ST/ Mysterious ‘blue blobs’ reveal a new kind of star system

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Paradigm

36 min readJun 22, 2022

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Space biweekly vol.54, 8th June — 22th June

TL;DR

Astronomers identify a new class of stellar system. They’re not quite galaxies and only exist in isolation.
A new study of an old meteorite contradicts current thinking about how rocky planets like the Earth and Mars acquire volatile elements such as hydrogen, carbon, oxygen, nitrogen and noble gases as they form.
Astronomers have imaged the debris disk of the nearby star HD 53143 at millimeter wavelengths for the first time, and it looks nothing like they expected. Based on early coronagraphic data, scientists expected ALMA to confirm the debris disk as a face-on ring peppered with clumps of dust. Instead, the observations took a surprise turn, revealing the most complicated and eccentric debris disk observed to date.
Space scientists have discovered a ‘super Jupiter’ orbiting a white dwarf, detected using direct observations with the European Space Agency (ESA)’s Gaia mission.
Scientists have observed a significant amount of cold, neutral gas in the outer regions of the young galaxy A1689-zD1, as well as outflows of hot gas coming from the galaxy’s center. These results may shed light on a critical stage of galactic evolution for early galaxies, where young galaxies begin the transformation to be increasingly like their later, more structured cousins.
Astronomers have mapped the surface properties of the asteroid Psyche, revealing a landscape of metal and rock.
A research team has observed the fastest nova ever. They hope to find answers to not only the nova’s many baffling traits, but to larger questions about our solar system and the universe.
Finding forming planets is a tough but important job for astronomers: Only three planets have ever been discovered caught in the process of forming, and the most recent of these was found just weeks ago.
Astronomers have unveiled intricate details of the star-forming region 30 Doradus, also known as the Tarantula Nebula, using new observations from the Atacama Large Millimeter/submillimeter Array (ALMA). Now we can see the nebula in a new light, with wispy gas clouds that provide insight into how massive stars shape this region.
Astronomers using a fleet of world leading telescopes on the ground and in space have captured images of a periodic rocky near-Sun comet breaking apart. This is the first time such a comet has been caught in the act of disintegrating and could help explain the scarcity of such periodic near-Sun comets.
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Analysts at Morgan Stanley and Goldman Sachs have predicted that economic activity in space will become a multi-trillion-dollar market in the coming decades. Morgan Stanley’s Space Team estimates that the roughly USD 350 billion global space industry could surge to over USD 1 trillion by 2040.

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Young, blue, and isolated stellar systems in the Virgo Cluster. II. A new class of stellar system

by Michael G. Jones, David J. Sand, Michele Bellazzini, et al, submitted to The Astrophysical Journal

University of Arizona astronomers have identified five examples of a new class of stellar system. They’re not quite galaxies and only exist in isolation.

The new stellar systems contain only young, blue stars, which are distributed in an irregular pattern and seem to exist in surprising isolation from any potential parent galaxy. The stellar systems — which astronomers say appear through a telescope as “blue blobs” and are about the size of tiny dwarf galaxies — are located within the relatively nearby Virgo galaxy cluster. The five systems are separated from any potential parent galaxies by over 300,000 light years in some cases, making it challenging to identify their origins.

Locations of BCs (and SECCO 1) in the direction of Virgo overlaid on a ROSAT mosaic of hard (0.4–2.4 keV) X-ray emission (Brown et al. 2021).

The astronomers found the new systems after another research group, led by the Netherlands Institute for Radio Astronomy’s Elizabeth Adams, compiled a catalog of nearby gas clouds, providing a list of potential sites of new galaxies. Once that catalog was published, several research groups, including one led by UArizona associate astronomy professor David Sand, started looking for stars that could be associated with those gas clouds.

The gas clouds were thought to be associated with our own galaxy, and most of them probably are, but when the first collection of stars, called SECCO1, was discovered, astronomers realized that it was not near the Milky Way at all, but rather in the Virgo cluster, which is much farther away but still very nearby in the scale of the universe.

Top-left: False color HST F606W+F814W image of BC1. The dashed green circle shows the region used to construct the CMD. At the distance of the Virgo cluster (16.5 Mpc) 2000 is 1.6 kpc. Top-right: GALEX NUV+FUV image showing the same eld. Bottom-left: CMD of the point sources within the aperture shown. The dashed lines indicates the 90% completeness limit and the dotted line the 50% limit. The errorbars indicate the typical uncertainties (from articial star tests) in the F814W magnitude and F606W-F814W color, as a function of F814W magnitude. Bottom-right: The CMD of a background region of the HST image away from bright sources. The aperture used was equal in area to the target aperture.

SECCO1 was one of the very unusual “blue blobs,” said Michael Jones, a postdoctoral fellow in the UArizona Steward Observatory and lead author of a study that describes the new stellar systems.

“It’s a lesson in the unexpected,” Jones said. “When you’re looking for things, you’re not necessarily going to find the thing you’re looking for, but you might find something else very interesting.”

The team obtained their observations from the Hubble Space Telescope, the Very Large Array telescope in New Mexico and the Very Large Telescope in Chile. Study co-author Michele Bellazzini, with the Istituto Nazionale di Astrofisica in Italy, led the analysis of the data from Very Large Telescope and has submitted a companion paper focusing on that data.

Together, the team learned that most of the stars in each system are very blue and very young and that they contain very little atomic hydrogen gas. This is significant because star formation begins with atomic hydrogen gas, which eventually evolves into dense clouds of molecular hydrogen gas before forming into stars.

“We observed that most of the systems lack atomic gas, but that doesn’t mean there isn’t molecular gas,” Jones said. “In fact, there must be some molecular gas because they are still forming stars. The existence of mostly young stars and little gas signals that these systems must have lost their gas recently.”

Top-left: False color HST F606W+F814W image of BC5. The dashed green ellipse and circle show the regions used to construct the CMD. The component BC5c was identied via H emission (Paper I) to be at the same velocity as the main body, but may only be a single cluster of stars. Top-right: GALEX NUV+FUV image showing the same eld. Bottom: CMD within the apertures shown (left) and a blank eld aperture (right).

The combination of blue stars and lack of gas was unexpected, as was a lack of older stars in the systems. Most galaxies have older stars, which astronomers refer to as being “red and dead.”

“Stars that are born red are lower mass and therefore live longer than blue stars, which burn fast and die young, so old red stars are usually the last ones left living,” Jones said. “And they’re dead because they don’t have any more gas with which to form new stars. These blue stars are like an oasis in the desert, basically.”

The fact that the new stellar systems are abundant in metals hints at how they might have formed.

“To astronomers, metals are any element heavier than helium,” Jones said. “This tells us that these stellar systems formed from gas that was stripped from a big galaxy, because how metals are built up is by many repeated episodes of star formation, and you only really get that in a big galaxy.”

There are two main ways gas can be stripped from a galaxy. The first is tidal stripping, which occurs when two big galaxies pass by each other and gravitationally tear away gas and stars. The other is what’s known as ram pressure stripping.

“This is like if you belly flop into a swimming pool,” Jones said. “When a galaxy belly flops into a cluster that is full of hot gas, then its gas gets forced out behind it. That’s the mechanism that we think we’re seeing here to create these objects.”

The team prefers the ram pressure stripping explanation because in order for the blue blobs to have become as isolated as they are, they must have been moving very quickly, and the speed of tidal stripping is low compared to ram pressure stripping. Astronomers expect that one day these systems will eventually split off into individual clusters of stars and spread out across the larger galaxy cluster.

What researchers have learned feeds into the larger “story of recycling of gas and stars in the universe,” Sand said. “We think that this belly flopping process changes a lot of spiral galaxies into elliptical galaxies on some level, so learning more about the general process teaches us more about galaxy formation.”

Krypton in the Chassigny meteorite shows Mars accreted chondritic volatiles before nebular gases

by Sandrine Péron, Sujoy Mukhopadhyay in Science

A new study of an old meteorite contradicts current thinking about how rocky planets like the Earth and Mars acquire volatile elements such as hydrogen, carbon, oxygen, nitrogen and noble gases as they form.

A basic assumption about planet formation is that planets first collect these volatiles from the nebula around a young star, said Sandrine Péron, a postdoctoral scholar working with Professor Sujoy Mukhopadhyay in the Department of Earth and Planetary Sciences, University of California, Davis. Because the planet is a ball of molten rock at this point, these elements initially dissolve into the magma ocean and then degass back into the atmosphere. Later on, chondritic meteorites crashing into the young planet deliver more volatile materials.

So scientists expect that the volatile elements in the interior of the planet should reflect the composition of the solar nebula, or a mixture of solar and meteoritic volatiles, while the volatiles in the atmosphere would come mostly from meteorites. These two sources — solar vs. chondritic — can be distinguished by the ratios of isotopes of noble gases, in particular krypton.

Mars is of special interest because it formed relatively quickly — solidifying in about 4 million years after the birth of the Solar System, while the Earth took 50 to 100 million years to form.

“We can reconstruct the history of volatile delivery in the first few million years of the Solar System,” Péron said.

Diagram illustrating a possible scenario for volatile delivery to Mars.

Some meteorites that fall to Earth come from Mars. Most come from surface rocks that have been exposed to Mars’ atmosphere. The Chassigny meteorite, which fell to Earth in north-eastern France in 1815, is rare and unusual because it is thought to represent the interior of the planet. By making extremely careful measurements of minute quantities of krypton isotopes in samples of the meteorite using a new method set up at the UC Davis Noble Gas Laboratory, the researchers could deduce the origin of elements in the rock.

“Because of their low abundance, krypton isotopes are challenging to measure,” Péron said.

Surprisingly, the krypton isotopes in the meteorite correspond to those from chondritic meteorites, not the solar nebula. That means that meteorites were delivering volatile elements to the forming planet much earlier than previously thought, and in the presence of the nebula, reversing conventional thinking.

“The Martian interior composition for krypton is nearly purely chondritic, but the atmosphere is solar,” Péron said. “It’s very distinct.”

The results show that Mars’ atmosphere cannot have formed purely by outgassing from the mantle, as that would have given it a chondritic composition. The planet must have acquired atmosphere from the solar nebula, after the magma ocean cooled, to prevent substantial mixing between interior chondritic gases and atmospheric solar gases.

The new results suggest that Mars’ growth was completed before the solar nebula was dissipated by radiation from the Sun. But the irradiation should also have blown off the nebular atmosphere on Mars, suggesting that atmospheric krypton must have somehow been preserved, possibly trapped underground or in polar ice caps.

“However, that would require Mars to have been cold in the immediate aftermath of its accretion,” Mukhopadhyay said. “While our study clearly points to the chondritic gases in the Martian interior, it also raises some interesting questions about the origin and composition of Mars’ early atmosphere.”

ALMA Images the Eccentric HD 53143 Debris Disk

by MacGregor et al. in The Astrophysical Journal Letters

Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have imaged the debris disk of the nearby star HD 53143 at millimeter wavelengths for the first time, and it looks nothing like they expected. Based on early coronagraphic data, scientists expected ALMA to confirm the debris disk as a face-on ring peppered with clumps of dust. Instead, the observations took a surprise turn, revealing the most complicated and eccentric debris disk observed to date.

HD 53143 — a roughly billion-year-old Sun-like star located 59.8 light-years from Earth in the Carina constellation — was first observed with the coronagraphic Advanced Camera for Surveys on the Hubble Space Telescope (HST) in 2006. It also is surrounded by a debris disk — a belt of comets orbiting a star that are constantly colliding and grinding down into smaller dust and debris — that scientists previously believed to be a face-on ring similar to the debris disk surrounding our Sun, more commonly known as the Kuiper Belt.

Artist’s impression of the billion-year-old Sun-like star, HD 53143, and its highly eccentric debris disk. The star and a second inner disk are shown near the southern foci of the elliptical debris disk. A planet, which scientists assume is shaping the disk through gravitational force, is shown to the north. Debris disks are the fossils of planetary formation and since we can’t directly study our own disk — also known as the Kuiper Belt — scientists glean information about the formation of our Solar System by studying those we can see from a distance. Credit: ALMA (ESO/NAOJ/NRAO); M. Weiss (NRAO/AUI/NSF)

The new observations were made of HD 53143 using the highly-sensitive Band 6 receivers on ALMA, an observatory co-operated by the U.S. National Science Foundation’s National Radio Astronomy Observatory (NRAO), and have revealed that the star system’s debris disk is actually highly eccentric. In ring-shaped debris disks, the star is typically located at or near the center of the disk. But in elliptically-shaped eccentric disks, the star resides at one focus of the ellipse, far away from the disk’s center. Such is the case with HD 53143, which wasn’t seen in previous coronagraphic studies because coronagraphs purposely block the light of a star in order to more clearly see nearby objects. The star system may also be harboring a second disk and at least one planet.

“Until now, scientists had never seen a debris disk with such a complicated structure. In addition to being an ellipse with a star at one focus, it also likely has a second inner disk that is misaligned or tilted relative to the outer disk,” said Meredith MacGregor, an assistant professor at the Center for Astrophysics and Space Astronomy (CASA) and Department of Astrophysical and Planetary Sciences (APS) at CU Boulder, and the lead author on the study. “In order to produce this structure, there must be a planet or planets in the system that are gravitationally perturbing the material in the disk.”

HST ACS coronagraphic data shows the region surrounding HD 53143. Because coronagraphic masks block out starlight to reveal features of the regions surrounding stars, the eccentric disk, and inner disk, of HD 53143 were originally “hidden” from scientists. Credit: ALMA(ESO/NAOJ/NRAO); NASA/ESA Hubble, P. Kalas (UC Berkeley); S. Dagnello (NRAO/AUI/NSF)

This level of eccentricity, MacGregor said, makes HD 53143 the most eccentric debris disk observed to date, being twice as eccentric as the Fomalhaut debris disk, which MacGregor fully imaged at millimeter wavelengths using ALMA in 2017. “So far, we have not found many disks with a significant eccentricity. In general, we don’t expect disks to be very eccentric unless something, like a planet, is sculpting them and forcing them to be eccentric. Without that force, orbits tend to circularize, like what we see in our own Solar System.”

Importantly, MacGregor notes that debris disks aren’t just collections of dust and rocks in space. They are a historical record of planetary formation and how planetary systems evolve over time. and provide a peek into their futures. “We can’t study the formation of Earth and the Solar System directly, but we can study other systems that appear similar to but younger than our own. It’s a bit like looking back in time,” she said. “Debris disks are the fossil record of planet formation, and this new result is confirmation that there is much more to be learned from these systems and that knowledge may provide a glimpse into the complicated dynamics of young star systems similar to our own Solar System.”

Dr. Joe Pesce, NSF program officer for ALMA, added, “We are finding planets everywhere we look, and these fabulous results by ALMA are showing us how planets form — both those around other stars and in our own Solar System. This research demonstrates how astronomy works and how progress is made, informing not only what we know about the field but also about ourselves.”

Gaia Data Release 3: Stellar multiplicity, a teaser for the hidden treasure

by Gaia Collaboration et al. in Astronomy & Astrophysics

Space scientists have recently announced the discovery of a ‘super Jupiter’ orbiting a white dwarf, the first detected using direct observations with the European Space Agency (ESA)’s Gaia mission.

The discovery forms part of a treasure trove of data made available in Gaia’s Data Release 3, which provides the most detailed survey of our galactic neighbourhood to date. Observations made by the Gaia observatory, which orbits a point in space about 1.5 million km from Earth, will allow astronomers to create the most accurate and complete multi-dimensional map of the Milky Way and better understand our place in the Universe.

Martin Barstow, Professor of Astrophysics and Space Science at the University of Leicester and Director of Strategic Partnerships for Space Park Leicester, is part of the Gaia collaboration to have co-authored multiple papers using the new data. Other highlights of Data Release 3 include description of ‘starquakes’, stellar DNA and a new binary star catalogue of more than 800,000 binary systems. Before Gaia launched in 2013, only around 30,000 binaries were known in our galaxy.

Professor Barstow said: “Gaia data has been moving through astronomy like a tidal wave. It’s the most productive observatory we have available to use right now, and it’s transforming both astronomy and our understanding of the Universe.
“This Data Release 3 is a complete step change. All the data we have catalogued using spectra — stellar distances, ages, composition, and more — adds an extra dimension to what we know about the stars in our galaxy, and represents a huge leap forward.”

Observations of exoplanets orbiting white dwarfs is notoriously difficult. White dwarfs are the core remnant of stars not massive enough to become a black hole or neutron star. However, by analysing the motion of the metal-rich white dwarf WD 0141–675 and noting a ‘wobble’ in its orbit, researchers inferred the existence of a companion object with a mass around nine times that of Jupiter. Too small to be a star, this must be an exoplanet. This ‘super Jupiter’ is only the third known exoplanet to orbit a white dwarf, and makes WD 0141–675 the closest white dwarf to Earth to host a planet.

Gaia’s Data Release 3 also expands astronomers’ understanding of binary systems, where two stars are gravitationally bound to one another. Sirius, the brightest star visible from Earth (after our Sun), is a binary system comprising a main sequence star, Sirius A, and a faint white dwarf companion, Sirius B.

These new datasets both refine the stellar catalogue of known binaries and add many more new such systems, bringing the total of known binary systems from around 300,000 before Data Release 3 to more than 800,000. Researchers detect binaries using Gaia’s radial velocity spectrometer and a variety of techniques; astrometry: by detecting the motion of source objects which are not uniform and are observed to ‘wobble’ or otherwise change direction from what would otherwise be expected; photometry: when aligned with Gaia’s line of sight, where one star is observed to pass in front of another and periodically ‘eclipse’ its companion; and spectroscopy: these binaries have a radial velocity that varies periodically, depending on whether a star approaches or recedes from our viewpoint at Earth.

Professor Barstow continued: “We have so much more data on binaries with this release and, crucially, that data is so much more precise than what has gone before. “Once you have more precise data about a binary system you can work out all sorts of things such as ages and composition: all aspects we haven’t had information on before.
“And by answering those questions, we can start to understand more of the fundamentals about how our Universe works, including how stars live and die.”

ALMA reveals extended cool gas and hot ionized out in a typical star-forming galaxy at z = 7.13

by Hollis Akins, Seiji Fujimoto, Kristian Finlator, Darach Watson, et al in The Astrophysical Journal

Scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) — an international observatory co-operated by the US National Science Foundation’s National Radio Astronomy Observatory (NRAO) — have observed a significant amount of cold, neutral gas in the outer regions of the young galaxy A1689-zD1, as well as outflows of hot gas coming from the galaxy’s center. These results may shed light on a critical stage of galactic evolution for early galaxies, where young galaxies begin the transformation to be increasingly like their later, more structured cousins.

A1689-zD1 — a young, active, star-forming galaxy that is slightly less luminous and less massive than the Milky Way — is located roughly 13 billion light-years away from Earth in the Virgo constellation cluster. It was discovered hiding out behind the Abell 1689 galaxy cluster in 2007 and confirmed in 2015 thanks to gravitational lensing, which amplified the brightness of the young galaxy by more than 9x. Since then, scientists have continued to study the galaxy as a possible analog for the evolution of other “normal” galaxies. That label — normal — is an important distinction that has helped researchers divide A1689-zD1’s behaviors and characteristics into two buckets: typical and uncommon, with the uncommon characteristics mimicking those of later and more massive galaxies.

This artist’s conception illustrates the previously unknown complexity of the young galaxy, A1689-zD1. Reaching far beyond the center of the galaxy, shown here in pink, is an abundant halo of cold carbon gas. For scientists, this uncommon feature indicates that the galaxy may be much larger than previously believed and that early stages of normal galaxy formation may have been more active and dynamic than theorized. To the upper left and lower right are outflows of hot, ionized gas pushing outward from the center of the galaxy, shown here in red. Scientists believe it is possible that these outflows have something, though they don’t yet know what, to do with the presence of cold carbon gas in the outer reaches of the galaxy. Credit: ALMA (ESO/NAOJ/NRAO), B. Saxton (NRAO/AUI/NSF)

“A1689-zD1 is located in the very early Universe — only 700 million years after the Big Bang. This is the era where galaxies were just beginning to form,” said Hollis Akins, an undergraduate student in astronomy at Grinnell College and the lead author of the research. “What we’re seeing in these new observations is evidence of processes that may contribute to the evolution of what we call normal galaxies as opposed to massive galaxies. More importantly, these processes are ones we did not previously believe applied to these normal galaxies.”

One of these uncommon processes is the galaxy’s production and distribution of star-forming fuel, and potentially a lot of it. The team used ALMA’s highly-sensitive Band 6 receiver to home in on a halo of carbon gas that extends far beyond the center of the young galaxy. This could be evidence of ongoing star formation in the same region or the result of structural disruptions, such as mergers or outflows, in the earliest stages of the galaxy’s formation.

According to Akins, this is unusual for early galaxies. “The carbon gas we observed in this galaxy is typically found in the same regions as neutral hydrogen gas, which is also where new stars tend to form. If that is the case with A1689-zD1, the galaxy is likely much larger than previously thought. It’s also possible that this halo is a remnant of previous galactic activity, like mergers that exerted complex gravitational forces on the galaxy leading to the ejection of a lot of neutral gas out to these large distances. In either case, the early evolution of this galaxy was likely active and dynamic, and we’re learning that this may be a common, although previously unobserved, theme in early galaxy formation.”

More than just uncommon, the discovery could have significant implications for the study of galactic evolution, particularly as radio observations uncover details unseen at optical wavelengths. Seiji Fujimoto, a postdoctoral researcher at the Niels Bohr Institute’s Cosmic Dawn Center, and a co-author of the research said, “The emission from the carbon gas in A1689-zD1 is much more extended than what was observed with Hubble Space Telescope, and this could mean that early galaxies are not as small as they appear. If, in fact, early galaxies are larger than we previously believed this would have a major impact on the theory of galaxy formation and evolution in the early Universe.”

A1689-zD1 is a young, star-forming galaxy located in the Virgo constellation cluster, roughly 13 billion light-years away from Earth. Credit: IAU/Sky & Telescope

Led by Akins, the team also observed outflows of hot, ionized gas — commonly caused by violent galactic activity like supernovae — pushing outward from the center of the galaxy. It’s possible, given their potentially explosive nature, that the outflows have something to do with the carbon halo.

“Outflows occur as a result of violent activity, such as the explosion of supernovae — which blast nearby gaseous material out of the galaxy — or black holes in the centers of galaxies — which have strong magnetic effects that can eject material in powerful jets. Because of this, there’s a strong possibility that the hot outflows have something to do with the presence of the cold carbon halo,” said Akins. “And that further highlights the importance of the multiphase, or hot to cold, nature of the outflowing gas.”

Darach Watson, an associate professor at the Niels Bohr Institute’s Cosmic Dawn Center, and co-author of the new research confirmed A1689-zD1 as a high-redshift galaxy in 2015, making it the most distant dusty galaxy known. “We have seen this type of extended gas halo emission from galaxies that formed later in the Universe, but seeing it in such an early galaxy means that this type of behavior is universal even in the more modest galaxies that formed most of the stars in the early Universe. Understanding how these processes occurred in such a young galaxy is critical to understanding how star-formation happens in the early Universe.”

Kirsten Knudsen, a professor of astrophysics in the Department of Space, Earth, and Environment at Chalmers University of Technology, and co-author of the research found evidence of A1689-zD1’s dust continuum in 2017. Knudsen pointed out the serendipitous role of extreme gravitational lensing in making each new discovery in the research possible. “Because A1689-zD1 is magnified more than nine times, we can see critical details that are otherwise difficult to observe in ordinary observations of such distant galaxies. Ultimately, what we’re seeing here is that early Universe galaxies are very complex, and this galaxy will continue to present new research challenges and results for some time.”

V1674 Hercules: It is Blowing out a Wind

by C. E. Woodward, R. Mark Wagner, Sumner Starrfield in Research Notes of the AAS

Astronomers are buzzing after observing the fastest nova ever recorded. The unusual event drew scientists’ attention to an even more unusual star. As they study it, they may find answers to not only the nova’s many baffling traits, but to larger questions about the chemistry of our solar system, the death of stars and the evolution of the universe.

The research team, led by Arizona State University Regents Professor Sumner Starrfield, Professor Charles Woodward from University of Minnesota and Research Scientist Mark Wagner from The Ohio State University, co-authored a report.

A nova is a sudden explosion of bright light from a two-star system. Every nova is created by a white dwarf — the very dense leftover core of a star — and a nearby companion star. Over time, the white dwarf draws matter from its companion, which falls onto the white dwarf. The white dwarf heats this material, causing an uncontrolled reaction that releases a burst of energy. The explosion shoots the matter away at high speeds, which we observe as visible light. The bright nova usually fades over a couple of weeks or longer. On June 12, 2021, the nova V1674 Hercules burst so bright that it was visible to the naked eye — but in just over one day, it was faint once more. It was like someone flicked a flashlight on and off. Nova events at this level of speed are rare, making this nova a precious study subject.

“It was only about one day, and the previous fastest nova was one we studied back in 1991, V838 Herculis, which declined in about two or three days,” says Starrfield, an astrophysicist in ASU’s School of Earth and Space Exploration.

V1674 Her spectra (dereddened, see Section 2). (top) Day 98.27 (blue) vs. day 312.78 (red, composite sum of 26 120 s exposures) illustrating the spectral evolution (offset = +16.0). (bottom) Day 312.78 time series spectra centered near Hα, highlighting changes in the emission line profile (spectra continuum normalized and smoothed with a 7th order Savitsky-Golay filter, with offsets for clarity). The P Cygni-like absorption component is indicated by the dotted red vertical line. Time increasing upwards (green arrow).

As the astronomy world watched V1674 Hercules, other researchers found that its speed wasn’t its only unusual trait. The light and energy it sends out is also pulsing like the sound of a reverberating bell. Every 501 seconds, there’s a wobble that observers can see in both visible light waves and X-rays. A year after its explosion, the nova is still showing this wobble, and it seems it’s been going on for even longer. Starrfield and his colleagues have continued to study this quirk.

“The most unusual thing is that this oscillation was seen before the outburst, but it was also evident when the nova was some 10 magnitudes brighter,” says Wagner, who is also the head of science at the Large Binocular Telescope Observatory being used to observe the nova. “A mystery that people are trying to wrestle with is what’s driving this periodicity that you would see it over that range of brightness in the system.”

The team also noticed something strange as they monitored the matter ejected by the nova explosion — some kind of wind, which may be dependent on the positions of the white dwarf and its companion star, is shaping the flow of material into space surrounding the system. Though the fastest nova is (literally) flashy, the reason it’s worth further study is that novae can tell us important information about our solar system and even the universe as a whole.

A white dwarf collects and alters matter, then seasons the surrounding space with new material during a nova explosion. It’s an important part of the cycle of matter in space. The materials ejected by novae will eventually form new stellar systems. Such events helped form our solar system as well, ensuring that Earth is more than a lump of carbon.

“We’re always trying to figure out how the solar system formed, where the chemical elements in the solar system came from,” Starrfield says. “One of the things that we’re going to learn from this nova is, for example, how much lithium was produced by this explosion. We’re fairly sure now that a significant fraction of the lithium that we have on the Earth was produced by these kinds of explosions.”

Sometimes a white dwarf star doesn’t lose all of its collected matter during a nova explosion, so with each cycle, it gains mass. This would eventually make it unstable, and the white dwarf could generate a type 1a supernova, which is one of the brightest events in the universe. Each type 1a supernova reaches the same level of brightness, so they are known as standard candles.

“Standard candles are so bright that we can see them at great distances across the universe. By looking at how the brightness of light changes, we can ask questions about how the universe is accelerating or about the overall three-dimensional structure of the universe,” Woodward says. “This is one of the interesting reasons that we study some of these systems.”

Additionally, novae can tell us more about how stars in binary systems evolve to their death, a process that is not well understood. They also act as living laboratories where scientists can see nuclear physics in action and test theoretical concepts.

The nova took the astronomy world by surprise. It wasn’t on scientists’ radar until an amateur astronomer from Japan, Seidji Ueda, discovered and reported it. Citizen scientists play an increasingly important role in the field of astronomy, as does modern technology. Even though it is now too faint for other types of telescopes to see, the team is still able to monitor the nova thanks to the Large Binocular Telescope’s wide aperture and its observatory’s other equipment, including its pair of multi-object double spectrographs and exceptional PEPSI high resolution spectrograph. They plan to investigate the cause of the outburst and the processes that led to it, the reason for its record-breaking decline, the forces behind the observed wind, and the cause of its pulsing brightness.

The Heterogeneous Surface of Asteroid (16) Psyche

by Saverio Cambioni, Katherine de Kleer, Michael Shepard in Journal of Geophysical Research: Planets

Later this year, NASA is set to launch a probe the size of a tennis court to the asteroid belt, a region between the orbits of Mars and Jupiter where remnants of the early solar system circle the sun. Once inside the asteroid belt, the spacecraft will zero in on Psyche, a large, metal-rich asteroid that is thought to be the ancient core of an early planet. The probe, named after its asteroid target, will then spend close to two years orbiting and analyzing Psyche’s surface for clues to how early planetary bodies evolved.

Ahead of the mission, which is led by principal investigator Lindy Elkins-Tanton ’87, SM ’87, PhD ’02, planetary scientists at MIT and elsewhere have now provided a sneak peek of what the Psyche spacecraft might see when it reaches its destination.

In a paper, the team presents the most detailed maps of the asteroid’s surface properties to date, based on observations taken by a large array of ground telescopes in northern Chile. The maps reveal vast metal-rich regions sweeping across the asteroid’s surface, along with a large depression that appears to have a different surface texture between the interior and its rim; this difference could reflect a crater filled with finer sand and rimmed with rockier materials. Overall, Psyche’s surface was found to be surprisingly varied in its properties.

The new maps hint at the asteroid’s history. Its rocky regions could be vestiges of an ancient mantle — similar in composition to the rocky outermost layer of Earth, Mars, and the asteroid Vesta — or the imprint of past impacts by space rocks. Finally, craters that contain metallic material support the idea proposed by previous studies that the asteroid may have experienced early eruptions of metallic lava as its ancient core cooled.

“Psyche’s surface is very heterogeneous,” says lead author Saverio Cambioni, the Crosby Distinguished Postdoctoral Fellow in MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS). “It’s an evolved surface, and these maps confirm that metal-rich asteroids are interesting, enigmatic worlds. It’s another reason to look forward to the Psyche mission going to the asteroid.”

Cambioni’s co-authors are Katherine de Kleer, assistant professor of planetary science and astronomy at Caltech, and Michael Shepard, professor of environmental, geographical, and geological sciences at Bloomsburg University.

As the asteroid rotates during the observation epochs, the same facet of longitude α and latitude β is seen at different right ascensions R.A. and declinations decl. in the Atacama Large Millimeter Array (ALMA) images. We use the knowledge of the (R.A., decl.) of the projected facets and the (R.A., decl.) of the ALMA pixels to associate a thermal-emission curve to each facet. We then fit modeled thermal emission curves corresponding to different values of thermal inertia and dielectric constant to the observed thermal emission curves.

The surface of Psyche has been a focus of numerous previous mapping efforts. Researchers have observed the asteroid using various telescopes to measure light emitted from the asteroid at infrared wavelengths, which carry information about Psyche’s surface composition. However, these studies could not spatially resolve variations in composition over the surface.

Cambioni and his colleagues instead were able to see Psyche in finer detail, at a resolution of about 20 miles per pixel, using the combined power of the 66 radio antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile. Each antenna of ALMA measures light emitted from an object at millimeter wavelengths, within a range that is sensitive to temperature and certain electrical properties of surface materials.

“The signals of the ALMA antennas can be combined into a synthetic signal that’s equivalent to a telescope with a diameter of 16 kilometers (10 miles),” de Kleer says. “The larger the telescope, the higher the resolution.”

On June 19, 2019, ALMA focused its entire array on Psyche as it orbited and rotated within the asteroid belt. De Kleer collected data during this period and converted it into a map of thermal emissions across the asteroid’s surface, which the team reported in a 2021 study. Those same data were used by Shepard to produce the most recent high-resolution 3D shape model of Psyche, also published in 2021.

Atacama Large Millimeter Array (ALMA) data (top panel), global solution (left panels) and local solution (right panels) of the thermal emission of Psyche.

In the new study, Cambioni ran simulations of Psyche to see which surface properties might best match and explain the measured thermal emissions. In each of hundreds of simulated scenarios, he set the asteroid’s surface with different combinations of materials, such as areas of different metal abundances. He modeled the asteroid’s rotation and measured how simulated materials on the asteroid would give off thermal emissions. Cambioni then looked for the simulated emissions that best matched the actual emissions measured by ALMA. That scenario, he reasoned, would reveal the likeliest map of the asteroid’s surface materials.

“We ran these simulations area by area so we could catch differences in surface properties,” Cambioni says.

The study produced detailed maps of Psyche’s surface properties, showing that the asteroid’s façade is likely covered in a large diversity of materials. The researchers confirmed that, overall, Psyche’s surface is rich in metals, but the abundance of metals and silicates varies across its surface. This may be a further hint that, early in its formation, the asteroid may have had a silicate-rich mantle that has since disappeared.

They also found that, as the asteroid rotates, the material at the bottom of a large depression — likely a crater — changes temperature much faster than material along the rim. This suggests that the crater bottom is covered in “ponds” of fine-grained material, like sand on Earth, which heats up quickly, whereas the crater rims are composed of rockier, slower-to-warm materials.

“Ponds of fine-grained materials have been seen on small asteroids, whose gravity is low enough for impacts to shake the surface and cause finer materials to pool,” Cambioni says. “But Psyche is a large body, so if fine-grained materials accumulated on the bottom of the depression, this is interesting and somewhat mysterious.”
“These data show that Psyche’s surface is heterogeneous, with possible remarkable variations in composition,” says Simone Marchi, staff scientist at the Southwest Research Institute and a co-investigator on NASA’s Psyche mission, who was not involved in the current study. “One of the primary goals of the Psyche mission is to study the composition of the asteroid surface using its gamma rays and neutron spectrometer and a color imager. So, the possible presence of compositional heterogeneties is something that the Psyche Science Team is eager to study more.”

The 30 Doradus Molecular Cloud at 0.4 pc Resolution with the Atacama Large Millimeter/submillimeter Array: Physical Properties and the Boundedness of CO-emitting Structures

by Tony Wong, Luuk Oudshoorn, Eliyahu Sofovich, Alex Green, et al in The Astrophysical Journal

Astronomers have unveiled intricate details of the star-forming region 30 Doradus, also known as the Tarantula Nebula, using new observations from the Atacama Large Millimeter/submillimeter Array (ALMA). Now we can see the nebula in a new light, with wispy gas clouds that provide insight into how massive stars shape this region.

“These fragments may be the remains of once-larger clouds that have been shredded by the enormous energy being released by young and massive stars, a process dubbed feedback,” says Tony Wong, who led the research on 30 Doradus presented today at the American Astronomical Society (AAS) meeting. Astronomers originally thought the gas in these areas would be too sparse and too overwhelmed by this turbulent feedback for gravity to pull it together to form new stars. But the new data also reveal much denser filaments where gravity’s role is still significant. “Our results imply that even in the presence of very strong feedback, gravity can exert a strong influence and lead to a continuation of star formation,” adds Wong, who is a professor at the University of Illinois at Urbana-Champaign, USA.

This composite image shows the star-forming region 30 Doradus, also known as the Tarantula Nebula. The background image, taken in the infrared, is itself a composite: it was captured by the HAWK-I instrument on ESO’s Very Large Telescope (VLT) and the Visible and Infrared Survey Telescope for Astronomy (VISTA), shows bright stars and light, pinkish clouds of hot gas. The bright red-yellow streaks that have been superimposed on the image come from radio observations taken by the Atacama Large Millimeter/submillimeter Array (ALMA), revealing regions of cold, dense gas which have the potential to collapse and form stars. The unique web-like structure of the gas clouds led astronomers to the nebula’s spidery nickname. **Credit:** ESO, ALMA (ESO/NAOJ/NRAO)/Wong et al., ESO/M.-R. Cioni/VISTA Magellanic Cloud survey. Acknowledgment: Cambridge Astronomical Survey Unit

Located in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way, the Tarantula Nebula is one of the brightest and most active star-forming regions in our galactic neighbourhood, lying about 170,000 light-years away from Earth. At its heart are some of the most massive stars known, a few with more than 150 times the mass of our Sun, making the region perfect for studying how gas clouds collapse under gravity to form new stars.

“What makes 30 Doradus unique is that it is close enough for us to study in detail how stars are forming, and yet its properties are similar to those found in very distant galaxies, when the Universe was young,” said Guido De Marchi, a scientist at the European Space Agency (ESA) and a co-author of the paper presenting the new research. “Thanks to 30 Doradus, we can study how stars used to form 10 billion years ago when most stars were born.”

While most of the previous studies of the Tarantula Nebula have focused on its centre, astronomers have long known that massive star formation is happening elsewhere too. To better understand this process, the team conducted high-resolution observations covering a large region of the nebula. Using ALMA, they measured the emission of light from carbon monoxide gas. This allowed them to map the large, cold gas clouds in the nebula that collapse to give birth to new stars — and how they change as huge amounts of energy are released by those young stars.

“We were expecting to find that parts of the cloud closest to the young massive stars would show the clearest signs of gravity being overwhelmed by feedback,” says Wong. “We found instead that gravity is still important in these feedback-exposed regions — at least for parts of the cloud that are sufficiently dense.”

Zero moment (integrated intensity in K kms−1, middle) and first moment (intensity-weighted mean velocity in kms−1, right) images for the CO cube, after applying the dilated mask. The outline of the ALMA footprint is indicated by a dotted contour. In the left panel, the zero moment contours are overlaid on a Hubble Space Telescope RGB image from the HTTP survey (Sabbi et al. 2013) with 1.6 μm in red, 775 nm in green, and 555 nm in blue.

In the image released, we see the new ALMA data overlaid on a previous infrared image of the same region that shows bright stars and light pinkish clouds of hot gas, taken with ESO’s Very Large Telescope (VLT) and ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA). The composition shows the distinct, web-like shape of the Tarantula Nebula’s gas clouds that gave rise to its spidery name. The new ALMA data comprise the bright red-yellow streaks in the image: very cold and dense gas that could one day collapse and form stars.

The new research contains detailed clues about how gravity behaves in the Tarantula Nebula’s star-forming regions, but the work is far from finished. “There is still much more to do with this fantastic data set, and we are releasing it publicly to encourage other researchers to conduct new investigations,” Wong concludes.

Gemini-LIGHTS: Herbig Ae/Be and massive T-Tauri protoplanetary disks imaged with Gemini Planet Imager

by Evan A. Rich, John D. Monnier, Alicia Aarnio, Anna S. E. Laws, Bet al in The Astronomical Journal

Finding forming planets is a tough but important job for astronomers: Only three planets have ever been discovered caught in the process of forming, and the most recent of these was found just weeks ago.

Evan Rich, a postdoctoral researcher at the University of Michigan, suggests that instead of looking for individual planets forming, astronomers might have better luck looking for the likely environments in which they form. In doing just that, Rich and a team of astronomers have found that systems with stars less than three solar masses are more likely to have large rings composed of tiny dust grains, about a micron in size — potential indications of planet formation — than larger stars and may have discovered a new planet around a very young star. Rich will present his findings, collected in the first summary paper produced from a survey called Gemini-Large Imaging with GPI Herbig/T-tauri Survey, or Gemini-LIGHTS, at the American Astronomical Society’s annual meeting this month.

A team imaged 44 targets in a survey called Gemini-Large Imaging with GPI Herbig/T-tauri Survey, or Gemini-LIGHTS. The astronomers detected some form of dust around 80% of the 44 targets. Credit: Evan Rich, University of Michigan

“It turns out that finding these planets in particular is very, very difficult,” Rich said. “So we’re taking the strategy of actually looking at the material itself rather than for the planet.
“What is the environment of planet formation? What are the dynamics? How do these differentiate between a very low mass star compared to a very high mass star? Does the temperature of the star have an effect on the disk? One of the ultimate goals is to question how all these parameters affect planet formation.”

Rich and his research team used the Gemini South Telescope in Chile to look at stars more massive than the sun to to study how planet formation here might be different. Specifically, the team used the Gemini Planet Imager to view the objects in infrared light, or light slightly redder than our eyes can see. The astronomers also looked at these stars in polarized light in order to look for dim material such as dust next to the stars themselves.

“The material we’re looking at is sometimes a million times dimmer than the star itself, and using these processes allows us to see that dim material around very bright stars,” Rich said. “What’s happening is the light from the star is scattering off the dust, like when light from the sun reflects off the surface of a pond.”

What you see reflected off the surface of a pond is unpolarized light, which means its lightwaves are vibrating in all directions. Polarizing the light aligns its vibrations into a single plane. Similarly, when light from stars scatters off dust grains orbiting the stars, the astronomers can distinguish between the unpolarized light of the star and the unpolarized light from the dust, and can allow them to observe the dust grains in this protoplanetary disk.

“In some ways, this is like using polarized sunglasses but instead of using the glasses to suppress the scattered light, we use it to enhance it,” said co-author John Monnier, U-M professor of astronomy.

The astronomers imaged 44 targets and detected some form of dust around 80% of them. The team released a gallery showing a range of different morphologies that tell the researchers about the dynamics happening within the disk itself.

“It’s truly incredible that we’re at a point right now in astronomy where not only are we able to get images of planet-forming disks around young stars, but we can populate entire galleries to sort and study, reconstructing planetary origin stories,” said Alicia Aarnio, assistant professor of physics and astronomy at the University of North Carolina-Greensboro, who led the target selection.
“The theory is that when planets form, they make almost perfect tree rings going out from the sun,” Rich said. “We think that if you see rings and gaps in the dust disk, there could be planets.”

The team has found so far that only systems with stars less than three solar masses have these rings. Stars above solar masses don’t seem to have the same rings, and since these rings are a potential signature of planet formation, this could be a good indicator of where and how planets are forming. The researchers also saw a pattern in the stars without dust.

“It was surprising to see that the presence of even a small companion to a host star, like a brown dwarf, dramatically reduced signs of ongoing planet formation,” Monnier.

This finding reinforces the idea that close binary stars seem to make planets less often than single stars, a result first proposed to explain data from the Kepler Space Telescope. The team found a host of objects orbiting the stars, including three brown dwarfs and one planetary-mass companion candidate just outside a planet-forming disk system, called V1295 Aql. This object appears to be about 13 times the mass of Jupiter, which puts it right on the edge between what’s considered a planet or what’s considered a brown dwarf star. If future observations confirm its orbit, it would be one of only a few known exoplanets around massive stars.

“The dust rings, gaps and spiral arms seen by Gemini are telling us how and when planets form in real-time. With more accurate simulations and new telescopes like the James Webb Space Telescope and the Extremely Large Telescope, we are zeroing in on the key ingredients to understand how our solar system came to be,” said Jaehan Bae, a planet formation theorist and former postdoctoral fellow and Ph.D. student at U-M, who is now an assistant professor of astronomy at the University of Florida.

The Lingering Death of Periodic Near-Sun Comet 323P/SOHO

by Man-To Hui, David J. Tholen, Rainer Kracht, Chan-Kao Chang, Paul A. Wiegert, Quan-Zhi Ye, Max Mutchler in The Astronomical Journal

Astronomers using a fleet of world leading telescopes on the ground and in space have captured images of a periodic rocky near-Sun comet breaking apart. This is the first time such a comet has been caught in the act of disintegrating and could help explain the scarcity of such periodic near-Sun comets.

The Solar System is a dangerous place. In textbooks we see figures of celestial bodies orbiting around the Sun in orderly orbits. But that’s because if an object’s orbit doesn’t fit this pattern, gravitational effects from other objects destabilize the orbit. One common fate for such ejected bodies is to become comets in near-Sun orbits where they will eventually plunge into the Sun. Because these comets pass so close to the Sun, they are difficult to spot and study. Most have been discovered by accident in solar telescope observations. But even taking this difficulty into account, there are far fewer near-Sun comets than expected, indicating that something is destroying them before they get a chance to make their fatal final dive into the Sun.

The appearance of 323P in our Subaru (2020 December 21, r-band), CFHT (2021 February 6, 8, and 11, *gri* filter), LDT (2021 February 16, r and VR filters), and GN (2021 February 13 and March 3, r-band) images from late 2020 December to early 2021 March. Each panel is median combined from individual exposures in the aforementioned corresponding filters from the same observing night, with registration on the comet and background sources masked out, except for the Subaru panel, which is an average from the background-offset image sequence and then convolved with a Gaussian of two pixels in FWHM so as to cosmetically suppress background noise. The antisolar direction ( −⊙ ) and the negative heliocentric velocity of the comet projected onto the sky plane (− V ) are shown as the arrows. Corresponding scale bars are given in each panel. Equatorial J2000 north is up and east is left.

To better understand these comets, a group of astronomers from Macau, the US, Germany, Taiwan, and Canada observed an elusive near-Sun comet called 323P/SOHO with multiple telescopes including the Subaru Telescope, the Canada France Hawaii Telescope (CFHT), the Gemini North telescope, Lowell’s Discovery Telescope, and the Hubble Space Telescope. The orbit of 323P/SOHO was poorly constrained, so the group didn’t know exactly where to look for it, but the wide field of view of the Subaru Telescope allowed them to “cast a wide net” and find the comet as it approached the Sun. This was the first time 323P/SOHO was captured by a ground-based telescope. With this data, the researchers were able to better constrain the orbit, they knew where to point the other telescopes and were waiting when 323P/SOHO started to move away from the Sun again.

To their surprise the researchers found that 323P/SOHO had changed remarkably during its close passage by the Sun. In the Subaru Telescope data, 323P/SOHO was just a dot, but in follow-up data it had a long comet tail of ejected dust. The researchers believe that the intense radiation from the Sun caused parts of the comet to break off due to thermal fracturing, similar to how ice cubes crack when you pour a hot drink over them. This mass loss mechanism could help explain what happens to near-Sun comets and why there are so few of them left.

But the team’s results raised more questions than they answered. They found that 323P/SOHO rotates rapidly, taking just more than half an hour per revolution, and that its color is unlike anything else in the Solar System. Observations of other near-Sun comets are needed to see if they also share these traits.

“We couldn’t have made this discovery without observations from the telescopes on Maunakea, made possible by the University of Hawaii.” says Man-To Hui, who was a University of Hawaii researcher at the time of the observations, and now an assistant professor from Macau University of Science and Technology, “The observations from the Subaru Telescope were the initiator, shrinking orbit uncertainties and making follow-up observations possible. CFHT provided the best coverage data and Gemini provided the densest data points.”