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      A star nicknamed ‘Earendel’ may be the most distant yet seen

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      A chance alignment may have revealed a star from the universe’s first billion years.

      If confirmed, this star would be the most distant one ever seen, obliterating the previous record (SN: 7/11/17). Light from the star traveled for about 12.9 billion years on its journey toward Earth, about 4 billion years longer than the former record holder, researchers report in the March 30 Nature. Studying the object could help researchers learn more about the universe’s composition during that early, mysterious time.

      “These are the sorts of things that you only hope you could discover,” says astronomer Katherine Whitaker of the University of Massachusetts Amherst, who was not part of the new study.

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      The researchers found the object while analyzing Hubble Space Telescope images of dozens of clusters of galaxies nearer to Earth. These clusters are so massive that they bend and focus the light from more distant background objects, what’s known as gravitational lensing (SN: 10/6/15).

      In images of one cluster, astronomer Brian Welch of Johns Hopkins University and colleagues noticed a long, thin, red arc. The team realized that the arc was a background galaxy whose light the cluster had warped and amplified.

      Atop that red arc is a bright spot that is too small to be a small galaxy or a star cluster, the researchers say. “We stumbled into finding that this was a lensed star,” Welch says.

      The researchers estimate that the star’s light originates from only 900 million years after the Big Bang, which took place about 13.8 billion years ago.

      Welch and his colleagues think that the object, which they poetically nicknamed “Earendel” from the old English word meaning “morning star” or “rising light,” is a behemoth with at least 50 times the mass of the sun. But the researchers can’t pin down that value, or learn more about the star or even confirm that it is a star, without more detailed observations.

      The researchers plan to use the recently launched James Webb Space Telescope to examine Earendel (SN: 10/6/21). The telescope, also known as JWST, will begin studying the distant universe this summer.

      JWST may uncover objects from even earlier times in the universe’s history than what Hubble can see because the new telescope will be sensitive to light from more distant objects. Welch hopes that the telescope will find many more of these gravitationally lensed stars. “I’m hoping that this record won’t last very long.” More

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      Binary stars keep masquerading as black holes

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      As astronomy datasets grow larger, scientists are scouring them for black holes, hoping to better understand the exotic objects. But the drive to find more black holes is leading some astronomers astray.

      “You say black holes are like a needle in a haystack, but suddenly we have way more haystacks than we did before,” says astrophysicist Kareem El-Badry of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “You have better chances of finding them, but you also have more opportunities to find things that look like them.”

      Two more claimed black holes have turned out to be the latter: weird things that look like them. They both are actually double-star systems at never-before-seen stages in their evolutions, El-Badry and his colleagues report March 24 in Monthly Notices of the Royal Astronomical Society. The key to understanding the systems is figuring out how to interpret light coming from them, the researchers say.  

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      In early 2021, astronomer Tharindu Jayasinghe of Ohio State University and his colleagues reported finding a star system — affectionately named the Unicorn — about 1,500 light-years from Earth that they thought held a giant red star in its senior years orbiting an invisible black hole. Some of the same researchers, including Jayasinghe, later reported a second similar system, dubbed the Giraffe, found about 12,000 light-years away.

      But other researchers, including El-Badry, weren’t convinced that the systems harbored black holes. So Jayasinghe, El-Badry and others combined forces to reanalyze the data.

      To verify each star system’s nature, the researchers turned to stellar spectra, the rainbows that are produced when starlight is split up into its component wavelengths. Any star’s spectrum will have lines where atoms in the stellar atmosphere have absorbed particular wavelengths of light. A slow-spinning star has very sharp lines, but a fast-spinning one has blurred and smeared lines.

      “If the star spins fast enough, basically all the spectral features become almost invisible,” El-Badry says. “Normally, you detect a second star in a spectrum by looking for another set of lines,” he adds. “And that’s harder to do if a star is rapidly rotating.”

      That’s why Jayasinghe and colleagues misunderstood each of these systems initially, the team found.

      “The problem was that there was not just one star, but a second one that was basically hiding,” says astrophysicist Julia Bodensteiner of the European Southern Observatory in Garching, Germany, who was not involved in the new study. That second star in each system spins very fast, which makes them difficult to see in the spectra.

      What’s more, the lines in the spectrum of a star orbiting something will shift back and forth, El-Badry says. If one assumes the spectrum shows just one average, slow-spinning star in an orbit — which is what appeared to be happening in these systems at first glance — that assumption then leads to the erroneous conclusion that the star is orbiting an invisible black hole.

      Instead, the Unicorn and Giraffe each hold two stars, caught in a never-before-seen stage of stellar evolution, the researchers found after reanalyzing the data. Both systems contain an older red giant star with a puffy atmosphere and a “subgiant,” a star on its way to that late-life stage. The subgiants are near enough to their companion red giants that they are gravitationally stealing material from them. As these subgiants accumulate more mass, they spin faster, El-Badry says, which is what made them undetectable initially.

      “Everyone was looking for really interesting black holes, but what they found is really interesting binaries,” Bodensteiner says.

      These are not the only systems to trick astronomers recently. What was thought to be the nearest black hole to Earth also turned out to be pair of stars in a rarely seen stage of evolution (SN: 3/11/22).

      “Of course, it’s disappointing that what we thought were black holes were actually not, but it’s part of the process,” Jayasinghe says. He and his colleagues are still looking for black holes, he says, but with a greater awareness of how pairs of interacting stars might trick them. More

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      When the Magellanic Clouds cozy up to each other, stars are born

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      Like two great songwriters working side by side and inspiring each other to create their best work, the Magellanic Clouds spawn new stars every time the two galaxies meet.

      Visible to the naked eye but best seen from the Southern Hemisphere, the Large and Small Magellanic Clouds are by far the most luminous of the many galaxies orbiting the Milky Way. New observations reveal that on multiple occasions the two bright galaxies have minted a rash of stars simultaneously, researchers report March 25 in Monthly Notices of the Royal Astronomical Society: Letters.

      Astronomer Pol Massana at the University of Surrey in England and his colleagues examined the Small Magellanic Cloud. Five peaks in the galaxy’s star formation rate — at 3 billion, 2 billion, 1.1 billion and 450 million years ago and at present — match similarly timed peaks in the Large Magellanic Cloud. That’s a sign that one galaxy triggers star formation in the other whenever the two dance close together.

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      “This is the most detailed star formation history that we’ve ever had of the [Magellanic] Clouds,” says Paul Zivick, an astronomer at Texas A&M University in College Station who was not involved in the new work. “It’s painting a very compelling picture that these two have had a very intense set of interactions over the last two to three gigayears.”

      Even as the two galaxies orbit the Milky Way at 160,000 and 200,000 light-years from Earth, they also orbit each other (SN: 1/9/20). Their orbit is elliptical, which means they periodically pass near each other. Just as tides from the moon’s gravity stir the seas, tides from one galaxy’s gravity slosh around the other’s gas, inducing star birth, says study coauthor Gurtina Besla, an astrophysicist at the University of Arizona in Tucson.

      During the last encounter, which happened 100 million to 200 million years ago, the smaller galaxy probably smashed right through the larger, Besla says, which sparked the current outbreak of star birth. The last star formation peak in the Large Magellanic Cloud occurred only in its northern section, so she says that’s probably where the collision took place.

      Based on the star formation peaks, the period between Magellanic encounters has decreased from a billion to half a billion years. Besla attributes this to a process known as dynamical friction. As the Small Magellanic Cloud orbits its mate, it passes through the larger galaxy’s dark halo, attracting a wake of dark matter behind itself. The gravitational pull of this dark matter wake slows the smaller galaxy, shrinking its orbit and reducing how much time it takes to revolve around the Large Magellanic Cloud.

      The future for the two galaxies may not be so starry, however. They recently came the closest they’ve ever been to the Milky Way, and its tides, Besla says, have probably yanked the pair apart. If so, the Magellanic Clouds, now separated by 75,000 light-years, may never approach each other again, putting an end to their most productive episodes of star making, just as musicians sometimes flounder after leaving bandmates to embark on solo careers. More

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      Here’s the best timeline yet for the Milky Way’s big events

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      A new analysis of nearly a quarter million stars puts firm ages on the most momentous pages from our galaxy’s life story.

      Far grander than most of its neighbors, the Milky Way arose long ago, as lesser galaxies smashed together. Its thick disk — a pancake-shaped population of old stars — originated remarkably soon after the Big Bang and well before most of the stellar halo that envelops the galaxy’s disk, astronomers report March 23 in Nature.

      “We are now able to provide a very clear timeline of what happened in the earliest time of our Milky Way,” says astronomer Maosheng Xiang.

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      He and Hans-Walter Rix, both at the Max Planck Institute for Astronomy in Heidelberg, Germany, studied almost 250,000 subgiants — stars that are growing larger and cooler after using up the hydrogen fuel at their centers. The temperatures and luminosities of these stars reveal their ages, letting the researchers track how different epochs in galactic history spawned stars with different chemical compositions and orbits around the Milky Way’s center.

      “There’s just an incredible amount of information here,” says Rosemary Wyse, an astrophysicist at Johns Hopkins University who was not involved with the study. “We really want to understand how our galaxy came to be the way it is,” she says. “When were the chemical elements of which we are made created?”

      Xiang and Rix discovered that the Milky Way’s thick disk got its start about 13 billion years ago. That’s just 800 million years after the universe’s birth. The thick disk, which measures 6,000 light-years from top to bottom in the sun’s vicinity, kept forming stars for a long time, until about 8 billion years ago.

      During this period, the thick disk’s iron content shot up 30-fold as exploding stars enriched its star-forming gas, the team found. At the dawn of the thick disk era, a newborn star had only a tenth as much iron, relative to hydrogen, as the sun; by the end, 5 billion years later, a thick disk star was three times richer in iron than the sun.

      Xiang and Rix also found a tight relation between a thick disk star’s age and iron content. This means gas was thoroughly mixed throughout the thick disk: As time went on, newborn stars inherited steadily higher amounts of iron, no matter whether the stars formed close to or far from the galactic center.

      But that’s not all that was happening. As other researchers reported in 2018, another galaxy once hit our own, giving the Milky Way most of the stars in its halo, which engulfs the disk (SN: 11/1/18). Halo stars have little iron.

      The new work revises the date of this great galactic encounter: “We found that the merger happened 11 billion years ago,” Xiang says, a billion years earlier than thought. As the intruder’s gas crashed into the Milky Way’s gas, it triggered the creation of so many new stars that our galaxy’s star formation rate reached a record high 11 billion years ago.

      The merger also splashed some thick disk stars up into the halo, which Xiang and Rix identified from the stars’ higher iron abundances. These “splash” stars, the researchers found, are at least 11 billion years old, confirming the date of the merger.

      The thick disk ran out of gas 8 billion years ago and stopped making stars. Fresh gas around the Milky Way then settled into a thinner disk, which has given birth to stars ever since — including the 4.6-billion-year-old sun and most of its stellar neighbors. The thin disk is about 2,000 light-years thick in our part of the galaxy.

      “The Milky Way has been quite quiet for the last 8 billion years,” Xiang says, experiencing no further encounters with big galaxies. That makes it different from most of its peers.

      If the thick disk really existed 13 billion years ago, Xiang says, then the new James Webb Space Telescope (SN: 1/24/22) may discern similar disks in galaxies 13 billion light-years from Earth — portraits of the Milky Way as a young galaxy. More

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      Levitating plastic beads mimic the physics of spinning asteroids

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      Some asteroids can barely hold it together.

      Rather than solid lumps of rock, ‘rubble pile’ asteroids are loose collections of material, which can split apart as they rotate (SN: 3/16/20). To understand the inner workings of such asteroids, one team of scientists turned to levitating plastic beads. The beads clump together, forming collections that can spin and break up, physicist Melody Lim of the University of Chicago reported March 15 at a meeting of the American Physical Society in Chicago.

      It’s an elegant dance that mimics the physics of asteroid formation, which happens too slowly to observe in real-life space rocks. “These ‘tabletop asteroids’ compress phenomena that take place over kilometers [and] over hundreds of thousands of years to just centimeters and seconds in the lab,” Lim said. The results are also reported in a paper accepted in Physical Review X.

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      Lim and colleagues used sound waves to levitate the plastic beads, which arranged themselves into two-dimensional clumps. Acoustic forces attract the beads to one another, mimicking the gravitational attraction between bits of debris in space. Separate clumps then coalesced similarly to how asteroids are thought to glom onto one another to grow.

      [embedded content]
      Levitated by sound waves, plastic beads, which are about 150 micrometers across, clump together into a loosely bound 2-D conglomeration (shown at 1/50th the original speed). When spun too fast, one such structure deforms then splits apart (shown at 1/70th the original speed).

      When the experimenters gave the structures a spin using the sound waves, the clumps changed shape above a certain speed, becoming elongated. That could help scientists understand why ‘rubble pile’ asteroids, can have odd structures, such as the ‘spinning tops’ formed by asteroids Bennu and Ryugu (SN: 12/18/18).

      Eventually, the fast-spinning clumps broke apart. This observation could help explain why asteroids are typically seen to spin up to a certain rate, but not beyond: Speed demons get split up. More

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      NASA’s exoplanet count surges past 5,000

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      It’s official: The number of planets known beyond our solar system has just passed 5,000.

      The exoplanet census surpassed this milestone with a recent batch of 60 confirmed exoplanets. These additional worlds were found in data from NASA’s now-defunct K2 mission, the “second life” of the prolific Kepler space telescope, and confirmed with new observations, researchers report March 4 at arXiv.org.

      As of March 21, these finds put NASA’s official tally of exoplanets at 5,005.

      It’s been 30 years since scientists discovered the first planets orbiting another star — an unlikely pair of small worlds huddled around a pulsar (SN: 1/11/92). Today, exoplanets are so common that astronomers expect most stars host at least one (SN: 1/11/12), says astronomer Aurora Kesseli of Caltech.

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      “One of the most exciting things that I think has happened in the last 30 years is that we’ve really started to be able to fill out the diversity of exoplanets,” Kesseli says

      Some look like Jupiter, some look — perhaps — like Earth and some look like nothing familiar. The 5,005 confirmed exoplanets include nearly 1,500 giant gassy planets, roughly 200 that are small and rocky and almost 1,600 “super-Earths,” which are larger than our solar system’s rocky planets and smaller than Neptune (SN: 8/11/15).

      Astronomers can’t say much about those worlds beyond diameters, masses and densities. But several projects, like the James Webb Space Telescope, are working on that, Kesseli says (SN: 1/24/22). “Not only are we going to find tons and tons more exoplanets, but we’re also going to start to be able to actually characterize the planets,” she says.

      And the search is far from over. NASA’s newest exoplanet hunter, the TESS mission, has confirmed more than 200 planets, with thousands more yet to verify, Kesseli says (SN: 12/2/21). Ongoing searches from ground-based telescopes keep adding to the count as well.

      “There’s tons of exoplanets out there,” Kesseli says, “and even more waiting to be discovered.” More

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      Diamonds may stud Mercury’s crust

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      A treasure trove of diamonds may be sown into Mercury’s cratered crust.

      Billions of years of meteorite impacts may have flash-baked much of Mercury’s surface into the glittery gemstones, planetary scientist Kevin Cannon reported March 10 at the Lunar and Planetary Science Conference in The Woodlands, Texas. His computer simulations predict that such impacts may have transformed about one-third of the little planet’s crust into a diamond stockpile many times that of Earth’s.

      Diamonds are forged under immense pressures and temperatures. On Earth, the gemstones crystallize deep underground — at least 150 kilometers down — then ride to the surface during volcanic eruptions (SN: 9/14/20). But studies of meteorites suggest diamonds can also form during impact.

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      “When those [impacts] happen, they create very high pressures and temperatures that can transform carbon into diamond,” says Cannon, of the Colorado School of Mines in Golden.

      With impact-born diamonds on his mind, Cannon turned to the closest planet to the sun. Surveys of the planet’s surface and experiments with molten rock suggest that the planet’s crust may retain fragments of an old shell of graphite — a mineral made from carbon (SN: 3/7/16). “What we think happened is that when [Mercury] first formed, it had a magma ocean, and that graphite crystallized out of that magma,” Cannon says.

      Then, the bombardment. Mercury’s surface today is heavily cratered, evidence of an impact-rich history. Much of the purported graphite crust would have been battered and transformed into diamond, Cannon hypothesized.

      Curious how pervasive this diamond forging could have been, Cannon used computers to simulate 4.5 billion years of impacts on a graphite crust. The findings show that if Mercury had possessed a skin of graphite 300 meters thick, the battering would have generated 16 quadrillion tons of diamonds — about 16 times Earth’s estimated reserves.

      “There’s no reason to doubt that diamonds could be produced in this way,” says Simone Marchi, a planetary scientist at the Southwest Research Institute in Boulder, Colo., who was not involved with the research. But how many might have survived, that’s another story, he says. Some of the gemstones would probably have been destroyed by later impacts.

      Cannon agrees that subsequent impacts would probably obliterate some diamonds. But the losses would have been “very limited,” he says, as the ultimate melting point of diamond exceeds 4000° Celsius. Future simulations will incorporate remelting from impacts, he says, to refine the potential size of Mercury’s present day diamond reserves.

      An opportunity to scout for diamonds on Mercury may come in 2025, when the BepiColombo mission reaches the planet. Diamonds reflect a distinct signature of infrared light, Cannon says. “And potentially, this could be detected.” More

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      Some of the sun’s iconic coronal loops may be illusions

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      Coronal loops, well-defined hot strands of plasma that arch out into the sun’s atmosphere, are iconic to the sun’s imagery. But many of the supposed coronal loops we see might not be there at all.    

      Some coronal loops might be an illusion created by “wrinkles” of greater density in a curtain of plasma dubbed the coronal veil, researchers propose March 2 in Astrophysical Journal. If true, the finding, sparked by unexpected plasma structures seen in computer simulations of the sun’s atmosphere, may change how scientists go about measuring some properties of our star.

      “It’s kind of inspiring to see these detailed structures,” says Markus Aschwanden, an astrophysicist at Lockheed Martin’s Solar & Astrophysics Lab in Palo Alto, Calif., who was not involved in the study. “They are so different than what we anticipated.”

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      Scientists have begun to develop a better understanding of the sun’s complex atmosphere, or corona, only in the last few years (SN: 12/19/17). Coronal loops have been used to measure many properties of the corona, including temperature and density, and they may be key to figuring out why the sun’s atmosphere is so much hotter than its surface (SN: 8/20/17). But astronomers have long wondered just how the loops appear to be so orderly when they originate in the sun’s turbulent surface (SN: 8/17/17).     

      So solar physicist Anna Malanushenko and her colleagues attempted to isolate individual coronal loops in 3-D computer simulations originally developed to simulate the life cycle of a solar flare. The team expected to see neatly oriented strands of plasma, because coronal loops appear to align themselves to the sun’s magnetic field, like metal shavings around a bar magnet.

      Instead, the plasma appeared as a curtainlike structure winding out from the sun’s surface that folded in on itself like a wrinkled sheet. In the simulation, many of the supposed coronal loops turned out to not be real objects. While there were structures along the magnetic fields, they were neither thin nor compact as expected. They more closely resembled clouds of smoke. As the team changed the point of view from which they looked at these wrinkles in the veil in the simulation, their shape and orientation changed. And from certain viewing angles, the wrinkles resembled coronal loops.

      The observations were mind-blowing, says Malanushenko, of the National Center for Atmospheric Research in Boulder, Colo. “The traditional thought was that if we see this arching coronal loop that there is a garden hose–like strand of plasma.” The structure in the simulation was much more complex and displayed complicated boundaries and a raggedy structure.

      Still, not all coronal loops are necessarily illusions within a coronal veil. “We don’t know which ones are real and which ones are not,” Malanushenko says. “And we absolutely need to be able to tell to study the solar atmosphere.”

      It’s also not clear how the purported coronal veil might impact previous analyses of the solar atmosphere. “On one hand, this is depressing,” Malanushenko says of the way the new findings cast doubt on previous understandings. On the other hand, she finds the uncertainty exciting. Astronomers will need to develop a way to observe the veil and confirm its existence. “Whenever we develop new methods, we open the door for new knowledge.” More