Philippa Kaur

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    in Space & Astronomy

    The first black hole ever discovered is more massive than previously thought

    The first black hole ever discovered still has a few surprises in store.
    New observations of the black hole–star pair called Cygnus X-1 indicate that the black hole weighs about 21 times as much as the sun — nearly 1.5 times heavier than past estimates. The updated mass has astronomers rethinking how some black hole–forming stars evolve. For a star-sized, or stellar, black hole that massive to exist in the Milky Way, its parent star must have shed less mass through stellar winds than expected, researchers report online February 18 in Science.
    Knowing how much mass stars lose through stellar winds over their lifetimes is important for understanding how these stars enrich their surroundings with heavy elements. It’s also key to understanding the masses and compositions of those stars when they explode and leave behind black holes.
    The updated mass measurement of Cygnus X-1 is “a big change to an old favorite,” says Tana Joseph, an astronomer at the University of Amsterdam not involved in the work. Stephen Hawking famously bet physicist Kip Thorne that the Cygnus X-1 system, discovered in 1964, did not include a black hole — and conceded the wager in 1990, when scientists had broadly accepted that Cygnus X-1 contained the first known black hole in the universe (SN: 4/10/19).

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    Astronomers got a new look at Cygnus X-1 using the Very Long Baseline Array, or VLBA. This network of 10 radio dishes stretches across the United States, from Hawaii to the Virgin Islands, collectively forming a continent-sized radio dish. In 2016, the VLBA tracked radio-bright jets of material spewing out of Cygnus X-1’s black hole for six days (the time it took for the black hole and its companion star to orbit each other once). Those observations offered a clear view of how the black hole’s position in space shifted over the course of its orbit. That, in turn, helped researchers refine the estimated distance to Cygnus X-1.
    The new observations suggest that Cygnus X-1 is about 7,200 light-years from Earth, rather than the previous estimate of about 6,000 light-years. This implies that the star in Cygnus X-1 is even brighter, and therefore bigger, than astronomers thought. The star weighs about 40.6 suns, the researchers estimate. The black hole must also be more massive in order to explain its gravitational tug on such a massive star. The black hole weighs about 21.2 suns — much heftier than its previously estimated 14.8 solar masses, the scientists say. 
    The new mass measurement for Cygnus X-1’s black hole is so big that it challenges astronomers’ understanding of the massive stars that collapse to form black holes, says study coauthor Ilya Mandel, an astrophysicist at Monash University in Melbourne, Australia.
    “Sometimes stars are born with quite high masses — there are observations of stars being born with masses of well over 100 solar masses,” Mandel says. But such enormous stars are thought to shed much of their weight through stellar winds before turning into black holes. The bigger the star and the more heavy elements it contains, the stronger its stellar winds. So in heavy element–rich galaxies such as the Milky Way, big stars — no matter their starting mass — are supposed to shrink down to about 15 solar masses before collapsing into black holes.
    Cygnus X-1’s 21-solar-mass black hole undermines that idea.
    The LIGO and Virgo gravitational wave detectors have discovered black holes weighing tens of solar masses in other galaxies (SN: 1/21/21). But that is probably because LIGO peers at distant galaxies that existed earlier in the universe, Joseph says. Back then, fewer heavy elements existed, so stellar winds were weaker. With the new Cygnus X-1 measurement, “now we have to say, hang on, we’re in a [heavy element]–rich environment compared to the early universe … but we still managed to make this really massive black hole,” she says, “so maybe we’re not losing as much mass through stellar winds as we initially thought.” More

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    in Humans

    Oldest evidence of malted barley shows ancient Scandinavians made beer

    By Joshua Rapp Learn
    Carbonised barley malt from the Viking Age settlement at Hundborg in northern Jutland
    Peter Steen Henriksen/National Museum of Denmark
    Ancient malted barley grains have revealed that Danes were likely brewing beer and raising their drinking horns at least two millennia ago.
    The oldest known beers in the world trace back to the beginning of agriculture in the Middle East. In Scandinavia, the oldest evidence of beer is based on residue in a bark bucket from roughly 1370 BC which was found in the grave of a Bronze Age teenager known as the Egtved Girl. But chemical analysis shows that beer … More

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    in Humans

    Don’t Miss: Capitalism vs environmentalism at London’s Science Museum

    PixabayExplore
    Is Capitalism Compatible With Environmentalism asks broadcaster Jon Snow of a panel of experts in climate science, policy and economics at the Science Museum in London. Watch online at 7.30 pm on 26 February.

    Read
    Hidden Wonders are revealed by French physicist étienne Guyon and his co-authors in a fascinating book that explores the mathematical elegance in everyday objects and physical mechanisms, from crumpled paper to sandcastles.
    Courtesy of EPIX
    Watch
    Pennyworth, on Amazon Prime Video from 28 February (StarzPlay subscription required), starts its second counterfactual season with Batman’s future butler still in the UK, embroiled in a devastating civil war.
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    in Humans

    Do telomere length tests really reveal your biological age?

    Curiosity about how well our bodies are ageing has fuelled an industry around telomere length tests, but the much touted “biological clock” in our DNA isn’t what we thought

    Life 17 February 2021
    By Marta Zaraska
    Martin Leon Barreto

    WHEN David Nurse turned 30, he wanted to find out how his biological age compared with his chronological one. A life coach with the US National Baseball Association, he hoped that the ultra-healthy lifestyle he advocates to players had kept his own body young and healthy, too. So he took a test to assess the length of his telomeres. It revealed his biological age to be 28 years. That was in 2017. Two years later, he took another test. “I was down to 25, so that was great,” he says.
    If you google “telomeres”, you are likely to find them described as an ageing clock. They are segments of DNA at the ends of each chromosome that become shorter every time a cell divides. If this shortening happens slowly, it suggests that your body is wearing well. Say you are a 60-year-old with telomeres as long as those of an average 50-year-old, your mortality risk is equivalent to that of someone 10 years younger – or so the story goes. Increasing numbers of people want this information, and many companies offer tests like the one Nurse took, together with various pills claimed to lengthen your telomeres and, in turn, your lifespan.
    If only it were that simple. We are now discovering that telomeres are an unreliable ageing clock, which raises questions about the validity of ageing tests based on them. The links between telomere length and lifestyle choices also aren’t as straightforward as we once thought. In fact, long telomeres can even be bad news. Nevertheless, there are some surprising ways we can look after our … More

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    in Space & Astronomy

    The number of Milky Way nova explosions per year has been pinned down

    Each year, astronomers discover nova explosions in the Milky Way that cause dim stars to flare up and emit far more light than the sun before they fade again. But our galaxy is so big and dusty that no one knows how many of these eruptions occur throughout its vast domain, where they fling newly minted chemical elements into space.
    Now, by detecting the explosions’ infrared light, which penetrates dust better than visible light does, Caltech astronomer Kishalay De and his colleagues have estimated how often these outbursts occur in the Milky Way. Knowing the nova rate is vital for determining how much these explosions have contributed to the galaxy’s chemical makeup by creating new elements.
    The updated tally puts the rate at 46, give or take 13, a year, the team reports January 11 at arXiv.org. Past estimates of the nova rate have ranged from just 10 a year to 300.
    A nova arises from a binary star — two stars circling each other. One is a white dwarf, a dense star that’s about as small as Earth but approximately as massive as the sun. After the white dwarf receives gas from its companion, the gas explodes, making the dim star shine brilliantly. The nova does not destroy the star, unlike a supernova, which marks a star’s death.
    After observing the sky from Palomar Observatory in California for 17 months, De and colleagues detected 12 nova explosions. Estimating the number of missed outbursts, the astronomers deduced the yearly nova rate. Their rate is similar to, but more precise than, one reported four years ago by Allen Shafter, an astronomer at San Diego State University who pegged the annual nova rate at between 27 and 81.
    “They’re doing a wonderful job,” says Bradley Schaefer, an astrophysicist at Louisiana State University in Baton Rouge, who notes that searching at infrared wavelengths is ideal for finding distant explosions obscured by the galaxy’s dust. “They have an awful lot of really good data.”
    The more precise rate helps firm up estimates for how much these explosions have altered the galaxy’s chemical composition. In this regard, it’s hard for a mere nova to compete with a supernova explosion, which, though rare, releases far more newly produced elements than a nova does. But if the annual nova rate is around 50, then certain scarce isotopes on Earth — such as lithium-7, carbon-13, nitrogen-15 and oxygen-17 — arose partially or mostly in nova explosions, says Sumner Starrfield, an astronomer at Arizona State University in Tempe who was not involved with this study. The blasts then spirited these isotopes away before additional nuclear reactions could destroy them. More

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    in Humans

    Stonehenge was built with bits of an older Welsh Stone Age monument

    By Alison George
    The arc of former standing stones at Waun Mawn
    A. Stanford
    The origins of Stonehenge have long been a mystery. Now new discoveries show that the iconic monument may have started as a stone circle in Wales that was then dismantled and rebuilt 280 kilometres away at its current location on Salisbury plain. This is the conclusion of a team of archaeologists who uncovered the remains of what appears to be Britain’s third-largest stone circle, in the Preseli hills of west Wales.
    Stonehenge was built in several different phases between about 3000 and 2000 BC, starting with a large circular ditch and bank together with a circle of 2-metre-high bluestones just inside. Later, these bluestones were moved, and bigger structures made from boulders known as sarsens were built.

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    In 2015, a team led by Mike Parker Pearson at University College London revealed that the bluestones were extracted from quarries in the Preseli hills, some 280 kilometres away in west Wales. The team then looked for evidence of stone monuments close to these quarries, as the Neolithic people who extracted Stonehenge’s bluestones might have constructed stone circles here too.
    The archaeologists excavated at a site called Waun Mawn, which had four large stones seemingly placed in an arc. They uncovered evidence of a further six holes that each originally held a stone, indicating that there had once been a stone circle with a large diameter at the site.
    “The arc did continue – that was a really important moment,” says Parker Pearson. Extrapolating from these positions, the team estimates that the completed circle probably had 30 to 50 stones, though arranged more haphazardly than the original bluestone circle at Stonehenge.

    A number of strands of evidence suggest that stones from Waun Mawn formed part of the original stone circle at Stonehenge. Dating studies showed that the Waun Mawn stone circle was created between 3600 and 3200 BC, a few hundred years before the first stages of construction at Stonehenge, and the types of stone at the two sites match.
    One of the stone holes at the Welsh site has an unusual pentagonal shape, similar in shape and size to that of bluestone 62 at Stonehenge. “It could have been in that hole. It’s not categorical proof, but it is really very suggestive,” says Parker Pearson.
    The sizes of the two circles also match. “There are only two Neolithic monuments in Britain with the same diameter of 110 metres, and that’s the outer ditch of Stonehenge and the Waun Mawn diameter,” he says. Stonehenge is famous for aligning with the midsummer solstice sunrise, and the new evidence at Waun Mawn suggests it had this alignment too.

    “It’s a really interesting study that shows some nice arguments for a link between both stone circles,” says David Nash at the University of Brighton, UK, who wasn’t involved with the excavations in Wales, but, who last year published a study identifying the origins of Stonehenge’s sarsens. For him, the clincher would be to conduct detailed geological analysis of stone fragments found at Waun Mawn to see if they are identical to those found at Stonehenge.
    Others are less convinced. “They’ve got a ragbag of stones and I’m rather sceptical of it being a stone circle,” says Tim Darvill at Bournemouth University, UK, who has carried out many studies of Stonehenge.
    Further excavations are planned at Waun Mawn to clarify the picture. But if Stonehenge was rebuilt from a Welsh stone circle, this could help explain why Neolithic people went to such lengths to construct the iconic megalithic monument. Studies of the isotopes in cremated remains of the earliest people interred at Stonehenge indicate that some of them probably came from west Wales. This has led Parker Pearson to conclude that Stonehenge was constructed to commemorate the ancestors of the original people who lived at Stonehenge.
    The Welsh excavations also shed light on the earliest story of the monument’s origins from 1136, when the chronicler Geoffrey of Monmouth wrote how Stonehenge was built from a dismantled stone circle in Ireland. It seems this tale had a grain of truth, says Parker Pearson.
    Journal reference: Antiquity, DOI: 10.15184/aqy.2020.239
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    in Humans

    Mini brains genetically altered with CRISPR to be Neanderthal-like

    By Ibrahim Sawal
    These mini brains contain a Neanderthal version of a certain gene
    UC San Diego Health Sciences
    Miniature brains grown in the lab are helping to reveal how modern humans survived when other hominins died out.
    Neanderthals and Denisovans are some of our closest relatives. They lived alongside us about 50,000 years ago when modern humans migrated from Africa towards Europe, but they went extinct shortly after we came into contact with them. This might be because modern humans outcompeted and outsmarted them, but it may have just been bad luck.

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    Alysson Muotri at the University of California, San Diego, and his colleagues wanted to know more about how our brains differed from these other hominins and whether this could affect survival. The team compared the genomes of modern humans, Neanderthals and Denisovans and found a total of 61 genes that differed.
    One gene, neuro-oncological ventral antigen 1 (NOVA1), particularly caught their eye. The gene is specifically active during brain development and influences the developing nervous system. The team found that the modern human NOVA1 gene differed from the Neanderthal and Denisovan version by a single base pair
    To find out more, the team grew their own ancient human-like brains. They used CRISPR genome editing to change the modern NOVA1 gene in human stem cells to mimic the Neanderthal and Denisovan version, then prompted the cells to develop into a Neanderthal or Denisovan-like brain organoid – a small, simplified version of the organ consisting of clusters of brain cells in a dish. They did the same with standard human stem cells.

    As they matured, the ancient human organoids were smaller in diameter, had a more wrinkled cell surface and their cells multiplied more slowly than the modern human ones. “They are quite distinct from modern humans, suggesting that single base alteration can change brain development,” says Muotri.
    This alteration also changed the expression of 277 genes compared with the modern human organoids, and caused 113 alternative splicing events – a process that causes one gene to code for multiple proteins, many of which were linked to brain development and synapse formations.
    “The fact that virtually all modern humans now carry the modern version of the gene, strongly suggests that the alteration is a benefit to our species,” says Muotri. “If I might speculate, it might suggest that individuals carrying the Neanderthal NOVA1 alteration have a potential different way to process information,” he says, and this therefore may have affected their survival.

    Tony Capra at the University of California, San Francisco, says he is excited about these new methods because it allows us to directly test Neanderthal brains. “As it progresses, we will be able to evaluate how the Neanderthal genome worked in more and more complex and realistic models,” he says.
    However, because Muorti and his team used a modern human genome with a single change, Capra says this doesn’t truly reflect the entire Neanderthal or Denisovan genome. “It is unlikely that a single “magic” genetic change produced a dramatic positive change in these traits,” says Capra. He says there are many parts of our genome that contribute to cognition and that evolution may have acted on multiple variants with smaller effects.
    Journal reference: Science, DOI: 10.1126/science.aax2537
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    in Humans

    Listen to the oldest known conch shell horn from 18,000 years ago

    By Karina Shah

    A conch shell found in a cave used by the Magdalenian people of the late Upper Palaeolithic was originally thought to be a cup, but a new analysis suggests they used it as a kind of horn. That would make it the earliest known conch shell horn.
    Gilles Tosello at the University of Toulouse in France and his colleagues were investigating objects and cave art found in Marsoulas Cave in the Pyrenees mountains. They revisited a conch shell that was discovered in 1931.
    The shell is 31 centimetres long and 18 centimetres wide and once belonged to a large sea snail of the species Charonia lampas that likely lived on the coast of France or Spain.
    It has a small narrow hole drilled into the the point of the shell called the apex, and is decorated with fingerprint-shaped ochre red markings.

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    “We are pretty sure that this shell was transformed by human action, on the contrary to what was first published in the 1930s,” said Tosello at a press conference on 9 February. Its original discoverers suspected the conch shell was a ceremonial drinking cup.
    Tosello and his team came to a different conclusion after examining the inside of the shell with CT scanning and a tiny medical camera.
    “The broken part of the apex is very narrow, and the hole inside is perfectly round with a regular edge,” he said. The hole in the apex was most likely drilled to make way for some kind of mouthpiece, such as a small hollow bone to blow into, to protect the lips of the musician.

    To test the hypothesis that this was used as an instrument, the team enlisted the help of a horn player to see if they could play the conch shell – the horn player produced three notes close to C, D and C sharp.

    Along with the decorative ochre markings – which match paintings found on the walls of the original cave – there are smears of a brown, organic residue around the conch shell. Although there is not enough to determine what the residue is, it was probably used as a sort of glue to fix the mouthpiece into the shell, says Tosello.
    The team have now produced a 3D model of the conch shell to investigate how it was used by the Magdalenian people as a musical instrument, without damaging the original artefact.
    It’s not surprising that the Magdalenian people played instruments as music is an inherent part of any cultural system, says Francesco d’Errico at the University of Bordeaux in France.
    Journal reference: Science Advances, DOI: 10.1126/sciadv.abe9510
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