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    Why losing Arecibo is a big deal for astronomy

    Edgard Rivera-Valentín first visited the Arecibo Observatory as a little kid.
    “I definitely remember this feeling of just being awestruck,” Rivera-Valentín says. “Looking at this gigantic telescope … getting to hear about all this neat work that was being done … it definitely leaves an impression.” Important science was happening right in the backyard of Rivera-Valentín’s hometown of Arecibo, Puerto Rico — and someday, Rivera-Valentín wanted to be a part of it.
    As an adult, Rivera-Valentín returned to the observatory to work as a planetary scientist, using Arecibo to map the shapes and motions of potentially dangerous near-Earth asteroids. Now at the Lunar and Planetary Institute in Houston, Rivera-Valentín continues to use Arecibo data to study planetary surfaces. So the recent news that the Arecibo Observatory would shut down was “heartbreaking.”
    In August and November, two cables supporting a 900-metric-ton platform of scientific instruments above Arecibo’s dish unexpectedly broke. After assessing the damage, the National Science Foundation, which funds Arecibo, announced that the telescope could not be safely repaired and would be torn down (SN: 11/19/20). But before the telescope could be dismantled, the entire instrument platform crashed down into the dish on December 1.
    [embedded content]
    After suffering damage in recent months, the Arecibo Observatory radio telescope in Puerto Rico collapsed on December 1. Cables that suspended a platform of scientific instruments above the dish snapped, causing the platform to fall into the dish.
    For Puerto Rico, losing Arecibo is like New York losing the Empire State Building, or San Francisco losing the Golden Gate Bridge, Rivera-Valentín says — but with the added tragedy that Arecibo was not just a cultural and historic icon, but a prolific research facility.
    “The loss of Arecibo is a big loss for the community,” says Tony Beasley, director of the National Radio Astronomy Observatory in Charlottesville, Va. “The life cycle of Arecibo was really quite remarkable, and it did some amazing science.”
    The observatory’s radar maps of the moon and Mars, for example, helped NASA pick landing sites for the Apollo (SN: 5/1/65) and Viking missions (SN: 7/17/76). And observations of the asteroid Bennu helped NASA plan its OSIRIS-REx mission to snag a sample from the space rock (SN: 10/21/20). Arecibo views of Saturn’s moon Titan have revealed hydrocarbon lakes on its surface (SN: 10/1/03).
    Beyond the solar system, Arecibo has observed mysterious flashes of radio waves from deep space, called fast radio bursts (SN: 2/7/20), and the distribution of galaxies in the universe. Arecibo has also been used for decades in the search for extraterrestrial intelligence (SN: 11/7/92), and it beamed the first radio message to aliens into space in 1974 (SN: 11/23/74).
    In the wake of Arecibo’s collapse, the radio astronomy community is “going to have to look at what was going on at Arecibo and figure out how to replace as best we can some of those capabilities with other instruments,” Beasley says.
    In its 57-year lifetime, the huge radio telescope at the Arecibo Observatory in Puerto Rico (shown) made important discoveries in planetary science and astronomy.University of Central Florida
    But many of Arecibo’s capabilities can’t be easily replaced.
    “Arecibo was unique in several ways,” says Donald Campbell, an astronomer at Cornell University and a former director of the observatory. For starters, Arecibo was enormous. At 305 meters across — covering some 20 acres — Arecibo was the world’s largest radio dish from the time it was built in 1963 (SN: 11/23/63) until 2016, when China completed its Five-Hundred-Meter Aperture Spherical Telescope, or FAST. With such a huge dish to collect radio waves, Arecibo could see very faint objects and phenomena.
    That incredible sensitivity made Arecibo particularly good at detecting hard-to-spot objects such as rapidly spinning neutron stars called pulsars (SN: 1/3/20). As a pulsar rotates, it sweeps a beam of radio waves around in space like a lighthouse, which appears to Earth as a radio beacon flickering on and off.
    “Arecibo was the king” of spotting the fickle light of pulsars, Beasley says. “There’s not going to be a simple solution to regenerating that level of collecting area.” The next biggest radio dish in the United States is the 100-meter-wide Green Bank Telescope in West Virginia. Smaller telescopes may require several hours of observing a target to collect enough radio waves for analysis, whereas Arecibo took only minutes.
    Besides its mammoth size, Arecibo could also transmit radio waves. “Most radio astronomy telescopes do not have transmitters,” Campbell says. “They’re just receiving radio waves from space.” Radar transmitters allowed Arecibo to bounce radio waves off of gases in the atmosphere (SN: 1/31/70), or the surfaces of asteroids and planets. The reflected signals that came back contained information about the target such as size, shape and motion.

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    “The high-powered transmitters allowed what was the original primary purpose of the telescope — the study of the Earth’s ionosphere,” Campbell says. The U.S. military, which funded the construction of Arecibo, wanted to better understand Earth’s atmosphere to help develop missile defenses (SN: 2/10/68). But Arecibo’s radar transmitters “were also used to study solar system bodies — the planets, the moons, including our own moon,” Campbell says. “More recently, the emphasis has been on studying near-Earth asteroids” that could be on a collision course with Earth.
    Other big radio dishes, such as China’s FAST or the Green Bank Telescope, are not outfitted with radar transmitters. NASA’s Goldstone Deep Space Communications Complex in the Mojave Desert has a 70-meter dish with radar capabilities. But Goldstone “is used both as a military installation and also as part of the Deep Space Network that talks to spacecraft, so it doesn’t have a lot of time,” Rivera-Valentín says. “And it’s not as sensitive as Arecibo,” so it can’t see as many asteroids.
    Even at the time of its demise, the Arecibo Observatory still had “a bright scientific future,” says Joan Schmelz, an astronomer at the Universities Space Research Association in Mountain View, Calif., and a former deputy director of the observatory. “It wasn’t just resting on its laurels.” For instance, Arecibo was a key facility for the ongoing NANOGrav project, which uses observations of pulsars to search for ripples in spacetime kicked up by supermassive black holes (SN: 9/24/15).
    Arecibo’s observing days may be over, but that doesn’t mean data from the telescope won’t make any more contributions to science, Schmelz says. Some of radio astronomy’s most exciting discoveries have emerged from the reanalysis of old telescope data (SN: 7/25/14). “People will be continuing to analyze Arecibo data for some time,” she says, “and we’ll hopefully be seeing new scientific results as those data get analyzed and published.” More

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    Stone Age humans chose to voyage to Japanese islands over the horizon

    By Donna Lu
    Archaeologists have built replica Stone Age rafts to attempt the crossing to the Ryukyu islands
    Yosuke Kaifu

    Stone Age humans crossed the sea from Taiwan to the Ryukyu islands of south-west Japan tens of thousands of years ago – and it looks like they did so deliberately, even though the islands are too far away to be reliably visible from Taiwan.
    Archaeological sites on several of the Ryukyu islands suggest humans had reached the islands by about 30,000 to 35,000 years ago. Yosuke Kaifu at the University of Tokyo and his colleagues suspect the ancient people did so by travelling north-east from Taiwan – a journey that involved ocean crossings of tens to hundreds of kilometres to hop from island to island. The researchers have even repeated some of these ocean crossings themselves using bamboo rafts of the kind that Stone Age humans might have built.
    But it hadn’t been clear whether the crossing occurred deliberately or by accident. The Kuroshio current, which flows from Luzon in the Philippines past Taiwan and Japan, is one of the strongest ocean currents in the world, and in some parts is 100 kilometres wide.

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    “The speed of the Kuroshio in the east of Taiwan is normally 1 to 2 metres per second,” says Kaifu.

    To find out if people could have arrived at the islands by drifting on this current, the researchers looked at existing data from 138 satellite-tracked buoys, released into the world’s oceans as part of the Global Drifter Program. The 138 buoys all drifted past Taiwan or Luzon between 1989 and 2017.
    Kaifu and his colleagues found that only four buoys travelled to within 20 kilometres of any of the Ryukyu islands. In all four cases this occurred as a result of adverse weather conditions, including a typhoon.
    The finding suggests that the Kuroshio current directs drifters away from, rather than towards, the Ryukyu islands. Because the flow of the current is thought to have stayed the same for the past 100,000 years, it seems likely that Stone Age people reached the Ryukyu islands through deliberate voyaging rather than accidental drifting.
    “Now we can tell with confidence that Palaeolithic people set sail deliberately even to a remote invisible island,” says Kaifu.

    “Most people probably think that Palaeolithic people were just primitive and conservative, but I now see something different from that general image,” he says.
    Journal reference: Scientific Reports, DOI: 10.1038/s41598-020-76831-7
    More on these topics: More

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    Christmas gift ideas: The 13 best science and technology books of 2020

    From The End of Everything by Katie Mack and How to Argue with a Racist by Adam Rutherford to Martha Wells’s Murderbot sc-ifi series, New Scientist’s 2020 gift guide has a book for everyone

    Humans 2 December 2020
    By New Scientist

    Getty Images/Westend61

    The End of Everything (Astrophysically Speaking)
    by Katie Mack
    For a bit of seasonal giving, why not look to the end of the universe? Thankfully, The End of Everything (Scribner) by Katie Mack is no apocalyptic vision but an engrossing and often funny tour of all the ways our cosmos might come to a close. Mack’s enjoyment of physics stands out – and is contagious. She describes primordial black holes as “awfully cute in a terrifying theoretical kind of way”, antimatter as “matter’s annihilation-happy evil twin” and the universe as “frickin’ weird”. All true, and Mack’s explanations … More

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    Watch Dogs: Legion review – The perfect antidote to lockdown

    In Watch Dogs: Legion you can play as or team up with any of the characters of the game, and strolling around its digital version of London is a real treat, says Jacob Aron

    Humans 2 December 2020
    By Jacob Aron
    Key London landmarks like The Shard appear in Watch Dogs: Legion
    Ubisoft

    Watch Dogs: LegionUbisoftPC, PlayStation 4 and 5, Xbox One, Series X and S
    NEW SCIENTIST closed its offices on 13 March, a week or so before the UK went into national lockdown. Since then, I have spent most of this year in a small radius around my north London flat and have been into the city centre only a handful of times.
    As a native Londoner, it is strange to be so cut off from the city, which is why the opening moments of Watch … More

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    The Scandinavian secrets to keeping positive in a covid-19 winter

    Lockdown restrictions in winter might seem something to dread, but we can combat this by embracing the mindset of people used to long, dark winters, says health psychologist Kari Leibowitz

    Health 2 December 2020
    By Kari Leibowitz

    Rocio Montoya

    WHEN health psychologist Kari Leibowitz moved from the US to the Norwegian town of Tromsø, more than 300 kilometres north of the Arctic circle, her research became personal. Inspired by recent findings on the ways in which people’s attitudes influence their mental and physical health, she wondered whether this might be the secret to coping with the long, dark Nordic winter. Her research revealed that many Norwegians have a winter mindset that allows them to thrive in conditions she was dreading. Now back in the US at Stanford University, Leibowitz believes her findings hold lessons for us all, especially for people living in the northern hemisphere who, as the nights draw in, face the dual challenges of winter and a stressful pandemic.
    David Robson: What are “mindsets” and why are they so important?
    Kari Leibowitz: I think of mindsets as a framework that helps us simplify information and make sense of the world. And we’re really just at the beginning of unpacking the ways that they can shape our health and well-being.
    A lot of my research now is looking at how we can use mindsets in clinical practice. In one of the last studies that I did, we tested the effects of changing people’s mindsets – even without treatment. We brought our participants to the lab and we pricked them with histamine, triggering a minor allergic reaction that looks a bit like a mosquito bite. For some people, a doctor just examined their arm; for the others, the doctor examined their arm and said: “OK, from now on, the itch and irritation will feel better and your … More

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    December’s stunning Geminid meteor shower is born from a humble asteroid

    On Sunday night, December 13, countless meteors will shoot across the sky as space particles burn up in our atmosphere and meet a fiery end. Most meteor showers occur when Earth slams into debris left behind by a comet.
    But not this meteor shower, which is likely to be the most spectacular of the year. Known as the Geminid shower, it strikes every December and arises not from a flamboyant comet but from an ordinary asteroid — the first, but not the last, linked to a meteor shower.
    Although both comets and asteroids are small objects orbiting the sun, icy comets sprout beautiful tails when their ice vaporizes in the heat of the sun. In contrast, asteroids have earned the name “vermin of the skies” for streaking through and ruining photographs of celestial vistas by reflecting the sun’s light.
    So how can a mere asteroid outdo all of the glamorous comets and spawn a meteor shower that surpasses its rivals? “It remains a mystery,” says David Jewitt, an astronomer at UCLA. It’s akin to an ugly duckling’s offspring usurping the beautiful swan’s to win first place in a beauty contest.
    Astronomers still don’t know the secret to the asteroid’s success in creating a shower that at its peak normally produces more meteors per hour than any other shower of the year. Three years ago, however, the asteroid swung extra close to Earth and gave scientists their best chance to study the humble space rock. They now look forward to the launch of a spacecraft that will image the asteroid’s surface.

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    Cosmic connections
    Astronomers first linked a meteor shower to a comet in 1866. They connected the well-known Perseid meteors, visible to most of the world every August, with a comet named Swift-Tuttle that had passed Earth four years earlier. Astronomers later matched most major meteor showers with one comet or another.
    When a comet’s ice vaporizes in sunlight, dust grains also fly off the comet. These dust particles, called meteoroids, sprinkle along the comet’s orbit like a dandelion gone to seed. If Earth plows into this long dust stream, we see a fiery shower as the particles hit our atmosphere. The typical meteoroid is no larger than a grain of sand, but it travels so fast that it energizes electrons both in its own atoms as it disintegrates and in atmospheric atoms and molecules. As these electrons lose energy, they emit the streak of light — the meteor — that looks as though a star has fallen from the sky.
    Still, as comet after comet was linked to different meteor showers, the Geminids remained apart; no one knew their source.
    The Geminid meteors stood out in other ways, too. Unlike the Perseid meteors, which people have been observing for nearly 2,000 years, the Geminids are relatively new. First reports of their existence came from England and the United States in 1862. The shower in those days was weak, producing at most only one or two dozen meteors an hour. During the 20th century, however, the shower strengthened. Nowadays, at the shower’s peak, a single observer under a dark sky can see more than 100 meteors an hour. That’s better than most Perseid performances.
    On top of that, the Geminid meteoroid stream, the ribbon of dust that traces the asteroid’s orbit around the sun, is newer than many other streams. Over time, streams spread out, but this one is so narrow it must have formed less than 2,000 years ago and maybe only a few hundred years ago. And based on how little the meteoroids slow down when they hit the air, astronomers deduced that Geminid meteoroids are fairly dense, about three times as dense as water and twice as dense as the Perseid meteoroids.

    In 1983, astronomers finally found the Geminids’ parent. Jewitt, then a graduate student at Caltech, remembers walking home one January evening when he happened to see a rocket lift off from a military base. “I assumed it was an ICBM or something that the Air Force was launching to test,” he says. Instead, it was a heat-seeking spacecraft named the Infrared Astronomical Satellite.
    In October of that year, the satellite discovered a small asteroid. To Harvard astronomer Fred Whipple, best known for his “dirty snowball” model of comets (SN: 3/14/92, p. 170), that small object stood out. It followed the same path around the sun as the particles in the Geminid meteoroid stream. Half a century earlier, Whipple himself had determined the orbit of the meteoroids by photographing the paths of the meteors against the sky. The newfound asteroid, Whipple declared, must be their long-sought source. The find also explained why the meteoroids were so dense: They come from a space rock rather than an icy comet.
    The asteroid revolves around the sun every 1.43 years and comes very close to the sun, cutting well inside the orbit of Mercury, the innermost planet. Astronomers therefore christened the asteroid Phaethon, a son of Helios the sun god in Greek mythology. At its farthest, Phaethon ventures beyond the orbit of Mars and reaches the asteroid belt, home of the largest space rocks, between the paths of Mars and Jupiter.
    For a quarter century after Phaethon’s discovery, though, no one saw it shedding any dust particles or pebbles that could account for the many meteors that make up December’s show. Because of the sun’s glare, astronomers couldn’t observe Phaethon when it was closest to the sun. Observing during a close pass might be especially interesting because calculations indicated that the intense sunlight caused Phaethon’s surface temperature to soar to roughly 1,000 kelvins (1,340° Fahrenheit), hotter than any planet in the solar system. The torrid temperature might cause the asteroid to shoot particles into space.
    A lucky break came about because Jewitt married an astrophysicist who studies the sun. “Really, the key was talking to my wife about this,” he says. Jing Li, also at UCLA, and Jewitt realized that a solar spacecraft might be able to pick up details about the asteroid when it’s nearest the sun and thus offer clues to why the space rock is such a fertile meteor-maker.
    Sure enough, in 2009 and again in 2012, images taken by a NASA solar spacecraft named STEREO A caught Phaethon brightening when near the sun, which suggested the asteroid was throwing off dust particles. Then, in 2013, Jewitt and Li noticed a short dust tail in that data. The tail lasted only two days. “It’s really, really faint in basically the world’s crappiest data,” Jewitt says. The bright background sky makes the tail hard to see.
    The researchers attribute Phaethon’s dust production to the extreme heat, which breaks rocks on the asteroid’s surface and sends particles aloft. Phaethon has so little gravity that those particles can escape into space. Additional dust may result from desiccation, Jewitt says: In the presence of such heat, hydrated minerals on the asteroid may dry out and crack, the way empty lake beds do on Earth, releasing more particles.
    As seen from California’s Mojave Desert in 2009, a Geminid meteor streaks past Orion’s Belt. Walter Pacholka, Astropics/Science Source
    Phaethon’s fast spin causes further stress. The asteroid makes a full turn every three hours and 36 minutes. Such rapid rotation is typical of small asteroids, and it means the surface freezes and then fries over a short period of time. The spin also creates a centrifugal force that might help lift particles into space.
    Yet these findings don’t solve the mystery of how a modest asteroid produces such a stunning meteor shower, Jewitt says. For one thing, as he and colleagues noted in 2013 in the Astrophysical Journal Letters, the particles in Phaethon’s temporary tail are much too small.
    Most of the Geminid meteors we see come from particles roughly a millimeter across. But the particles in the tail are even tinier, spanning only about one one-thousandth of a millimeter. Jewitt and Li deduced the small size because sunlight exerts radiation pressure, which is weak, that pushes the tail straight back away from the sun; if the particles were larger, they would resist the weak pressure and the tail would be curved.
    Plus, Phaethon’s close passages to the sun don’t eject nearly enough particles to populate the Geminid stream. This suggests that some catastrophe hit the asteroid in the recent past and made so many meteoroids that they continue to delight meteor observers today.
    In 2014, astronomer Richard Arendt of the University of Maryland, Baltimore County reported the first direct sighting of the Geminid meteoroid stream itself. He had reanalyzed old data from a spacecraft whose chief mission had nothing to do with the solar system: the Cosmic Background Explorer, which NASA had launched a quarter century earlier to study the Big Bang’s afterglow and probe the universe’s birth.
    “They didn’t really have the tools to look at the data in the right way back then,” Arendt says. With modern computers, he made movies of the data and glimpsed glowing strands of dust threading the solar system that emit infrared light as the sun heats them. He used this approach to view the never-before-seen dust trail along the orbit of Halley’s comet, as well as Phaethon’s dust trail: the Geminid meteoroid stream, which looked like a narrow filament along Phaethon’s orbit. Arendt published his work in the Astronomical Journal.
    More recently, NASA’s Parker Solar Probe also detected the stream (SN: 1/18/20, p. 6). “This is the first time it’s been seen in visible light,” says Karl Battams, an astrophysicist at the U.S. Naval Research Laboratory in Washington, D.C. Sunlight hits the dust, reflecting the light to the probe. The observations put the stream’s mass at roughly 1 percent that of Phaethon itself. This is much more material than the asteroid produces when closest to the sun, which Battams says again favors the idea that the bulk of the Geminid meteoroid stream owes its existence to some past catastrophe.
    Phaethon visits Earth
    In December 2017, the asteroid helped astronomers by flying only 10 million kilometers from Earth, the closest the rock will come until 2093. “This was a great opportunity to look at Phaethon,” says Patrick Taylor, an astronomer then at Arecibo Observatory in Puerto Rico.
    Hurricane Maria had devastated the island and damaged the radio telescope just three months earlier, yet the observations succeeded. “That was the result of a tremendous amount of effort by the observatory staff, the community and the local government,” Taylor says. The telescope was repaired, and commercial power was restored to the observatory by clearing roads and replacing downed poles and cables to the site. “Everyone was aware how important this observation was going to be,” he says.
    Over a period of five days, his team bounced radar signals off the asteroid, watching different features come into view as the rock rotated. As published in 2019 in Planetary and Space Science, the observations indicate that Phaethon’s equatorial diameter is about 6.25 kilometers, which means the asteroid is a bit more than half the size of the one that hit Earth and did in the dinosaurs (SN: 2/15/20, p. 7). The images show what may be craters, one more than a kilometer across, on Phaethon’s surface. There’s also a possible boulder 300 meters wide.
    The radar images suggest Phaethon isn’t perfectly round. Instead, it may resemble a spinning top, like Bennu and Ryugu, two even smaller asteroids that spacecraft have recently visited. Both of those asteroids have equatorial diameters larger than their polar diameters. More than a thousand Bennus could fit inside Phaethon, but the two asteroids have similar shapes, Taylor notes. He thinks Phaethon may owe its shape to its rapid spin.

    Jewitt also tried to take advantage of Phaethon’s close visit. “It was a bit of a letdown,” he says, laughing. “We saw absolutely nothing at all.” Neither the Hubble Space Telescope nor the Very Large Telescope in Chile discerned any dust or rocks coming off the asteroid.
    But the future should hold much better views. In 2024, Japan will launch the DESTINY+ spacecraft, which will fly past Phaethon several years later. Japan has already sent spacecraft to two other small asteroids, and the new mission promises sharp images that should reveal Phaethon’s shape, structure, geologic features and dust trail. The spacecraft may even see the asteroid emit particles in real time, as NASA’s OSIRIS-REx mission did for Bennu (SN: 4/13/19, p. 10).
    The DESTINY+ spacecraft will search for signs of a recent catastrophe that could have excavated enough material to create the Geminid meteoroid stream. The most obvious possibility — an impact with another asteroid — is also the least likely, Jewitt says, because Phaethon is a small target and the impact would have had to occur less than 2,000 years ago. Nevertheless, if such an impact did happen, it surely carved a fresh scar, which a spacecraft might pick up.
    Perhaps some other catastrophe made the meteoroids. Maybe the asteroid was once a larger object that broke apart, because sunlight stressed it or it spun too fast. In fact, one or two other asteroids, smaller than Phaethon, follow similar paths around the sun and could be remnants of a super-Phaethon. After DESTINY+ zips by Phaethon, it may visit one of these other asteroids to investigate.
    There’s another question the spacecraft might address: The Geminids come from Phaethon, all right, but where did Phaethon come from? It wasn’t born where it is, because it crosses the paths of four planets. Within just a few tens of millions of years, it will either crash into one of them or else their gravity will hurl the rock into the sun or far away from it.
    Some astronomers have proposed that Phaethon is really a chunk kicked off of the large asteroid Pallas, a resident of the asteroid belt. “Could Phaethon be a piece of Pallas? Yes,” Jewitt says. “Is it likely to be a piece of Pallas? I’m not really sure about that.” The two asteroids resemble each other in composition, but there are also differences. Those distinctions may merely mean that strong sunlight has altered Phaethon’s surface. Or they may indicate the two asteroids have nothing to do with each other.
    Whatever the case, this month’s show should be especially good because moonlight won’t interfere. Any astronomers watching may make a wish on the falling stars for greater insight into how those meteors and their unlikely parent came to be. More

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    Astronomers spotted colliding neutron stars that may have formed a magnetar

    A surprisingly bright cosmic blast might have marked the birth of a magnetar. If so, it would be the first time that astronomers have witnessed the formation of this kind of rapidly spinning, extremely magnetized stellar corpse.
    That dazzling flash of light was made when two neutron stars collided and merged into one massive object, astronomers report in an upcoming issue of the Astrophysical Journal. Though the especially bright light could mean that a magnetar was produced, other explanations are possible, the researchers say.
    Astrophysicist Wen-fai Fong of Northwestern University in Evanston, Ill., and colleagues first spotted the site of the neutron star crash as a burst of gamma-ray light detected with NASA’s orbiting Neil Gehrels Swift Observatory on May 22. Follow-up observations in X-ray, visible and infrared wavelengths of light showed that the gamma rays were accompanied by a characteristic glow called a kilonova.
    Kilonovas are thought to form after two neutron stars, the ultradense cores of dead stars, collide and merge. The merger sprays neutron-rich material “not seen anywhere else in the universe” around the collision site, Fong says. That material quickly produces unstable heavy elements, and those elements soon decay, heating the neutron cloud and making it glow in optical and infrared light (SN: 10/23/19).
    [embedded content]
    A new study finds that two neutron stars collided and merged, producing an especially bright flash of light and possibly creating a kind of rapidly spinning, extremely magnetized stellar corpse called a magnetar (shown in this animation). 
    Astronomers think that kilonovas form every time a pair of neutron stars merge. But mergers produce other, brighter light as well, which can swamp the kilonova signal. As a result, astronomers have seen only one definitive kilonova before, in August 2017, though there are other potential candidates (SN: 10/16/17).
    The glow that Fong’s team saw, however, put the 2017 kilonova to shame. “It’s potentially the most luminous kilonova that we’ve ever seen,” she says. “It basically breaks our understanding of the luminosities and brightnesses that kilonovae are supposed to have.”
    The biggest difference in brightness was in infrared light, measured by the Hubble Space Telescope about 3 and 16 days after the gamma-ray burst. That light was 10 times as bright as infrared light seen in previous neutron star mergers.
    “That was the real eye-opening moment, and that’s when we scrambled to find an explanation,” Fong says. “We had to come up with an extra source [of energy] that was boosting that kilonova.”
    Her favorite explanation is that the crash produced a magnetar, which is a type of neutron star. Normally, when neutron stars merge, the mega-neutron star that they produce is too heavy to survive. Almost immediately, the star succumbs to intense gravitational forces and produces a black hole.
    But if the supermassive neutron star is spinning rapidly and is highly magnetically charged (in other words, is a magnetar), it could save itself from collapsing. Both the support of its own rotation and dumping energy, and thus some mass, into the surrounding neutron-rich cloud could keep the star from turning into a black hole, the researchers suggest. That extra energy in turn would make the cloud give off more light — the extra infrared glow that Hubble spotted.

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    But there are other possible explanations for the extra bright light, Fong says. If the colliding neutron stars produced a black hole, that black hole could have launched a jet of charged plasma moving at nearly the speed of light (SN: 2/22/19). The details of how the jet interacts with the neutron-rich material surrounding the collision site could also explain the extra kilonova glow, she says.
    If a magnetar was produced, “that could tell us something about the stability of neutron stars and how massive they can get,” Fong says. “We don’t know the maximum mass of neutron stars, but we do know that in most cases they would collapse into a black hole [after a merger]. If a neutron star did survive, it tells us about under what conditions a neutron star can exist.”
    Finding a baby magnetar would be exciting, says astrophysicist Om Sharan Salafia of Italy’s National Institute for Astrophysics in Merate, who was not involved in the new research. “A newborn highly magnetized, highly rotating neutron star that forms from the merger of two neutron stars has never been observed before,” he says.
    But he agrees that it’s too soon to rule out other explanations. What’s more, recent computer simulations suggest that it might be difficult to see a newborn magnetar even if it formed, he says. “I wouldn’t say this is settled.”
    Observing how the object’s light behaves over the next four months to six years, Fong and her colleagues have calculated, will prove whether or not a magnetar was born.
    Fong herself plans to keep following up on the mysterious object with existing and future observatories for a long time. “I’ll be tracking this till I’m old and grey, probably,” she says. “I’ll train my students to do it, and their students.” More

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    Tiny island survived tsunami that helped separate Britain and Europe

    By Michael Marshall
    By 8200 years ago (8200 calibrated years before the present), Doggerland existed as a small archipelago, which had drowned by 7000 years ago
    M. Muru

    The Atlantis of northern Europe sank under the seas slowly, rather than being obliterated by a tsunami. A little over 8000 years ago, a devastating tsunami swept across the North Sea, striking a small island that existed there at the time. But new evidence suggests the wave didn’t permanently swamp Dogger Island and its surrounding archipelago. People may have lived on the remaining land for centuries afterwards.
    Between 110,000 and 12,000 years ago, Earth was in the grip of a glacial period – sometimes rather misleadingly called the last ice age. Because so much water was locked up in ice at the poles, sea levels were many metres lower. This means land that is now underwater was exposed.
    This includes much of what is now the southern North Sea, between Britain and mainland Europe. As a result, Britain was connected to Europe by a fertile plain called Doggerland.

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    What happened to it? We know much of the polar ice melted, causing sea levels to rise around the world. By about 8200 years ago, Doggerland had gradually shrunk in size, leaving Dogger Island surrounded by a small archipelago (see image, above left). There is some evidence that this final piece of Doggerland had a dramatic end.

    About 8150 years ago, a submarine landslide occurred off the coast of Norway, dubbed the Storegga Slide. This created a tsunami in the North Sea that hit the surrounding coastlines – in many areas, the wave was many metres deep. Many researchers have argued that the Storegga tsunami helped cut Britain off from Europe.
    The issue is that so far, we have had no archaeological records of the tsunami’s impact on Doggerland. “We know essentially nothing about the actual impact on the areas which were patently most susceptible to be hit,” says Vince Gaffney at the University of Bradford in the UK.
    As part of a long-term project to map Doggerland, Gaffney’s team took sediment cores from the seabed off the coast of East Anglia, in the east of England. The cores contain traces of the Storegga tsunami, such as broken shells. It seems the tsunami slammed up a river valley, ripping trees from the sides – and leaving their DNA in the sediments for the team to find. But the water soon retreated and later sediments suggest the area was above water again.
    Gaffney’s team compiled existing data from around the North Sea. The researchers argue this suggests the Dogger archipelago survived for several more centuries. By 7000 years ago, it was underwater and had become what is now Dogger Bank: a submarine sand bank.

    Simply obtaining the sediment cores was “a major undertaking”, says Karen Wicks at the University of Reading in the UK.

    “It kind of confirms things we’d been thinking anyway,” says Sue Dawson at the University of Dundee in the UK.
    Simulations of the tsunami had suggested it couldn’t have swamped Doggerland, and in some places, such as northern Norway, the wave may have been fairly small. The crucial factor is the exact shape of the coastline and nearby seabed, which affects how high the water rises, says Dawson.
    Wicks has previously found evidence that the hunter-gatherer population in north-east Britain fell around the time of the tsunami. She argues that the tsunami was part of a “perfect storm” of environmental crises in the region, as it combined with a period of climate cooling 8200 years ago.
    However, almost nothing is known about the people living on Doggerland. Last year, Gaffney’s team recovered the first known artefacts: two small pieces of flint. As a result, it is unclear how long people continued living there as the area slipped beneath the sea.
    Journal reference: Antiquity, DOI: 10.15184/aqy.2020.49
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