Philippa Kaur

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    in Space & Astronomy

    The Milky Way makes little galaxies bloom, then snuffs them out

    If you’re a small galaxy and want to mint new stars, come to the Milky Way — but don’t get too close if you want a long-lasting star-making career. New observations with the Gaia space telescope show that our galaxy is both friend and foe to the lesser galaxies that revolve around it.
    Some 60 known galaxies orbit the Milky Way. About a dozen of these satellite galaxies are dim dwarf spheroidals, which each emit just 0.0005 to 0.1 percent as much light as the Milky Way (SN: 12/22/14). Their few stars are spread out from one another, giving the galaxies such a ghostly appearance that the first one found was initially suspected to be only a fingerprint on a photographic plate.
    But these ghostly galaxies once sparkled with young stars. A new study finds that most of these galaxies lit up when they first crossed into our galaxy’s gravitational domain as fresh stars arose. But then, in most cases, the little galaxies stopped making stars soon afterward, because the Milky Way stripped the dwarf galaxies of gas, the raw material for star formation.
    Astronomer Masashi Chiba of Tohoku University in Sendai, Japan, and his then-graduate student Takahiro Miyoshi studied seven of the dwarf spheroidal galaxies orbiting the Milky Way. The researchers used the European Space Agency’s Gaia spacecraft, which had measured the galaxies’ motions, to compute their orbits around the Milky Way’s center. The orbits are elliptical, so the galaxies approach and then recede from our galaxy’s center. The astronomers then compared those paths to the times when the galaxies formed their stars.

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    “We found that there’s a very nice coincidence between the timing of the first infall of the satellite [toward the Milky Way] and the peak in the star formation history,” Chiba says. In work posted online at arXiv.org on October 23, the astronomers attribute the burst of star formation in the small galaxies to the Milky Way. Encountering the giant galaxy squeezes the dwarf galaxies’ gas, causing that gas to collapse and spawn lots of new stars.
    As an example, the Draco dwarf galaxy first crossed into the Milky Way’s domain 11 billion years ago and formed numerous stars then — but never again. More recently, the Leo I dwarf galaxy entered our galaxy’s realm just 2 billion years ago, a time that coincided with its last burst of star birth. But today Leo I creates no new stars and, like Draco, has no gas to do so.
    Dwarf galaxies that kept their distance also kept their gas longer, the researchers found. The galaxies that came closest to the Milky Way’s center, such as Draco and Leo I, ceased all star formation soon after crossing the Milky Way’s frontier. However, the galaxies that entered our galaxy’s domain but remained farther out, such as Fornax and Carina, fared better.
    “Those two galaxies kept their interstellar gas inside them, so that the star formation still continued,” Chiba says. Both galaxies managed to eke out new stars for many billions of years after crossing into the Milky Way’s realm. Today, however, neither galaxy has any gas left.
    “I think it all makes sense,” says Vasily Belokurov, an astronomer at the University of Cambridge, who notes how essential the Gaia spacecraft was to the discovery. “It’s a beautiful demonstration of what we’ve never been able to do before Gaia, and suddenly we can do these magical things.” More

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    in Humans

    Tumble review: A brilliant science podcast for children of all ages

    When inundated with disinformation, conspiracy theories and total nonsense, how can children learn about science? By listening to Tumble, a fantastic family podcast

    Humans 4 November 2020
    By Simon Ings
    Tumble is a science podcast aimed at children, but parents will enjoy it too
    Getty Images/Johner RF

    Tumble
    Tumble Science Podcast for Kids

    SHOULD we teach our children scientific facts about the world, or should we teach them to do science?
    The answer, obviously, is both. Yet when physics, chemistry and biology struggle for independent spaces in the school timetable, it may be too much to hope that, along with the facts, children are being given any real idea of what science is like.
    Teaching both the letter and spirit of science has always been difficult. I only acquired a … More

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    in Humans

    Don't Miss: Why laughter is contagious and being funny makes us sexier

    ReadThe Comedy of Error has evolutionary ecologist Jonathan Silvertown sharing old jokes and the latest science in his account of how humour evolved, why laughter is contagious and how being funny makes us sexier.

    Being Human

    Visit
    Being Human, the University of London’s annual festival of the humanities, moves partly online this year with digital exhibitions, workshops, quizzes, talks and debates from 12 to 22 November. This year’s theme is “New Worlds”.
    Listen
    The Seekers Podcast, a playful and interactive series from theatre group The Wardrobe Ensemble, lets children aged 3 to 8 and their families join explorers … More

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    in Humans

    Truth Seekers review: Ghost-hunting capers from Shaun of the Dead duo

    Amazon Prime’s Truth Seekers from Sean of the Dead duo Simon Pegg and Nick Frost is a mash up of British comedy and ghost hunting. Let’s hope the series becomes today’s Ghostbusters, says Emily Wilson

    Humans 4 November 2020
    By Emily Wilson
    Elton (Samson Kayo, left) and Gus (Nick Frost) hunt ghosts
    Colin Hutton/Stolen Pictures/Amazon Studios

    Truth Seekers
    Jim Field Smith
    Amazon Prime Video
    COMEDY duo Simon Pegg and Nick Frost have specialised at writing and starring in movies (Shaun of the Dead, The World’s End) that stir together warm, beautifully drawn British comedy and classic horror themes. Their latest outing, a TV series called Truth Seekers, arises from that same delightful tradition.
    The truth seekers of the title are a gang who rove around England investigating the paranormal. Given that, I queried with my editors at New Scientist why I … More

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    in Humans

    Wealthy US cities struggle to provide running water for all residents

    By Ian Morse
    Some residents of San Francisco are in water poverty
    Wenjie Dong/Getty Images

    Widening wealth gaps in some of the richest cities in the US have produced a rise in the number of households without running water.
    Public information suggests that about half a million households in the US – about 1.1 million people – live without piped water, which places them in “plumbing poverty”. Surveys also show that 73 per cent of these households are found in metropolitan areas.
    To investigate further, Katie Meehan at King’s College London – previously at the University of Oregon – and her colleagues analysed US census data, and information relating to the country’s 50 largest metropolitan areas collected during the government’s American Community Survey between 2013 and 2017.

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    This showed that San Francisco in California, Portland in Oregon and Austin in Texas are among the cities with the highest rates of plumbing poverty. New York, Los Angeles and San Francisco – among the wealthiest US cities – recorded the most overall residents without complete plumbing.
    Meehan and her colleagues say there is a strong connection between this plumbing poverty and growing income inequality in cities.

    They found that for every 10 per cent increase in income inequality in the 50 largest metropolitan areas, measured using a standard statistical metric called the Gini coefficient, households were 1.5 times more likely to lack “complete plumbing” – defined as a house supplied by both hot and cold piped water with a bath or shower used only by the occupants.
    “In areas that are characterised by income inequality, we see some of the highest rates of plumbing poverty,” says Meehan.
    What’s more, people without access to piped water were significantly more likely to be living in rented accommodation and to be using more than of a third of their income to pay rent.

    Urban households headed by black people were almost 35 per cent more likely to lack piped water compared with households headed by non-Hispanic white people.
    Although surveys suggest that there are almost half a million US households without water access, Meehan says this is likely to be an undercount, because census surveys routinely have trouble recording renters, the homeless, and black people.
    “I think that conditions of water access will actually deteriorate, and the places where I think it will get worse are not the places we may first think of, like the San Franciscos, the Portlands or the Los Angeleses,” she says.
    Focusing on individual cities and households will help reveal what exactly is causing water insecurity, says Meehan. “That’s the next step in research.”
    Journal reference: PNAS, DOI: 10.1073/pnas.2007361117
    More on these topics: More

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    in Space & Astronomy

    LIGO and Virgo’s gravitational wave tally more than quadrupled in six months

    Earth is awash in gravitational waves.
    Over a six-month period, scientists captured a bounty of 39 sets of gravitational waves. The waves, which stretch and squeeze the fabric of spacetime, were caused by violent events such as the melding of two black holes into one.
    The haul was reported by scientists with the LIGO and Virgo experiments in several studies posted October 28 on a collaboration website and at arXiv.org. The addition brings the tally of known gravitational wave events to 50.
    The bevy of data, which includes sightings from April to October 2019, suggests that scientists’ gravitational wave–spotting skills have leveled up. Before this round of searching, only 11 events had been detected in the years since the effort began in 2015. Improvements to the detectors — two that make up the Advanced Laser Interferometer Gravitational-Wave Observatory, or LIGO, in the United States, and another, Virgo, in Italy — have dramatically boosted the rate of gravitational wave sightings.

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    While colliding black holes produced most of the ripples, a few collisions seem to have involved neutron stars, ultradense nuggets of matter left behind when stars explode.
    Some of the events added to the gravitational wave register had been previously reported individually, including the biggest black hole collision spotted so far (SN: 9/2/20) and a collision between a black hole and an object that couldn’t be identified as either a neutron star or black hole (SN: 6/23/20).
    [embedded content]
    Gravitational waves are produced when two massive objects, such as black holes, spiral around one another and merge. These visualizations, which are based on computer simulations, show these merging objects for 38 of the 50 known gravitational wave events.
    What’s more, some of the coalescing black holes seem to be very large and spinning rapidly, says astrophysicist Richard O’Shaughnessy of the Rochester Institute of Technology in New York, a member of the LIGO collaboration. That’s something “really compelling in the data now that we hadn’t seen before,” he says. Such information might help reveal the processes by which black holes get partnered up before they collide (SN: 6/19/16).
    Scientists also used the smorgasbord of smashups to further check Albert Einstein’s theory of gravity, general relativity, which predicts the existence of gravitational waves. When tested with the new data — surprise, surprise — Einstein came up a winner. More

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    in Humans

    Carlo Rovelli’s new book: Eclectic essays on physics, history and more

    Carlo Rovelli’s bestsellers saw him dubbed the poet of physics and showed a mind seeking knowledge for its own sake. His new book, There Are Places in the World Where Rules Are Less Important Than Kindness, reminds us why we need more minds like his

    Space 28 October 2020
    By Richard Webb

    Victor Habbick Visions/Science Photo Library

    I APPROACHED Carlo Rovelli’s latest book with trepidation, bordering on dread. The Italian quantum gravity researcher’s previous bestsellers – Seven Brief Lessons on Physics, Reality Is Not What It Seems, The Order of Time – have seen him playing on home territory, where his lucid, lyrical touch won him a reputation as “the poet of physics”.
    But his new book’s title, There Are Places in the World Where Rules Are Less Important Than Kindness, suggested it might have gone … More