astronomy

seismic-data-shows-mars-is-often-pummeled-by-planet-shaking-meteorites

Seismic data shows Mars is often pummeled by planet-shaking meteorites

astronomy, Impacts, Mars, meteorites, planetary science, Science, seismology / /

Brace for impact —

Seismic information now allows us to make a planet-wide estimate of impact rates.

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One of the craters identified seismically, then confirmed through orbital images.

Enlarge / One of the craters identified seismically, then confirmed through orbital images.

Mars trembles with marsquakes, but not all of them are driven by phenomena that occur beneath the surface—many are the aftermath of meteorite strikes.

Meteorites crash down to Mars every day. After analyzing data from NASA’s InSight lander, an international team of researchers noticed that its seismometer, SEIS, detected six nearby seismic events. These were linked to the same acoustic atmospheric signal that meteorites generate when whizzing through the atmosphere of Mars. Further investigation identified all six as part of an entirely new class of quakes known as VF (very high frequency) events.

The collisions that generate VF marsquakes occur in fractions of a second, much less time than the few seconds it takes tectonic processes to cause quakes similar in size. This is some of the key seismological data that has helped us understand the occurrence of earthquakes caused by meteoric impacts on Mars. This is also the first time seismic data was used to determine how frequently impact craters are formed.

“Although a non-impact origin cannot be definitively excluded for each VF event, we show that the VF class as a whole is plausibly caused by meteorite impacts,” the researchers said in a study recently published in Nature.

Seismic shift

Scientists had typically determined the approximate meteorite impact rate on Mars by comparing the frequency of craters on its surface to the expected rate of impacts calculated using counts of lunar craters that were left behind by meteorites. Models of the lunar cratering rate were then adjusted to fit Martian conditions.

Looking to the Moon as a basis for comparison was not ideal, as Mars is especially prone to being hit by meteorites. The red planet is not only a more massive body that has greater gravitational pull, but it is located near the asteroid belt.

Another issue is that lunar craters are often better preserved than Martian craters because there is no place in the Solar System dustier than Mars. Craters in orbital images are often partly obscured by dust, which makes them difficult to identify. Sandstorms can complicate matters by covering craters in more dust and debris (something that cannot occur on the Moon due to the absence of wind).

InSight deployed its SEIS instrument after it landed in the Elysium Planitia region of Mars. In addition to detecting tectonic activity, the seismometer can potentially determine the impact rate through seismic data. When meteorites strike Mars, they produce seismic waves just like tectonic marsquakes do, and the waves can be detected by seismometers when they travel through the mantle and crust. An immense quake picked up by SEIS was linked to a crater 150 meters (492 feet) wide. SEIS would later detect five more marsquakes that were all associated with an acoustic signal (detected by a different sensor on InSight) that is a telltale sign of a falling meteorite.

A huge impact

Something else stood out about the six impact-driven marsquakes detected with seismic data. Because of the velocity of meteorites (over 3,000 meters or 9,842 feet per second), these events happened faster than any other type of marsquake, even faster than quakes in the high frequency (HF) class. That’s how they earned their own classification: very high frequency, or VF, quakes. When the InSight team used the Mars Reconnaissance Orbiter’s (MRO) Context Camera (CTX) to image the locations of the events picked up by SEIS, there were new craters present in the images.

There are additional seismic events that haven’t been assigned to craters yet. They are thought to be small craters formed by meteorites about the size of basketballs, which are extremely difficult to see in orbital images from MRO.

The researchers were able to use SEIS data to estimate the diameters of craters based on distance from InSight (according to how long it took seismic waves to reach the spacecraft) and the magnitude of the VF marsquakes associated with them. They were also able to derive the frequency of quakes picked up by SEIS. Once a frequency estimate based on the data was applied to the entire surface area of Mars, they estimated that around 280 to 360 VF quakes occur each year.

“The case is strong that the unique VF marsquake class is consistent with impacts,” they said in the same study. “It is, therefore, worthwhile considering the implications of attributing all VF events to meteoroid impacts.”

Their detection has added to the estimated number of impact craters on Mars since many could not be seen from space before. What can VF impacts tell us? The impact rate on a planet or moon is important for determining the age of that object’s surface. Using impacts has helped us determine that the surface of Venus is constantly being renewed by volcanic activity, while most of the surface of Mars has not been covered in lava for billions of years.

Figuring out the rate of meteorite impacts can also help protect spacecraft and, someday, maybe Martian astronauts, from potential hazards. The study suggests that there are periods where impacts are more or less frequent, so it might be possible to predict when the sky is a bit more likely to be clear of falling space rocks—and when it isn’t. Meteorites are not much of a danger to Earth since most of them burn up in the atmosphere. Mars has a much thinner atmosphere that more can make it through, and there is no umbrella for a meteor shower.

Nature Astronomy, 2024. DOI: 10.1038/s41550-024-02301-z

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Nearby star cluster houses unusually large black hole

astronomy, astrophysics, black hole, globular cluster, Science / /

Big, but not that big —

Fast-moving stars imply that there’s an intermediate-mass black hole there.

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Three panel image, with zoom increasing from left to right. Left most panel is a wide view of the globular cluster; right is a zoom in to the area where its central black hole must reside.

Enlarge / From left to right, zooming in from the globular cluster to the site of its black hole.

ESA/Hubble & NASA, M. Häberle

Supermassive black holes appear to reside at the center of every galaxy and to have done so since galaxies formed early in the history of the Universe. Currently, however, we can’t entirely explain their existence, since it’s difficult to understand how they could grow quickly enough to reach the cutoff for supermassive as quickly as they did.

A possible bit of evidence was recently found by using about 20 years of data from the Hubble Space Telescope. The data comes from a globular cluster of stars that’s thought to be the remains of a dwarf galaxy and shows that a group of stars near the cluster’s core are moving so fast that they should have been ejected from it entirely. That implies that something massive is keeping them there, which the researchers argue is a rare intermediate-mass black hole, weighing in at over 8,000 times the mass of the Sun.

Moving fast

The fast-moving stars reside in Omega Centauri, the largest globular cluster in the Milky Way. With an estimated 10 million stars, it’s a crowded environment, but observations are aided by its relative proximity, at “only” 17,000 light-years away. Those observations have been hinting that there might be a central black hole within the globular cluster, but the evidence has not been decisive.

The new work, done by a large international team, used over 500 images of Omega Centauri, taken by the Hubble Space Telescope over the course of 20 years. This allowed them to track the motion of stars within the cluster, allowing an estimate of their speed relative to the cluster’s center of mass. While this has been done previously, the most recent data allowed an update that reduced the uncertainty in the stars’ velocity.

Within the update data, a number of stars near the cluster’s center stood out for their extreme velocities: seven of them were moving fast enough that the gravitational pull of the cluster isn’t enough to keep them there. All seven should have been lost from the cluster within 1,000 years, although the uncertainties remained large for two of them. Based on the size of the cluster, there shouldn’t even be a single foreground star between the Hubble and the Omega Cluster, so these really seem to be within the cluster despite their velocity.

The simplest explanation for that is that there’s an additional mass holding them in place. That could potentially be several massive objects, but the close proximity of all these stars to the center of the cluster favor a single, compact object. Which means a black hole.

Based on the velocities, the researchers estimate that the object has a mass of at least 8,200 times that of the Sun. A couple of stars appear to be accelerating; if that holds up based on further observations, it would indicate that the black hole is over 20,000 solar masses. That places it firmly within black hole territory, though smaller than supermassive black holes, which are viewed as those with roughly a million solar masses or more. And it’s considerably larger than you’d expect from black holes formed through the death of a star, which aren’t expected to be much larger than 100 times the Sun’s mass.

This places it in the category of intermediate-mass black holes, of which there are only a handful of potential sightings, none of them universally accepted. So, this is a significant finding if for no other reason than it may be the least controversial spotting of an intermediate-mass black hole yet.

What’s this telling us?

For now, there are still considerable uncertainties in some of the details here—but prospects for improving the situation exist. Observations with the Webb Space Telescope could potentially pick up the faint emissions from gas that’s falling into the black hole. And it can track the seven stars identified here. Its spectrographs could also potentially pick up the red and blue shifts in light caused by the star’s motion. Its location at a considerable distance from Hubble could also provide a more detailed three-dimensional picture of Omega Centauri’s central structure.

Figuring this out could potentially tell us more about how black holes grow to supermassive scales. Earlier potential sightings of intermediate-mass black holes have also come in globular clusters, which may suggest that they’re a general feature of large gatherings of stars.

But Omega Centauri differs from many other globular clusters, which often contain large populations of stars that all formed at roughly the same time, suggesting the clusters formed from a single giant cloud of materials. Omega Centauri has stars with a broad range of ages, which is one of the reasons why people think it’s the remains of a dwarf galaxy that was sucked into the Milky Way.

If that’s the case, then its central black hole is an analog of the supermassive black holes found in actual dwarf galaxies—which raises the question of why it’s only intermediate-mass. Did something about its interactions with the Milky Way interfere with the black hole’s growth?

And, in the end, none of this sheds light on how any black hole grows to be so much more massive than any star it could conceivably have formed from. Getting a better sense of this black hole’s history could provide more perspective on some questions that are currently vexing astronomers.

Nature, 2024. DOI: 10.1038/s41586-024-07511-z  (About DOIs).

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Swarm of dusty young stars found around our galaxy’s central black hole

astronomy, astrophysics, black holes, milky way, Science, Star formation / /

Hot young stars —

Stars shouldn’t form that close to the black hole, so these would need explaining.

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Image with a black background, large purple streaks, and a handful of bright blue objects.

Enlarge / The Milky Way’s central black hole is in a very crowded neighborhood.

Supermassive black holes are ravenous. Clumps of dust and gas are prone to being disrupted by the turbulence and radiation when they are pulled too close. So why are some of them orbiting on the edge of the Milky Way’s own supermassive monster, Sgr A*? Maybe these mystery blobs are hiding something.

After analyzing observations of the dusty objects, an international team of researchers, led by astrophysicist Florian Peißker of the University of Cologne, have identified these clumps as potentially harboring young stellar objects (YSOs) shrouded by a haze of gas and dust. Even stranger is that these infant stars are younger than an unusually young and bright cluster of stars that are already known to orbit Sgr A*, known as the S-stars.

Finding both of these groups orbiting so close is unusual because stars that orbit supermassive black holes are expected to be dim and much more ancient. Peißker and his colleagues “discard the en vogue idea to classify [these] objects as coreless clouds in the high energetic radiation field of the supermassive black hole Sgr A*,” as they said in a study recently published in Astronomy & Astrophysics.

More than just space dust

To figure out what the objects near Sgr Amight be the, researchers needed to rule out things they weren’t. Embedded in envelopes of gas and dust, they maintain especially high temperatures, do not evaporate easily, and each orbits the supermassive black hole alone.

The researchers determined their chemical properties from the photons they emitted, and their mid- and near-infrared emissions were consistent with those of stars. They used one of them, object G2/DSO, as a case study to test their ideas about what the objects might be. The high brightness and especially strong emissions of this object make it the easiest to study. Its mass is also similar to the masses of known low-mass stars.

YSOs are low-mass stars that have outgrown the protostar phase but have not yet developed into main sequence stars, with cores that fuse hydrogen into helium. These objects like YSO candidates because they couldn’t possibly be clumps of gas and space dust. Gaseous clouds without any objects inside to hold them together via gravity could not survive so close to a supermassive black hole for long. Its intense heat causes the gas and dust to evaporate rather quickly, with heat-excited particles crashing into each other and flying off into space.

The team figured out that a cloud comparable in size to G2/DSO would evaporate in about seven years. A star orbiting at the same distance from the supermassive black hole would not be destroyed nearly as fast because of its much higher density and mass.

Another class of object that the dusty blobs could hypothetically be—but are not—is a compact planetary nebula or CPN. These nebulae are the expanding outer gas envelopes of small to medium stars in their final death throes. While CPNs have some features in common with stars, the strength of a supermassive black hole’s gravity would easily detach their gas envelopes and tear them apart.

It is also unlikely that the YSOs are binary stars, even though most stars form in binary systems. The scorching temperatures and turbulence of SGR Awould likely cause stars that were once part of binaries to migrate.

Seeing stars

Further observations determined that some of the dust-obscured objects are nascent stars, and while others are thought to be stars of some kind, but haven’t been definitively identified.

The properties that made G2/DSO an exceptional case study are also the reason it has been identified as a YSO. D2 is another high-luminosity object about as massive as a low-mass star, which is easy to observe in the near- and mid-infrared. D3 and D23 also have similar properties. These are the blobs near the black hole that the researchers think are most likely to be YSOs.

There are other candidates that need further analysis. These include additional objects that may or may not be YSOs, but still show stellar characteristics: D3.1 and D5, which are difficult to observe. The mid-infrared emissions of D9 are especially low when compared to the other candidates, but it is still thought to be some type of star, though possibly not a YSO. Objects X7 and X8 both exhibit bow shock—the shockwave that results from a star’s stellar wind pushing against other stellar winds. Whether either of these objects is actually a YSO remains unknown.

Where these dusty objects came from and how they formed is unknown for now. The researchers suggest that the objects formed together in molecular clouds that were falling toward the center of the galaxy. They also think that, no matter where they were born, they migrated towards Sgr A*, and any that were in binary systems were separated by the black hole’s immense gravity.

While it is unlikely that the YSOs and potential YSOs originated in the same cluster as the slightly older S-stars, they still might be related in some way. They might have experienced similar formation and migration journeys, and the younger stars might ultimately reach the same stage.

“Speculatively, the dusty sources will evolve into low-mass S stars,” Peißker’s team said in the same study.

Even black holes look better with a necklace of twinkling diamonds.

Astronomy and Astrophysics, 2024.  DOI: 10.1051/0004-6361/202449729

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Saturn’s moon Titan has shorelines that appear to be shaped by waves

astronomy, Cassini, geology, planetary science, Saturn, Science, Titan / /

Surf the moon —

The liquid hydrocarbon waves would likely reach a height of a meter.

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Ligeia Mare, the second-largest body of liquid hydrocarbons on Titan.

Enlarge / Ligeia Mare, the second-largest body of liquid hydrocarbons on Titan.

During its T85 Titan flyby on July 24, 2012, the Cassini spacecraft registered an unexpectedly bright reflection on the surface of the lake Kivu Lacus. Its Visual and Infrared Mapping Spectrometer (VIMS) data was interpreted as a roughness on the methane-ethane lake, which could have been a sign of mudflats, surfacing bubbles, or waves.

“Our landscape evolution models show that the shorelines on Titan are most consistent with Earth lakes that have been eroded by waves,” says Rose Palermo, a coastal geomorphologist at St. Petersburg Coastal and Marine Science Center, who led the study investigating signatures of wave erosion on Titan. The evidence of waves is still inconclusive, but future crewed missions to Titan should probably pack some surfboards just in case.

Troubled seas

While waves have been considered the most plausible explanation for reflections visible in Cassini’s VIMS imagery for quite some time, other studies aimed to confirm their presence found no wave activity at all. “Other observations show that the liquid surfaces have been very still in the past, very flat,” Palermo says. “A possible explanation for this is at the time we were observing Titan, the winds were pretty low, so there weren’t many waves at that time. To confirm waves, we would need to have better resolution data,” she adds.

The problem is that this higher-resolution data isn’t coming our way anytime soon. Dragonfly, the next mission to Titan, isn’t supposed to arrive until 2034, even if everything goes as planned.

To get a better idea about possible waves on Titan a bit sooner, Palermo’s team went for inferring their presence from indirect cues. The researchers assumed shorelines on Titan could have been shaped by one of three candidate scenarios. They first assumed there was no erosion at all; the second modeled uniform erosion caused by the dissolution of the bedrock by the ethane-methane liquid; and the third assumed erosion by wave activity. “We took a random topography with rivers, filled up the basin-flooding river valleys all around the lake. Then, we then used landscape evolution computer model to erode the coast to 50 percent of its original size,” Palermo explains.

Sizing the waves

Palermo’s simulations showed that wave erosion resulted in coastline shapes closely matching those actually observed on Titan.

The team validated its model using data from closer to home. “We compared using the same statistical analysis to lakes on Earth, where we know what the erosion processes are. With certainty greater than 77.5 percent, we were able to predict those known processes with our modeling,” Palermo says.

But even the study that claimed there were waves visible in the Cassini’s VIMS imagery concluded they were roughly 2 centimeters high at best. So even if there are waves on Titan, the question is how high and strong are they?

According to Palermo, wave-generation mechanisms on Titan should work just like they do on Earth, with some notable differences. “There is a difference in viscosity between water on Earth and methane-ethane liquid on Titan compared to the atmosphere,” says Palermo. The gravity is also a lot weaker, standing at only one-seventh of the gravity on Earth. “The gravity, along with the differences in material properties, contributes to the waves being taller and steeper than those on Earth for the same wind speed,” says Palermo.

But even with those boosts to size and strength, could waves on Titan actually be any good for surfing?

Surf’s up

“There are definitely a lot of open questions our work leads to. What is the direction of the dominant waves? Knowing that can tell us about the winds and, therefore, about the climate on Titan. How large do the waves get? In the future, maybe we could tell that with modeling how much erosion occurs in one part of the lake versus another in estimated timescales. There is a lot more we could learn,” Palermo says. As far as surfing is concerned, she said that, assuming a minimum height for a surfable wave of around 15 centimeters, surfing on Titan should most likely be doable.

The key limit on the size and strength of any waves on Titan is that most of its seas are roughly the size of the Great Lakes in the US. The largest of them, the Kraken Mare, is roughly as large as the Caspian Sea on Earth. There is no such thing as a global ocean on Titan, and this means the fetch, the distance over which the wind can blow and grow the waves, is limited to tens of kilometers instead of over 1,500 kilometers on Earth. “Still, some models show that the waves on Titan be as high as one meter. I’d say that’s a surfable wave,” Palermo concluded.

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Astronomers think they’ve figured out how and when Jupiter’s Red Spot formed

astronomy, geophysics, Giovanni Cassini, great red spot, Jupiter, Science, science history / /

a long-lived vortex —

Astronomers concluded it is not the same and that Cassini’s spot disappeared in 1708.

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Enhanced image of Jupiter’s Great Red Spot, as seen from a Juno flyby in 2018. The Red Spot we see today is likely not the same one famously observed by Cassini in the 1600s.

Enlarge / Enhanced Juno image of Jupiter’s Great Red Spot in 2018. It is likely not the same one observed by Cassini in the 1600s.

The planet Jupiter is particularly known for its so-called Great Red Spot, a swirling vortex in the gas giant’s atmosphere that has been around since at least 1831. But how it formed and how old it is remain matters of debate. Astronomers in the 1600s, including Giovanni Cassini, also reported a similar spot in their observations of Jupiter that they dubbed the “Permanent Spot.” This prompted scientists to question whether the spot Cassini observed is the same one we see today. We now have an answer to that question: The spots are not the same, according to a new paper published in the journal Geophysical Research Letters.

“From the measurements of sizes and movements, we deduced that it is highly unlikely that the current Great Red Spot was the ‘Permanent Spot’ observed by Cassini,” said co-author Agustín Sánchez-Lavega of the University of the Basque Country in Bilbao, Spain. “The ‘Permanent Spot’ probably disappeared sometime between the mid-18th and 19th centuries, in which case we can now say that the longevity of the Red Spot exceeds 190 years.”

The planet Jupiter was known to Babylonian astronomers in the 7th and 8th centuries BCE, as well as to ancient Chinese astronomers; the latter’s observations would eventually give birth to the Chinese zodiac in the 4th century BCE, with its 12-year cycle based on the gas giant’s orbit around the Sun. In 1610, aided by the emergence of telescopes, Galileo Galilei famously observed Jupiter’s four largest moons, thereby bolstering the Copernican heliocentric model of the solar system.

(a) 1711 painting of Jupiter by Donato Creti showing the reddish Permanent Spot. (b) November 2, 1880, drawing of Jupiter by E.L. Trouvelot. (c) November 28, 1881, drawing by T.G. Elger.

Enlarge / (a) 1711 painting of Jupiter by Donato Creti showing the reddish Permanent Spot. (b) November 2, 1880, drawing of Jupiter by E.L. Trouvelot. (c) November 28, 1881, drawing by T.G. Elger.

Public domain

It’s possible that Robert Hooke may have observed the “Permanent Spot” as early as 1664, with Cassini following suit a year later and multiple more sightings through 1708. Then it disappeared from the astronomical record. A pharmacist named Heinrich Schwabe made the earliest known drawing of the Red Spot in 1831, and by 1878 it was once again quite prominent in observations of Jupiter, fading again in 1883 and at the onset of the 20th century.

Perhaps the spot is not the same…

But was this the same Permanent Spot that Cassini had observed? Sánchez-Lavega and his co-authors set out to answer this question, combing through historical sources—including Cassini’s notes and drawings from the 17th century—and more recent astronomical observations and quantifying the results. They conducted a year-by-year measurement of the sizes, ellipticity, area, and motions of both the Permanent Spot and the Great Red Spot from the earliest recorded observations into the 21st century.

The team also performed multiple numerical computer simulations testing different models for vortex behavior in Jupiter’s atmosphere that are the likely cause of the Great Red Spot. It’s essentially a massive, persistent anticyclonic storm. In one of the models the authors tested, the spot forms in the wake of a massive superstorm. Alternatively, several smaller vortices created by wind shear may have merged, or there could have been an instability in the planet’s wind currents that resulted in an elongated atmospheric cell shaped like the spot.

Sánchez-Lavega et al. concluded that the current Red Spot is probably not the same as that observed by Cassini and others in the 17th century. They argue that the Permanent Spot had faded by the start of the 18th century, and a new spot formed in the 19th century—the one we observe today, making it more than 190 years old.

Comparison between the Permanent Spot and the current Great Red Spot. (a) December 1690. (b) January 1691. (c) January 19, 1672. (d) August 10, 2023.

Enlarge / Comparison between the Permanent Spot and the current Great Red Spot. (a) December 1690. (b) January 1691. (c) January 19, 1672. (d) August 10, 2023.

Public domain/Eric Sussenbach

But maybe it is?

Others remain unconvinced of that conclusion, such as astronomer Scott Bolton of the Southwest Research Institute in Texas. “What I think we may be seeing is not so much that the storm went away and then a new one came in almost the same place,” he told New Scientist. “It would be a very big coincidence to have it occur at the same exact latitude, or even a similar latitude. It could be that what we’re really watching is the evolution of the storm.”

The numerical simulations ruled out the merging vortices model for the spot’s formation; it is much more likely that it’s due to wind currents producing an elongated atmospheric shell. Furthermore, in 1879, the Red Spot measured about 24,200 miles (39,000 kilometers) at its longest axis and is now about 8,700 miles (14,000 kilometers). So, the spot has been shrinking over the ensuing decades and becoming more rounded. The Juno mission’s most recent observations also revealed the spot is thin and shallow.

The question of why the Great Red Spot is shrinking remains a matter of debate. The team plans further simulations aiming to reproduce the shrinking dynamics and predict whether the spot will stabilize at a certain size and remain stable or eventually disappear like Cassini’s Permanent Spot presumably did.

Geophysical Research Letters, 2024. DOI: 10.1029/2024GL108993  (About DOIs).

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Supermassive black hole roars to life as astronomers watch in real time

active galactic nuclei, astronomy, astrophysics, black holes, Physics, Science, Very Large Telescope / /

Sleeping Beauty —

A similar awakening may one day occur with the Milky Way’s supermassive black hole

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Artist’s animation of the black hole at the center of SDSS1335+0728 awakening in real time—a first for astronomers.

In December 2019, astronomers were surprised to observe a long-quiet galaxy, 300 million light-years away, suddenly come alive, emitting ultraviolet, optical, and infrared light into space. Far from quieting down again, by February of this year, the galaxy had begun emitting X-ray light; it is becoming more active. Astronomers think it is most likely an active galactic nucleus (AGN), which gets its energy from supermassive black holes at the galaxy’s center and/or from the black hole’s spin. That’s the conclusion of a new paper accepted for publication in the journal Astronomy and Astrophysics, although the authors acknowledge the possibility that it might also be some kind of rare tidal disruption event (TDE).

The brightening of SDSS1335_0728 in the constellation Virgo, after decades of quietude, was first detected by the Zwicky Transient Facility telescope. Its supermassive black hole is estimated to be about 1 million solar masses. To get a better understanding of what might be going on, the authors combed through archival data and combined that with data from new observations from various instruments, including the X-shooter, part of the Very Large Telescope (VLT) in Chile’s Atacama Desert.

There are many reasons why a normally quiet galaxy might suddenly brighten, including supernovae or a TDE, in which part of the shredded star’s original mass is ejected violently outward. This, in turn, can form an accretion disk around the black hole that emits powerful X-rays and visible light. But these events don’t last nearly five years—usually not more than a few hundred days.

So the authors concluded that the galaxy has awakened and now has an AGN. First discovered by Carl Seyfert in 1943, the glow is the result of the cold dust and gas surrounding the black hole, which can form orbiting accretion disks. Gravitational forces compress the matter in the disk and heat it to millions of degrees Kelvin, producing radiation across the electromagnetic spectrum.

Alternatively, the activity might be due to an especially long and faint TDE—the longest and faintest yet detected, if so. Or it could be an entirely new phenomenon altogether. So SDSS1335+0728 is a galaxy to watch. Astronomers are already preparing for follow-up observations with the VLT’s Multi Unit Spectroscopic Explorer (MUSE) and Extremely Large Telescope, among others, and perhaps even the Vera Rubin Observatory slated to come online next summer. Its Large Synoptic Survey Telescope (LSST) will be capable of imaging the entire southern sky continuously, potentially capturing even more galaxy awakenings.

“Regardless of the nature of the variations, [this galaxy] provides valuable information on how black holes grow and evolve,” said co-author Paula Sánchez Sáez, an astronomer at the European Southern Observatory in Germany. “We expect that instruments like [these] will be key in understanding [why the galaxy is brightening].”

There is also a supermassive black hole at the center of our Milky Way galaxy (Sgr A*), but there is not yet enough material that has accreted for astronomers to pick up any emitted radiation, even in the infrared. So, its galactic nucleus is deemed inactive. It may have been active in the past, and it’s possible that it will reawaken again in a few million (or even billion) years when the Milky Way merges with the Andromeda Galaxy and their respective supermassive black holes combine. Only much time will tell.

Astronomy and Astrophysics, 2024. DOI: 10.1051/0004-6361/202347957  (About DOIs).

Listing image by ESO/M. Kornmesser

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Polarized light yields fresh insight into mysterious fast radio bursts

astronomy, astrophysics, CHIME, fast radio bursts, Physics, Science / /

CHIME-ing in —

Scientists looked at how polarization changed direction to learn more about origins

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Artist’s rendition of how the angle of polarized light from an FRB changes as it journeys through space.

Enlarge / Artist’s rendition of how the angle of polarized light from a fast radio burst changes as it journeys through space.

CHIME/Dunlap Institute

Astronomers have been puzzling over the origins of mysterious fast radio bursts (FRBs) since the first one was spotted in 2007. Researchers now have their first look at non-repeating FRBs, i.e., those that have only produced a single burst of light to date. The authors of a new paper published in The Astrophysical Journal looked specifically at the properties of polarized light emitting from these FRBs, yielding further insight into the origins of the phenomenon. The analysis supports the hypothesis that there are different origins for repeating and non-repeating FRBs.

“This is a new way to analyze the data we have on FRBs. Instead of just looking at how bright something is, we’re also looking at the angle of the light’s vibrating electromagnetic waves,” said co-author Ayush Pandhi, a graduate student at the University of Toronto’s Dunlap Institute for Astronomy and Astrophysics. “It gives you additional information about how and where that light is produced and what it has passed through on its journey to us over many millions of light years.”

As we’ve reported previously, FRBs involve a sudden blast of radio-frequency radiation that lasts just a few microseconds. Astronomers have over a thousand of them to date; some come from sources that repeatedly emit FRBs, while others seem to burst once and go silent. You can produce this sort of sudden surge of energy by destroying something. But the existence of repeating sources suggests that at least some of them are produced by an object that survives the event. That has led to a focus on compact objects, like neutron stars and black holes—especially a class of neutron stars called magnetars—as likely sources.

There have also been many detected FRBs that don’t seem to repeat at all, suggesting that the conditions that produced them may destroy their source. That’s consistent with a blitzar—a bizarre astronomical event caused by the sudden collapse of an overly massive neutron star. The event is driven by an earlier merger of two neutron stars; this creates an unstable intermediate neutron star, which is kept from collapsing immediately by its rapid spin.

In a blitzar, the strong magnetic fields of the neutron star slow down its spin, causing it to collapse into a black hole several hours after the merger. That collapse suddenly deletes the dynamo powering the magnetic fields, releasing their energy in the form of a fast radio burst.

So the events we’ve been lumping together as FRBs could actually be the product of two different events. The repeating events occur in the environment around a magnetar. The one-shot events are triggered by the death of a highly magnetized neutron star within a few hours of its formation. Astronomers announced the detection of a possible blitzar potentially associated with an FRB last year.

Only about 3 percent of FRBs are of the repeating variety. Per Pandhi, this is the first analysis of the other 97 percent of non-repeating FRBs, using data from Canada’s CHIME instrument (Canadian Hydrogen Intensity Mapping Experiment). CHIME was built for other observations but is sensitive to many of the wavelengths that make up an FRB. Unlike most radio telescopes, which focus on small points in the sky, CHIME scans a huge area, allowing it to pick out FRBs even though they almost never happen in the same place twice.

Pandhi et al. decided to investigate how the direction of the light polarization from 128 non-repeating FRBs changes to learn more about the environments in which they originated. The team found that the polarized light from non-repeating FRBs changes both with time and with different colors of light. They concluded that this particular sample of non-repeating FRBs is either a separate population or more evolved versions of these kinds of FRBs that are part of a population that originated in less extreme environments with lower burst rates. That’s in keeping with the notion that non-repeating FRBs are quite different from their rarer repeating FRBs.

The Astrophysical Journal, 2024. DOI: 10.3847/1538-4357/ad40aa  (About DOIs).

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Radio telescope finds another mystery long-repeat source

astronomy, astrophysics, neutron stars, pulsars, Science, weird stuff / /

File under W for WTF —

Unlike earlier object, the new source’s pulses of radio waves are erratic.

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Image of a purple, glowing sphere with straight purple-white lines emerging from opposite sides, all against a black background.

Enlarge / A slowly rotating neutron star is still our best guess as to the source of the mystery signals.

Roughly a year ago, astronomers announced that they had observed an object that shouldn’t exist. Like a pulsar, it emitted regularly timed bursts of radio emissions. But unlike a pulsar, those bursts were separated by over 20 minutes. If the 22 minute gap between bursts represents the rotation period of the object, then it is rotating too slowly to produce radio emissions by any known mechanism.

Now, some of the same team (along with new collaborators) are back with the discovery of something that, if anything, is acting even more oddly. The new source of radio bursts, ASKAP J193505.1+214841.0, takes nearly an hour between bursts. And it appears to have three different settings, sometimes producing weaker bursts and sometimes skipping them entirely. While the researchers suspect that, like pulsars, this is also powered by a neutron star, it’s not even clear that it’s the same class of object as their earlier discovery.

How pulsars pulse

Contrary to the section heading, pulsars don’t actually pulse. Neutron stars can create the illusion by having magnetic poles that aren’t lined up with their rotational pole. The magnetic poles are a source of constant radio emissions but, as the neutron star rotates, the emissions from the magnetic pole sweep across space in a manner similar to the light from a rotating lighthouse. If Earth happens to be caught up in that sweep, then the neutron star will appear to blink on and off as it rotates.

The star’s rotation is also needed for the generation of radio emissions themselves. If the neutron star rotates too slowly, then its magnetic field won’t be strong enough to produce radio emissions. So, it’s thought that if a pulsar’s rotation slows down enough (causing its pulses to be separated by too much time), it will simply shut down, and we’ll stop observing any radio emissions from the object.

We don’t have a clear idea of how long the time between pulses can get before a pulsar will shut down. But we do know that it’s going to be far less than 22 minutes.

Which is why the 2023 discovery was so strange. The object, GPM J1839–10, not only took a long time between pulses, but archival images showed that it had been pulsing on and off since at least 35 years ago.

To figure out what is going on, we really have two options. One is more and better observations of the source we know about. The second is to find other examples of similar behavior. There’s a chance we now have a second object like this, although there are enough differences that it’s not entirely clear.

An enigmatic find

The object, ASKAPJ193505.1+214841.0, was discovered by accident when the Australian Square Kilometre Array Pathfinder telescope was used to perform observations in the area due to detections of a gamma ray burst. It picked up a bright radio burst in the same field of view, but unrelated to the gamma ray burst. Further radio bursts showed up in later observations, as did a few far weaker bursts. A search of the telescope’s archives also spotted a weaker burst from the same location.

Checking the timing of the radio bursts, the team found that they could be explained by an object that emitted bursts every 54 hours, with bursts lasting from 10 seconds to just under a minute. Checking additional observations, however, showed that there were often instances where a 54 minute period would not end with a radio burst, suggesting the source sometimes skipped radio emissions entirely.

Odder still, the photons in the strong and weak bursts appeared to have different polarizations. These differences arise from the magnetic fields present where the bursts originate, suggesting that the two types of bursts differ not only in total energy, but also that the object that’s making them has a different magnetic field.

So, the researchers suggest that the object has three modes: strong pulses, faint pulses, and an off mode, although they can’t rule out the off mode producing weak radio signals that are below the detection capabilities of the telescopes we’re using. Over about eight months of sporadic observations, there’s no apparent pattern to the bursts.

What is this thing?

Checks at other wavelengths indicate there’s a magnetar and a supernova remnant in the vicinity of the mystery object, but not at the same location. There’s also a nearby brown dwarf at that point in the sky, but they strongly suspect that’s just a chance overlap. So, none of that tells us more about what produces these erratic bursts.

As with the earlier find, there seem to be two possible explanations for the ASKAP source. One is a neutron star that’s still managing to emit radiofrequency radiation from its poles despite rotating extremely slowly. The second is a white dwarf that has a reasonable rotation period but an unreasonably strong magnetic field.

To get at this issue, the researchers estimate the strength of the magnetic field needed to produce the larger bursts and come up with a value that’s significantly higher than any previously observed to originate on a white dwarf. So they strongly argue for the source being a neutron star. Whether that argues for the earlier source being a neutron star will depend on whether you feel that the two objects represent a single phenomenon despite their somewhat different behaviors.

In any case, we now have two of these mystery slow-repeat objects to explain. It’s possible that we’ll be able to learn more about this newer one if we can get some information as to what’s involved in its mode switching. But then we’ll have to figure out if what we learn applies to the one we discovered earlier.

Nature Astronomy, 2024. DOI: 10.1038/s41550-024-02277-w  (About DOIs).

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Nova explosion visible to the naked eye expected any day now

astronomy, astrophysics, nova, Science, white dwarf / /
Image of a blue sphere, surrounded by blue filaments, and enclosed in a partial sphere of pink specks.s

Enlarge / Aftermath of a nova at the star GK Persei.

When you look at the northern sky, you can follow the arm of the Big Dipper as it arcs around toward the bright star called Arcturus. Roughly in the middle of that arc, you’ll find the Northern Crown constellation, which looks a bit like a smiley face. Sometime between now and September, if you look to the left-hand side of the Northern Crown, what will look like a new star will shine for five days or so.

This star system is called T. Coronae Borealis, also known as the Blaze Star, and most of the time, it is way too dim to be visible to the naked eye. But once roughly every 80 years, a violent thermonuclear explosion makes it over 10,000 times brighter. The last time it happened was in 1946, so now it’s our turn to see it.

Neighborhood litterbug

“The T. Coronae Borealis is a binary system. It is actually two stars,” said Gerard Van Belle, the director of science at Lowell Observatory in Flagstaff, Arizona. One of these stars is a white dwarf, an old star that has already been through its fusion-powered lifecycle. “It’s gone from being a main sequence star to being a giant star. And in the case of giant stars, what happens is their outer parts eventually get kind of pushed into outer space. What’s left behind is a leftover core of the star—that’s called a white dwarf,” Van Belle explained.

The white dwarf stage is normally a super peaceful retirement period for stars. The nuclear fusion reaction no longer takes place, which makes white dwarfs very dim. They are still pretty hot, though, and they’re super dense, with a mass comparable to our Sun squeezed into a volume resembling the Earth.

But the retirement of the white dwarf in T. Coronae Borealis is hardly peaceful, as it has a neighbor prone to littering. “Its companion star is in the red giant phase, where it is puffed up. Its outer parts are getting sloughed off and pushed into space. The material that is coming off the red giant is now falling onto the white dwarf,” Van Belle said.

Ticking time bomb

And it doesn’t take much littering to make the white dwarf explode. “The material from the red giant will accumulate on the white dwarf’s surface until it forms a layer that’s actually not that thick. Just a few meters—the depth of a deep swimming pool,” Van Belle explained. Most of the material coming off the red giant is hydrogen. And since the red dwarf is still hot, there will eventually be a spark that triggers a runaway nuclear fusion reaction. “That is what causes the explosion,” Van Belle said.

The explosion is a nova, which means it doesn’t kill either the white dwarf or the red giant as a supernova would. “Only about 5 percent of the hydrogen layer fuses into heavier elements like helium, and the rest just gets ejected into space. Then the process starts all over again because the explosion isn’t large enough to disrupt the red giant, the donor of all this hydrogen, so it just keeps doing its thing,” Van Belle told Ars. This is why we can predict this event with such precision.

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How the perils of space have affected asteroid Ryugu

asteroid, astronomy, magneticsm, planetary science, Ryugu, Science / /

Magnets: how do they stop working? —

Ryugu’s parent body appears to have had a fair amount of water present, too.

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Grey image of a complicated surface composed of many small rocks bound together by dust.

Enlarge / The surface of Ryugu. Image credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, Aizu University, AIST

An asteroid that has been wandering through space for billions of years is going to have been bombarded by everything from rocks to radiation. Billions of years traveling through interplanetary space increase the odds of colliding with something in the vast emptiness, and at least one of those impacts had enough force to leave the asteroid Ryugu forever changed.

When the Japanese Space Agency’s Hayabusa2 spacecraft touched down on Ryugu, it collected samples from the surface that revealed that particles of magnetite (which is usually magnetic) in the asteroid’s regolith are devoid of magnetism. A team of researchers from Hokkaido University and several other institutions in Japan are now offering an explanation for how this material lost most of its magnetic properties. Their analysis showed that it was caused by at least one high-velocity micrometeoroid collision that broke the magnetite’s chemical structure down so that it was no longer magnetic.

“We surmised that pseudo-magnetite was created [as] the result of space weathering by micrometeoroid impact,” the researchers, led by Hokkaido University professor Yuki Kimura, said in a study recently published in Nature Communications.

What remains…

Ryugu is a relatively small object with no atmosphere, which makes it more susceptible to space weathering—alteration by micrometeoroids and the solar wind. Understanding space weathering can actually help us understand the evolution of asteroids and the Solar System. The problem is that most of our information about asteroids comes from meteorites that fall to Earth, and the majority of those meteorites are chunks of rock from the inside of an asteroid, so they were not exposed to the brutal environment of interplanetary space. They can also be altered as they plummet through the atmosphere or by physical processes on the surface. The longer it takes to find a meteorite, the more information can potentially be lost.

Once part of a much larger body, Ryugu is a C-type, or carbonaceous, asteroid, meaning it is made of mostly clay and silicate rocks. These minerals normally need water to form, but their presence is explained by Ryugu’s history. It is thought that the asteroid itself was born from debris after its parent body was smashed to pieces in a collision. The parent body was also covered in water ice, which explains the magnetite, carbonates, and silicates found on Ryugu—these need water to form.

Magnetite is a ferromagnetic (iron-containing and magnetic) mineral. It is found in all C-type asteroids and can be used to determine their remanent, or remaining, magnetization. The remanent magnetization of an asteroid can reveal how intense the magnetic field was at the time and place of the magnetite’s formation.

Kimura and his team were able to measure remanent magnetization in two magnetite fragments (known as framboids because of their particular shape) from the Ryugu sample. It is proof of a magnetic field in the nebula our Solar System formed in, and shows the strength of that magnetic field at the time that the magnetite formed.

However, three other magnetite fragments analyzed were not magnetized at all. This is where space weathering comes in.

…and what was lost

Using electron holography, which is done with a transmission electron microscope that sends high-energy electron waves through a specimen, the researchers found that the three framboids in question did not have magnetic chemical structures. This made them drastically different from magnetite.

Further analysis with scanning transmission electron microscopy showed that the magnetite particles were mostly made of iron oxides, but there was less oxygen in those particles that had lost their magnetism, indicating that the material had experienced a chemical reduction, where electrons were donated to the system. This loss of oxygen (and oxidized iron) explained the loss of magnetism, which depends on the organization of the electrons in the magnetite. This is why Kimura refers to it as “pseudo-magnetite.”

But what triggered the reduction that demagnetized the magnetite in the first place? Kimura and his team found that there were more than a hundred metallic iron particles in the part of the specimen that the demagnetized framboids had come from. If a micrometeorite of a certain size had hit that region of Ryugu then it would have produced approximately that many particles of iron from the magnetite framboids. The researchers think this mystery object was rather small, or it would have had to have been moving incredibly fast.

“With increasing impact velocity, the estimated projectile size decreases,” they said in the same study.

Pseudo-magnetite might sound like an imposter, but it will actually help upcoming investigations that seek to find out more about what the early Solar System was like. Its presence indicates the former presence of water on an asteroid, as well as space weathering, such as micrometeoroid bombardment, that affected the asteroid’s composition. How much magnetism was lost also affects the overall remanence of the asteroid. Remanence is important in determining an object’s magnetism and the intensity of the magnetic field around it when it formed. What we know of the Solar System’s early magnetic field has been reconstructed from remanence records, many of which come from magnetite.

Some magnetic properties of those particles might have been lost eons ago, but so much more could be gained in the future from what remains.

Nature Communications, 2024.  DOI: 10.1038/s41467-024-47798-0

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Monster galactic outflow powered by exploding stars

astronomy, astrophysics, galaxy evolution, Science / /

A big burp —

Star death and birth both contribute to driving material out of a galaxy.

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Image of a galaxy showing lots of complicated filaments of gas.

Enlarge / All galaxies have large amounts of gas that influence their star-formation rates.

Galaxies pass gas—in the case of galaxy NGC 4383, so much so that its gas outflow is 20,000 light-years across and more massive than 50 million Suns.

Yet even an outflow of this immensity was difficult to detect until now. Observing what these outflows are made of and how they are structured demands high-resolution instruments that can only see gas from galaxies that are relatively close, so information on them has been limited. Which is unfortunate, since gaseous outflows ejected from galaxies can tell us more about their star formation cycles.

The MAUVE (MUSE and ALMA Unveiling the Virgo Environment) program is now changing things. MAUVE’s mission is to understand how the outflows of galaxies in the Virgo cluster affect star formation. NGC 4383 stood out to astronomer Adam Watts, of the University of Australia and the International Centre for Radio Astronomy Research (ICRAR), and his team because its outflow is so enormous.

The elements it releases into space can reveal the galaxy’s potential to form (or stop forming) stars. “Understanding the physics of stellar feedback-driven outflows… is essential to completing our picture of galaxy evolution,” the researchers said in a study recently published in Monthly Notices of the Royal Astronomical Society.

Star potential

Stellar feedback, which is all the radiation, particle winds, and other materials that stars blast into the interstellar medium, is what forms outflows as huge as that in NGC 4383. Much of this material comes from either bursts of star formation or the insides of massive stars when they die and go supernova. It includes heavier elements that escape into space with the outflow and float there for an indefinite amount of time, sometimes ending up in other galaxies.

Star formation in a galaxy depends on several processes. There has to be the right balance of gas accretion (growth from added gas), consumption (the burning of hydrogen and helium by stars), and ejection (when interstellar gas is blown out of the galaxy) between the intergalactic medium and circumgalactic medium, the gas surrounding galaxies. Some of the gas and other materials, such as iron and other heavy elements, that form stars can be recycled from supernova explosions.

The supply of gas is key because large amounts of gas eventually collapse in on themselves because of their immense gravity, eventually forming stars. A deficit of gas can squelch the formation of potential stars.

Watts and his team think that one source of the stellar feedback pushing star-forming gas out of NGC 4383 is multiple supernovae that occurred relatively close together. Supernovae can form gargantuan bubbles of scorching gas that eventually break out of a galactic disk vertically, extending from the top and bottom of the galaxy.

Hot gas continues into cooler regions of the interstellar medium, with its gravity pulling in more gas on the way out of the galaxy and increasing the total mass of the outflow (known as mass loading). The loss of so much gas decreases the chances of star formation even further.

Lost in space

Outflows can be observed at many different wavelengths. Emissions of X-rays from elements such as hydrogen and compounds such as carbon monoxide can be detected. It is also possible to observe outflows using UV, optical, and infrared. Some of the region’s emissions had already been observed with other telescopes, which was combined with MAUVE imaging of the Virgo Cluster and NGC 4383 at different wavelengths.

The problem with observing outflows accurately is that the scattered materials are notoriously difficult to spatially resolve, which means figuring out the distance of the entire outflow based on pixels. MAUVE, NGC 4383, and the Virgo Cluster were observed at a spatial resolution of about 261 light-years, so each pixel represented a square in space that measured 261 light-years on every side. Clumps of ionized gas that showed up in these pixels told the research team there was a bipolar outflow leaving the galaxy from the top and bottom.

So, does NGC 4383 have reduced star formation because of its massive outflow of star stuff? It turns out that stars are actually forming at the galaxy’s edge. While no stars form in the stream escaping the galaxy, there are still areas where there is enough accreted gas to give birth to them.

These starbursts, or areas of rapid star formation, are also providing stellar feedback—it’s not just supernovae. “There is an extension of blue knots that are much brighter in the near-UV and are clear evidence of star formation occurring outside the main body of the galaxy,” the researchers said in the same study.

Something that remains unclear about NGC 4383 is whether the gas outflow was set off by stellar feedback alone or whether a gravitational interaction with another galaxy intensified existing outflows. There is possibly evidence for this on the eastern side, where a disturbance in the gas suggests that a nearby dwarf galaxy might have interacted with it. For now, the research team is confident that the outflow is primarily driven by starbursts and supernovae.

There is still more that the researchers want to find out about NGC 4383 and its outflow. As telescopes become more advanced and spatial resolution improves, maybe something else will be revealed inside those clouds of gas.

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Glow of an exoplanet may be from starlight reflecting off liquid iron

astronomy, atmospheres, exoplanets, Science / /

For all the glory —

A phenomenon called a “glory” may be happening on a hellishly hot giant planet.

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Image of a planet on a dark background, with an iridescent circle on the right side of the planet.

Enlarge / Artist impression of a glory on exoplanet WASP-76b.

Do rainbows exist on distant worlds? Many phenomena that happen on Earth—such as rain, hurricanes, and auroras—also occur on other planets in our Solar System if the conditions are right. Now we have evidence from outside our Solar System that one particularly strange exoplanet might even be displaying something close to a rainbow.

Appearing in the sky as a halo of colors, a phenomenon called a “glory” occurs when light hits clouds made up of a homogeneous substance in the form of spherical droplets. It might be the explanation for a mystery regarding observations of exoplanet WASP-76B. This planet, a scorching gas giant that experiences molten iron rain, has also been observed to have more light on its eastern terminator (a line used to separate the day side from the night side) than its western terminator. Why was there more light on one side of the planet?

After observing it with the CHEOPS space telescope, then combining that with previous observations from Hubble, Spitzer, and TESS, a team of researchers from ESA and the University of Bern in Switzerland now think that the most likely reason for the extra light is a glory.

Seeing the light

Over three years, CHEOPS made 23 observations of WASP-76B in both visible and infrared light. These included phase curves, transits, and secondary eclipses. Phase curves are continuous observations that track a planet’s complete revolution and show changes in its phase or the part of its illuminated side that is facing the telescope. The telescope may see more or less of that side as the planet orbits its star. Phase curves can determine the change in the total brightness of the planet and star as the planet orbits.

Secondary eclipses happen when a planet passes behind its host star and is eclipsed by it. The light seen during such an eclipse can later be compared with the total light both before and after the occultation to give us a sense of the light that’s reflected off the planet. Hot Jupiters like WASP-76B are commonly observed through secondary eclipses.

Phase-curve observations can continue while the planet is eclipsing its star. While it was observing the phase curve of WASP-76B, CHEOPS saw a pre-eclipse excess of light on its night side. This had also been seen in TESS phase-curve and secondary-eclipse observations that had been made earlier.

End of the rainbow?

An advantage of WASP-76b is that it is an ultra-hot Jupiter, so at least its day side does not have the clouds and hazes that often obscure the atmospheres of cooler hot Jupiters. This makes atmospheric emissions much easier to detect. That we had already observed an asymmetry in iron content between the day-side and night-side terminators, discovered in a previous study, made the planet especially intriguing. There was not much gaseous iron in the upper atmosphere of the day-side limb compared to that of the night-side limb. This is probably because it rains iron on the day side of WASP-76b, which then condenses into clouds of iron on the night side.

Observations from Hubble suggested that thermal inversion—when the air near the surface of a planet begins cooling—was occurring on the night side. Cooling on that side would cause iron that had previously condensed into clouds, rained down onto the day side, and then evaporated from the intense heat to condense again. Drops of liquid iron can then form clouds.

These clouds are critical since light from the host star, reflecting off these drops in those clouds, can create the effect of a glory.

“Explaining the observation with the glory effect would require spherical droplets of highly reflective, spherically shaped aerosols and clouds on the planet’s eastern hemisphere,” the researchers said in a paper recently published in Astronomy & Astrophysics.

Glories have been seen off Earth before. They are also known to form in the clouds of Venus. Just like WASP-76b, more pre-eclipse light was observed on Venus, so while a glory is all but definite for the exoplanet, future observations with a more powerful telescope could help determine how similar the phenomenon on WASP-76 is to that on Venus. If they match, this will be the first glory ever observed on an exoplanet.

If future research figures out a definite way to tell whether this is really a glory, these phenomena could tell us more about the atmospheric makeup of exoplanets, depending on the kinds of elements or molecules light is reflecting off of. They might even give away the presence of water, which could mean habitability. While the hypothesized glory on WASP-76b has not been definitively demonstrated, it is anything but a rainbow in the dark.

Astronomy & Astrophysics, 2024. DOI: 10.1051/0004-6361/202348270

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