Philippa Kaur

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    in Space & Astronomy

    A runaway black hole has been spotted fleeing a distant galaxy

    A streak of light stretching away from a remote galaxy might be the first sure sign of a gargantuan black hole on the run, a new study reports. The putative black hole, fleeing its host galaxy, appears to be leaving a trail of newborn stars and shocked gas in its wake. If confirmed, the intergalactic escape could help astronomers learn more about what happens to black holes when galaxies collide.

    “It’s a very cool, serendipitous discovery,” says astronomer Charlotte Angus of the University of Copenhagen, who was not involved in the new work. “The possibility that this might be due to a supermassive black hole that’s been ejected from its galaxy is very exciting. These events have been predicted by theory, but up until now, there’s been little evidence for them.”

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    While looking for colliding dwarf galaxies with the Hubble Space Telescope, astronomer Pieter van Dokkum and colleagues spotted something peculiar: a long, straight line that seemed to extend away from a distant galaxy, growing narrower and brighter as it went (SN: 5/18/22).

    “Whatever it is, we haven’t seen it before,” says van Dokkum, of Yale University. “Most astronomical objects are shaped like a spiral or a blob. There are not many objects that are just a line in the sky.” When astronomers do see lines, they’re usually from something moving, like a satellite crossing the telescope’s field of view (SN: 3/3/23).

    To figure out what it was, van Dokkum and colleagues took follow-up observations with the Keck Observatory in Hawaii. Those observations showed that the streak was associated with a galaxy whose light took about 8 billion years — more than half the age of the universe — to get to Earth, the team reports in a paper submitted February 9 to arXiv.org. The distance measurement let the team calculate the length of the line: roughly 200,000 light-years.

    That certainly ruled out a satellite.

    “We considered a lot of explanations, and the one that fit the best is what we’re witnessing is a massive object, like a black hole, moving very rapidly away from the galaxy,” van Dokkum says.

    The runaway black hole showed up as a straight line in a Hubble image (shown). The origin galaxy is at the top right of the streak. The galaxy is so far away that the line stretches for 200,000 light-years.P. van Dokkum et al/arXiv.org 2023

    Black holes on their own are invisible. But “if a black hole leaves a galaxy, it doesn’t leave by itself,” van Dokkum says. Some of the stars and gas that were gravitationally bound to the black hole leave with it. That gas will emit strong radiation that telescopes can detect. The black hole’s path through the gas and dust in the galaxy’s outer regions can compress some of that gas into new stars, too, which would also be visible (SN: 7/12/18).

    Another possibility is that the line is a jet of radiation launched by the galaxy’s central supermassive black hole. But that scenario would probably lead to a beam that is narrow when it is close to the galaxy and broadens as it gets farther away. This streak does the opposite.

    If it’s a black hole, it could have been ejected from the galaxy’s center by interacting with one or two other black holes nearby. Almost every galaxy has a supermassive black hole at its center. When galaxies merge, their central black holes also eventually merge (SN: 3/5/21). If the conditions are right, that merger can give the resulting black hole a “kick,” sending it flying away at high speed (SN: 4/25/22).

    Alternatively, the black hole could have been spat out of a smashup among three galaxies. When a third galaxy joins an ongoing merger, three supermassive black holes jockey for position. One black hole can be tossed out of the galactic smashup, while the other two take off more slowly in the other direction.

    That’s what van Dokkum thinks happened in this case. There are signs of a shorter, dimmer streak heading in the opposite direction from the bright, straight line.

    More observations of this system, perhaps with the James Webb Space Telescope, are needed to confirm that it really is an ejected supermassive black hole, Angus says. More theoretical calculations of what a runaway supermassive black hole should look like would help too.

    The finding motivates Angus to search through archived data for more potential black hole streaks. “I wonder if there are more of these features out there, sitting in someone’s data that might have just been missed,” she says.

    Van Dokkum does too. “Now that we know what to look for, these very thin streaks, it makes sense to go back to Hubble data. We have 25 years of Hubble images that have not been searched with this purpose,” he says. “If there are more to be found, I think we can do it.” More

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    in Humans

    Don't Miss: 65, a sci-fi dinosaur thriller by writers of A Quiet Place

    Patti Perret/Sony pictures
    Watch
    65 sees astronaut Mills (Adam Driver, pictured above) and a crew crash on an unknown planet – with dinosaurs. The sci-fi thriller, by Scott Beck and Bryan Woods (writers of A Quiet Place), is showing in cinemas from 10 March.

    Read
    The Biomimicry Revolution points us towards sustainable ways of living on Earth. Henry Dicks, an environmental philosopher, surveys our use of nature’s strategies to improve our surroundings. On sale from 14 March.
    Aflo Co Ltd/Alamy
    Visit
    The Use of Algorithms in Society is complex, says Cass Sunstein (pictured above), policy adviser and co-author of the bestseller … More

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    in Humans

    Relics illuminate the wreck of HMS Gloucester, a 17th-century warship

    A 3D representation of the wreck site is shown in this photogrammetry image from the Maritime Archaeology Trust.Norfolk Historic Shipwrecks Ltd
    THIS intriguing selection of images documents a catastrophic shipwreck that, after more than 300 years, has had some of its relics brought to the surface. They will be showcased in a new exhibition, The Last Voyage of the Gloucester, by the University of East Anglia and Norwich Castle Museum and Art Gallery, both in the UK.
    1682 painting of the wreck by Johan Danckerts.Royal Museums Greenwich/Wikimedia Commons
    In 1682, the warship HMS Gloucester set sail for Edinburgh carrying the future King James II of England and Ireland, who was also King James VII of Scotland. Not long into its journey, the ship struck a sandbank off the Norfolk coast and sank. James survived, but some 250 people on board died.Advertisment

    It wasn’t until 2007 that the miraculously well-preserved shipwreck was discovered by brothers Julian and Lincoln Barnwell, who had spent years scuba diving in search of the vessel. However, the pair were unable to reveal their find until last year so it could be protected.
    The ship’s lifting tools on the seabed
    A 3D representation of the wreck site is shown in the main picture in a photogrammetry image from the Maritime Archaeology Trust.

    Pictured above: a pair of glasses in their case; and below two salt-glazed jugs, known as Bellarmine bottles; and a “Sun in Splendour” bottle. All were found at the site.
    Two salt-glazed jugs, known as Bellarmine bottles, left; and a “Sun in Splendour” rightNorfolk Historic Shipwrecks
    Pictured below the 65-kilogram bronze bell of HMS Gloucester.

    The exhibition is at Norwich Castle Museum and Art Gallery until 10 September.

    Topics:archaeology/ships More

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    in Humans

    Anaximander review: Did Anaximander create science, asks Carlo Rovelli

    Most of the ideas of Anaximander (second from right) have come to us through the writing of AristotleElla_Ca/shutterstock
    Anaximander and the Nature of ScienceCarlo Rovelli (translated by Marion Lignana Rosenberg)(Allen Lane)
    ASTRONOMY was conducted at Chinese government institutions for more than 20 centuries before Jesuit missionaries turned up and, somewhat bemused, pointed out that Earth is round. Why, after so much close observation and meticulous record-keeping, did 17th-century Chinese astronomers still think Earth was flat?
    Theoretical physicist Carlo Rovelli addresses this in Anaximander and the Nature of Science, … More

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    in Humans

    Creature review: Human nature is key to a sci-fi ballet

    Jeffrey Cirio as the Creature, in a still from Asif Kapadia’s film adaptation of the ballet Creature.Courtesy BFI Distribution and English National Ballet
    Creature
    Asif Kapadia
    On limited release in the UK and Ireland

    In an isolated research station, lost amid snow and ice, a highly disciplined team of would-be astronauts is putting an experimental animal through its paces. Will the Creature (deliberately left ambiguous so as not to spoil things) survive the tests thrown at it: the cold, the isolation, the asphyxia?
    This is a science-fiction ballet (adapted for film) loosely based on 19th-century dramatist Georg … More

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    in Humans

    Earliest signs of horse riding found in 5000-year-old human remains

    A grave in Malomirovo, Bulgaria, containing a human skeleton bearing evidence of horse ridingMichał Podsiadło
    The earliest evidence of horse riding has been found in 5000-year-old human skeletons from south-east Europe.
    The bones of nine men from graves in Bulgaria, Hungary and Romania show hallmarks of horse riding in the patterns of wear on their spines, legs and pelvises.
    The adoption of horse riding is seen as one of the key developments of history, as it helped people to herd livestock, promoted trade and migration, and eventually transformed warfare.Advertisment
    “Suddenly, people had the possibility to move five times as fast and carry 10 times more than they were able to transport before – that’s revolutionary,” says Martin Trautmann at the University of Helsinki in Finland.
    It has long been suspected that the first people to domesticate horses were the Yamnaya, livestock herders originating in the Eurasian steppe north of the Black Sea and Caucasus mountains. They went on to colonise most of Europe in what some archaeologists see as a murderous rampage.
    Traces of horse milk have been found in shards of their pots. Although this shows that people kept horses, they may have done so first for their milk and meat, so it is unclear when they might have begun riding the animals.
    Trautmann’s team analyzed the remains of 217 human skeletons that had previously been found in Bulgaria, Hungary, Romania and Serbia for signs of wear on their bones that could indicate horse riding. They dated from between 3000 and 7000 years ago. “Bones are living tissue and if you are doing certain activities throughout your life, the attached muscles and ligaments exert pressure on the bones,” says team member Volker Heyd, also at the University of Helsinki.
    Several features have previously been proposed as hallmarks of horse riding, as they are sometimes present in modern people who spend a lot of time on horseback. They include wear of the top and bottom surfaces of the spinal vertebrae, caused by the up-and-down motion experienced on a horse.

    Another potential sign is a thicker and rougher area where thigh muscles join to thigh bones, showing heavy use of the thighs, which could be from needing to grip the horse with the legs. “There’s additional bone growth to make the area where ligament meets bone bigger, so it disperses the force better,” says Trautmann.
    The team assessed all the skeletons for six such hallmarks. Five individuals showed the strongest evidence for horse riding, having five or more of the signs. Another four skeletons showed four of the signs. All nine were male, dating from 4500 to 5000 years ago.
    But William Taylor at the University of Colorado Boulder says other kinds of evidence of riding, such as remains of bridles, don’t show up in the archaeological record from this region until about 1000 years later. “It does zoom in on this region of the steppes as a homeland, but we are off by almost a millennium.”
    The patterns of wear on the bones aren’t conclusive proof of horse riding, as they could have been caused by other activities, such as riding in a cart pulled by cattle, he says. “We don’t have the kind of data I would like to see to let human skeletons track horse riding versus other activities.”

    Topics:archaeology/ancient humans More