this reality, and it hugely speeds up the pace of development. Being able to run test calculations through the development queues or submit larger calculations of a range of sizes in the lead up to an eventual final model is crucial and effective in these environments."

Looking ahead, the scientists hope to continue to develop sophisticated 3D models that capture effects such as atmospheric mixing of gases and even winds within the atmosphere on more distant worlds hundreds and even thousands of light years away.

"Now is the time to have supercomputers with the computational power to make this happen," Zhang said. "We need the computers to make real predictions based on recent advances in the theory and to explain the data. Supercomputers bridge the model and the data."

Read more at Science Daily

Want to know how light works? Try asking a mechanic

Since the 17th century, when Isaac Newton and Christiaan Huygens first debated the nature of light, scientists have been puzzling over whether light is best viewed as a wave or a particle -- or perhaps, at the quantum level, even both at once. Now, researchers at Stevens Institute of Technology have revealed a new connection between the two perspectives, using a 350-year-old mechanical theorem -- ordinarily used to describe the movement of large, physical objects like pendulums and planets -- to explain some of the most complex behaviors of light waves.

The work, led by Xiaofeng Qian, assistant professor of physics at Stevens and reported in the August 17 online issueof Physical Review Research, also proves for the first time that a light wave's degree of non-quantum entanglement exists in a direct and complementary relationship with its degree of polarization. As one rises, the other falls, enabling the level of entanglement to be inferred directly from the level of polarization, and vice versa. This means that hard-to-measure optical properties such as amplitudes, phases and correlations -- perhaps even these of quantum wave systems -- can be deduced from something a lot easier to measure: light intensity.

"We've known for over a century that light sometimes behaves like a wave, and sometimes like a particle, but reconciling those two frameworks has proven extremely difficult," said Qian "Our work doesn't solve that problem -- but it does show that there are profound connections between wave and particle concepts not just at the quantum level, but at the level of classical light-waves and point-mass systems."

Qian's team used a mechanical theorem, originally developed by Huygens in a 1673 book on pendulums, that explains how the energy required to rotate an object varies depending on the object's mass and the axis around which it turns. "This is a well-established mechanical theorem that explains the workings of physical systems like clocks or prosthetic limbs," Qian explained. "But we were able to show that it can offer new insights into how light works, too."

This 350-year-old theorem describes relationships between masses and their rotational momentum, so how could it be applied to light where there is no mass to measure? Qian's team interpreted the intensity of a light as the equivalent of a physical object's mass, then mapped those measurements onto a coordinate system that could be interpreted using Huygens' mechanical theorem. "Essentially, we found a way to translate an optical system so we could visualize it as a mechanical system, then describe it using well-established physical equations," explained Qian.

Once the team visualized a light wave as part of a mechanical system, new connections between the wave's properties immediately became apparent -- including the fact that entanglement and polarization stood in a clear relationship with one another.

"This was something that hadn't been shown before, but that becomes very clear once you map light's properties onto a mechanical system," said Qian. "What was once abstract becomes concrete: using mechanical equations, you can literally measure the distance between 'center of mass' and other mechanical points to show how different properties of light relate to one another."

Clarifying these relationships could have important practical implications, allowing subtle and hard-to-measure properties of optical systems -- or even quantum systems -- to be deduced from simpler and more robust measurements of light intensity, Qian explained. More speculatively, the team's findings suggest the possibility of using mechanical systems to simulate and better-understand the strange and complex behaviors of quantum wave systems.

Read more at Science Daily

New exoplanet discovery builds better understanding of planet formation

An international team of scientists have discovered an unusual Jupiter-sized planet orbiting a low-mass star called TOI-4860, located in the Corvus constellation.

The newly discovered gas giant, named TOI-4860 b, is an unusual planet for two reasons: stars of such low mass are not expected to host planets like Jupiter, and the planet appears to be particularly enriched by heavy elements.

The study, led by University of Birmingham astronomers, is published today (Friday 4th August) in a letter published within the Monthly Notices of the Royal Astronomical Society.

The planet was initially identified using NASA's Transiting Exoplanet Survey Satellite as a drop of brightness while transiting in front of its host star, but that data alone was insufficient to confirm that it was a planet.

The team used the SPECULOOS South Observatory, located in the Atacama Desert in Chile, to measure the planetary signal in several wavelengths and validated the planetary nature. The astronomers also observed the planet just before and after it disappeared behind its host star, noticing that there was no change in light, meaning the planet was not emitting any. Finally, the team collaborated with a Japanese group using the Subaru Telescope in Hawai'i. Together they measured the mass of the planet to fully confirm it.

Following this star and confirming its planet was the initiative of a group of PhD students within the SPECULOOS project.

George Dransfield, one of those PhD students, who recently submitted her thesis at the University of Birmingham, explains: "Under the canonical planet formation model, the less mass a star has, the less massive is the disc of material around that star.

"Since planets are created from that disc, high-mass planets like Jupiter, were widely expected not to form. However, we were curious about this and wanted to check planetary candidates to see if it was possible. TOI-4860 is our first confirmation and also the lowest mass star hosting such a high mass planet."

Amaury Triaud, Professor of Exoplanetology at the University of Birmingham, who led the study said: "I am ever thankful to the bright PhD students of our team for proposing to observe systems like TOI-4860. Their work has really paid off since planets like TOI-4860 are vital to deepening our understanding of planet formation.

"A hint of what might have happened is hidden in the planetary properties, which appear particularly enriched in heavy elements. We have detected something similar in the host star too, so it is likely that an abundance of heavy elements catalysed the planet formation process."

The new gas giant takes about 1.52 days to complete a full orbit around its host star, but because its host is a cold low mass star, the planet itself can be referred to as a 'Warm Jupiter'. This is a subclass of planet that holds particular interest for astronomers looking to build on their initial observations and learn more about how these kinds of planets are formed.

Mathilde Timmermans, another student of the SPECULOOS project, working at the University of Liege in Belgium concludes: "Thanks to its very short orbital period, and to the properties of its host star, the discovery of TOI-4860 b provides a brilliant opportunity to study the atmospheric properties of a warm Jupiter and learn more about how gas giants are formed."

Read more at Science Daily

Dune patterns reveal environmental change on Earth and other planets

Dunes, the mounds of sand formed by the wind that vary from ripples on the beach to towering behemoths in the desert, are incarnations of surface processes, climate change, and the surrounding atmosphere. For decades, scientists have puzzled over why they form different patterns.

Now, Stanford researchers have found a way to interpret the meaning of these patterns. Their results, published in Geology Aug. 1, can be used as a new tool for understanding environmental changes on any planetary body that harbors dunes, including Venus, Earth, Mars, Titan, Io, and Pluto.

"When you look at other planets, all you have is pictures taken from hundreds to thousands of kilometers away from the surface. You can see dunes -- but that's it. You don't have access to the surface," said senior study author Mathieu Lapôtre, an assistant professor of Earth and planetary sciences in the Stanford Doerr School of Sustainability. "These findings offer a really exciting new tool to decipher the environmental history of these other planets where we have no data."

The scientists analyzed satellite images of 46 dune fields on Earth and Mars and studied how the dunes interact, or exchange sand. Physically, dune interactions manifest themselves as locations where the crestlines of two dunes get very close to each other. Through such interactions, dunes evolve toward a pattern that is free of defects, reflecting a state of equilibrium with local conditions. Thus, the researchers hypothesized that a high number of interactions, in turn, must signal recent or local changes in those boundary conditions. To test their hypothesis, they used data from Earth and Mars to verify how known changes in environmental conditions, such as wind direction or the amount of sand available, affected dune interactions in the dune fields.

Finding a pattern

In a part of China's Tengger Desert, researchers once flattened a dune field to have a baseline for understanding its subsequent reformation. The study authors analyzed satellite images of the dune field from 2016 to 2022 to see how it grew from a flat bed to large dunes in equilibrium with their environment.

"When the dunes and their patterns were not in equilibrium with their current conditions, the interaction density was high, and through time we could see it decreased consistently, as is expected from our hypothesis," Lapôtre said.

Next, they investigated dunes migrating through a valley in the Namib Desert to see how changes in the wind conditions, triggered by topography, impacted dune patterns. They found that dunes outside the valley displayed few defects in their patterns, but as they migrated through the valley -- which starts very wide, then narrows, then becomes wide again -- dunes interacted more with each other.

"As both sand and winds get funneled into the valley, the dunes feel a change in their boundary conditions, and their pattern needs to adjust," said lead study author Colin Marvin, a PhD student in Earth and planetary sciences. "They move into the portion outside the valley and they again readjust to their unconfined conditions, and we see a drop in the number of interactions. This trend is exactly what we expected to see."

They also found that pattern to be true on Mars, where a big dune field occurs around the north pole. There, the migrating dunes have settled into their current conditions -- they're well spaced, they look the same, they're the same size -- and because of that, they interact very little with one another. But further downwind, the winds become more variable and frost locally makes it harder for grains to be blown away. There, the dunes react to that change until they have migrated far enough into these new conditions for their pattern to have once again matured, decreasing the number of dune interactions.

Testing the tool

"We have an upper bound on the time that it takes for a given dune to adjust to changes in environmental conditions, and that is the time it takes for a dune to migrate by a distance of one dune length," Marvin said. "We can use this to diagnose recent changes in environmental conditions on planetary bodies where we don't have any information other than images taken from orbit or radar for example."

Understanding the recent climate of Mars by analyzing current dune patterns could possibly help scientists better pinpoint, for example, the latitudes and depth where future astronauts might be able to find water ice in the subsurface, Lapôtre added. The study also informs experts about the mechanics of dunes on Earth, which can help them better interpret Earth's rock record, and thus, our planet's distant past. On Saturn's moon Titan, this approach could reveal information about topography around the equator and tropics, which is near where the Dragonfly Mission is going to land in the mid 2030s.

"Topography can tell you about a lot of different things; for example, the geological history of the planet: Does Titan have tectonics? How does the interior of Titan work, and how is it coupled with the surface? Is there significant erosion?" Lapôtre said. "Interpretations of dune patterns could trigger kind of a chain reaction, where you provide a new constraint, and it's going to be useful to a bunch of people to make a bunch of discoveries down the line."

Because other planets have various sizes, gravities, temperatures, and compositions, their geological processes will differ. Compared with a rover that lands on one point of a planet to collect information, the satellite data of entire dune fields can greatly increase scientists' understanding of these extraterrestrial bodies and how they can inform our understanding of Earth.

"If we want to understand what happened in the past, or if we want to predict what will happen in the future, it's hard to do when all you have to create those models is one data point, or just one planet," Lapôtre said. "Ultimately, this kind of information allows us to make much better interpretations of Earth's past and also predictions of Earth's future."

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New planetary formation findings

Rochester Institute of Technology's Joel Kastner, a professor in the Chester F. Carlson Center for Imaging Science and School of Physics and Astronomy, and a team of researchers with the European Southern Observatory (ESO) have discovered new evidence of how planets as massive as Jupiter can form, using images from the ESO's Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA).

The combination of VLT and ALMA imaging have yielded detections of dusty clumps close to the young star V960 Mon that could collapse to create giant planets. The work is based on an infrared image obtained with the Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE) instrument on ESO's VLT and a radio-wavelength image with ALMA that together reveal, in fascinating detail, the material around the star.

This young star attracted astronomers' attention when it suddenly increased its brightness more than 20 times in 2014. SPHERE observations taken shortly after the onset of this brightness "outburst" revealed that the material orbiting V960 Mon is assembling together in a series of intricate spiral arms extending over distances bigger than the entire solar system.

Kastner worked on the SPHERE imaging project with former RIT student David Principe '14 Ph.D. (astrophysical sciences and technology), who is now at the Kavli Institute for Astrophysics and Space Research at the Massachusetts Institute of Technology.

"The two of us put SPHERE observing proposals together to look at these outbursting objects," said Kastner. "We were hoping to see structure around them that is lit up by the outbursts, but we really weren't sure what kind of structure we might see. We thought we might be able to see the dusty material around the star that is feeding the star and maybe forming planets, and this was a great case where both appear to have been detected."

Astronomers believe that giant planets form either by "core accretion,"' when dust grains slowly coagulate to form a massive core that sweeps up gas, or by "gravitational instability," when large fragments of the material around a star quickly contract and collapse. While researchers have previously found evidence for the first of these scenarios, support for the latter has been scant. The images from VLT now show a real observation of gravitational instability happening at planetary scales.

"It's a confirmation that one of the basic ideas of how planets form works," said Kastner. "It's a pretty good demonstration of what has been shown in very detailed simulations of discs around young stars to determine if they are making planets."

The research team presented its findings in the July 25 issue of The Astrophysical Journal Letters. Authors span across the globe while the VLT and ALMA are located in Chile's Atacama Desert.

The ESO enables scientists worldwide to discover the secrets of the universe for the benefit of all. Established as an intergovernmental organization in 1962, today ESO is supported by 16 member states (Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland, and the United Kingdom), along with the host state of Chile and with Australia as a strategic partner.

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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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