Carbon Chemist

Tag: dark matter

  • How could we give boring blobby galaxies a new, exciting shape?

    How could we give boring blobby galaxies a new, exciting shape?

    [ad_1]

    Dead Planets Society is a podcast that takes outlandish ideas about how to tinker with the cosmos – from snapping the moon in half to causing a gravitational wave apocalypse – and subjects them to the laws of physics to see how they fare. Listen on Apple, Spotify or on our podcast page.

    For the most part, galaxies only come in two shapes: spirals and blobs. While spirals can be majestic viewed from the right angles, the lack of variety can get boring over the cosmic eons. So in this episode of Dead Planets Society, it’s time to spice things up, galactically.

    Our hosts Leah Crane and Chelsea Whyte are joined by Vivian U at the University of California, Irvine, an astronomer who studies how galaxies evolve when they smash together and warp one another. In the real world, galactic collisions can create strange swirls and many-armed behemoths, but over time the chaos from the smash-up results in just another blob. To make a lasting change, we’ll need tools with a bit more precision.

    That’s where the supermassive black holes come in. They might be able to carve gaps through the dust and gas of a galaxy, creating more detailed images. But gravity tends to complicate things, and eventually even those black holes would devour too much matter and merge together, resulting in yet another blob. Perhaps dark matter could be used instead to create an invisible scaffold that shapes the distribution of the regular matter that we can see.

    Building such a strange-shaped galaxy – especially one unlike anything that a natural galactic collision would create, such as a galaxy with sharp corners or one in a recognisable image like a giraffe – might be a way to signal to aliens or future astronomers that we are here and we have incredible cosmic powers.

    In fact, perhaps this has already been done to the Milky Way by some strange alien force – after all, we can’t see our home galaxy from outside of it. We only know its shape by counting the stars that we can see in each direction and building theoretical models, so we can rule out that our galaxy is in the shape of a giraffe or something else wildly out of the ordinary. But if it were, say, a square instead of a spiral, it might be difficult for astronomers to tell the difference.

    Topics:

    [ad_2]

    Source link

  • Invisible ‘dark radiation’ may explain a big problem with dark energy

    Invisible ‘dark radiation’ may explain a big problem with dark energy

    [ad_1]

    A slice through the largest 3D map of our universe to date

    A slice through the largest 3D map of our universe to date

    laire Lamman/DESI collaboration

    There are hints that the universe may be behaving unexpectedly, and astrophysicists are racing to explain why. Their ideas to account for the surprising result include allowing dark matter and dark energy to interact, and arguing for the existence of strange “dark radiation” that is similar in nature to regular light but invisible.

    In April, researchers using the Dark Energy Spectroscopic Instrument (DESI) in Arizona released the biggest 3D map of the universe ever created, and it hinted…

    [ad_2]

    Source link

  • A new approach to dark matter could help us solve galactic anomalies

    A new approach to dark matter could help us solve galactic anomalies

    [ad_1]

    Dark matter halos (yellow) form around galaxies

    Ralf Kaehler/SLAC National Accelerator Laboratory

    Delicate might not be the first word that springs to mind when you think of the Milky Way. But when Mariangela Lisanti started tinkering with the recipe for our galaxy, she found it surprisingly fragile.

    Lisanti, a particle physicist at Princeton University, was simulating what would happen if dark matter – the mysterious stuff thought to account for over 80 per cent of all the matter in the universe – was more exotic than researchers typically assume. She swapped a small fraction of standard dark matter with something more complex. “We thought, we’re only adding 5 per cent, everything will be fine,” she says. “And then we just broke the galaxy.”

    There is good reason for such meddling. Since the 1980s, astronomical signs have pointed towards dark matter being a single type of slow-moving particle that doesn’t interact with itself. Particle physicists have gone to great lengths to search for that particle. But decades later, it remains a no-show – perhaps because dark matter isn’t how we have tended to imagine it.

    Recently, a series of galactic anomalies has sparked a scramble to explore alternatives. This “complex” dark matter might be as simple as sub-atomic particles that bounce off each other, or as complicated as families of dark particles that form dark atoms, stars and even galaxies. There is a daunting variety of possibilities.

    But now, observations of anomalies in our galaxy finally promise to help us narrow down the options. And with…

    [ad_2]

    Source link

  • The galactic anomalies hinting dark matter is weirder than we thought

    The galactic anomalies hinting dark matter is weirder than we thought

    [ad_1]

    Dark matter halos (yellow) form around galaxies

    Ralf Kaehler/SLAC National Accelerator Laboratory

    Delicate might not be the first word that springs to mind when you think of the Milky Way. But when Mariangela Lisanti started tinkering with the recipe for our galaxy, she found it surprisingly fragile.

    Lisanti, a particle physicist at Princeton University, was simulating what would happen if dark matter – the mysterious stuff thought to account for over 80 per cent of all the matter in the universe – was more exotic than researchers typically assume. She swapped a small fraction of standard dark matter with something more complex. “We thought, we’re only adding 5 per cent, everything will be fine,” she says. “And then we just broke the galaxy.”

    There is good reason for such meddling. Since the 1980s, astronomical signs have pointed towards dark matter being a single type of slow-moving particle that doesn’t interact with itself. Particle physicists have gone to great lengths to search for that particle. But decades later, it remains a no-show – perhaps because dark matter isn’t how we have tended to imagine it.

    Recently, a series of galactic anomalies has sparked a scramble to explore alternatives. This “complex” dark matter might be as simple as sub-atomic particles that bounce off each other, or as complicated as families of dark particles that form dark atoms, stars and even galaxies. There is a daunting variety of possibilities.

    But now, observations of anomalies in our galaxy finally promise to help us narrow down the options. And with…

    [ad_2]

    Source link

  • We live in a cosmic void so empty that it breaks the laws of cosmology

    We live in a cosmic void so empty that it breaks the laws of cosmology

    [ad_1]

    New Scientist Default Image

    ryan wills; Klaus Vedfelt/Getty Images

    EVER feel like you are stuck in a hole? Newsflash: you are. Astronomers call it the “local hole”, but that is quite the understatement. It is vast, gigantic, enormously huge – although, in truth, adjectives fail us when it comes to this expanse of nothingness. It is the largest cosmic void we know of, spanning 2 billion light years. Our galaxy happens to be near its centre, but the trouble with this hole isn’t that it presents a proximate danger – more that it shouldn’t exist at all.

    That is, if one of our most firmly held beliefs about the cosmos is true. That assumption, known as the cosmological principle, says that the universe’s matter should be evenly distributed on the largest scales. It is the cornerstone on which much of modern cosmology is built. If the void is real, then that stone might be crumbling.

    For this reason, few dared to believe the void could be genuine. But evidence has mounted in recent years, and astronomers have moved from doubt to begrudging acceptance. They have also discovered other similarly vast structures. So now the question is being asked with increasing urgency: if we really are living in a void, do we need to drastically modify our models of the cosmos? That might involve rethinking gravity, the nature of dark matter, or both.

    The idea that the universe has the same character through and through can be traced back at least as far as Isaac Newton. He argued that the motions of the stars and planets can be explained…

    [ad_2]

    Source link

  • Astronomers have found what may be the smallest galaxy ever

    Astronomers have found what may be the smallest galaxy ever

    [ad_1]

    This deep sky image (left) contains a star cluster (right) that could be the faintest and smallest galaxy ever seen

    CFHT/S. Gwyn (right) / S. Smith (left)

    An impossibly small clump of stars is orbiting the Milky Way without breaking apart, which could mean it is the least massive galaxy ever spotted. Although it only contains about 57 stars, it may be chock-full of dark matter.

    The strange cluster, called Ursa Major III/UNIONS 1, orbits our galaxy about 33,000 light years from the solar system. It is the smallest and faintest satellite of the Milky Way…

    [ad_2]

    Source link

  • Rethinking space and time could let us do away with dark matter

    Rethinking space and time could let us do away with dark matter

    [ad_1]

    Post-quantum gravity could explain the rotation speed of galaxies, which is normally seen as evidence for dark matter

    NASA, ESA, CSA

    A potential new theory of gravity that ruffles the fabric of the universe, allowing space and time to vary erratically, could solve some of the largest mysteries in physics and do away with the need for dark matter, say its proponents. However, others say much more evidence is needed before this “post-quantum gravity” can be taken seriously.

    Most cosmologists believe…

    [ad_2]

    Source link

  • There’s a New Theory About Where Dark Matter Is Hiding

    There’s a New Theory About Where Dark Matter Is Hiding

    [ad_1]

    But there may be opportunities to indirectly spot the signatures of those gravitons.

    One strategy Vafa and his collaborators are pursuing draws on large-scale cosmological surveys that chart the distribution of galaxies and matter. In those distributions, there might be “small differences in clustering behavior,” Obied said, that would signal the presence of dark gravitons.

    When heavier dark gravitons decay, they produce a pair of lighter dark gravitons with a combined mass that is slightly less than that of their parent particle. The missing mass is converted to kinetic energy (in keeping with Einstein’s formula, E = mc2), which gives the newly created gravitons a bit of a boost—a “kick velocity” that’s estimated to be about one-ten-thousandth of the speed of light.

    These kick velocities, in turn, could affect how galaxies form. According to the standard cosmological model, galaxies start with a clump of matter whose gravitational pull attracts more matter. But gravitons with a sufficient kick velocity can escape this gravitational grip. If they do, the resulting galaxy will be slightly less massive than the standard cosmological model predicts. Astronomers can look for this difference.

    Recent observations of cosmic structure from the Kilo-Degree Survey are so far consistent with the dark dimension: An analysis of data from that survey placed an upper bound on the kick velocity that was very close to the value predicted by Obied and his coauthors. A more stringent test will come from the Euclid space telescope, which launched last July.

    Meanwhile, physicists are also planning to test the dark dimension idea in the laboratory. If gravity is leaking into a dark dimension that measures 1 micron across, one could, in principle, look for any deviations from the expected gravitational force between two objects separated by that same distance. It’s not an easy experiment to carry out, said Armin Shayeghi, a physicist at the Austrian Academy of Sciences who is conducting the test. But “there’s a simple reason for why we have to do this experiment,” he added: We won’t know how gravity behaves at such close distances until we look.

    The closest measurement to date—carried out in 2020 at the University of Washington—involved a 52-micron separation between two test bodies. The Austrian group is hoping to eventually attain the 1-micron range predicted for the dark dimension.

    While physicists find the dark dimension proposal intriguing, some are skeptical that it will work out. “Searching for extra dimensions through more precise experiments is a very interesting thing to do,” said Juan Maldacena, a physicist at the Institute for Advanced Study, “though I think that the probability of finding them is low.”

    Joseph Conlon, a physicist at Oxford, shares that skepticism: “There are many ideas that would be important if true, but are probably not. This is one of them. The conjectures it is based on are somewhat ambitious, and I think the current evidence for them is rather weak.”

    Of course, the weight of evidence can change, which is why we do experiments in the first place. The dark dimension proposal, if supported by upcoming tests, has the potential to bring us closer to understanding what dark matter is, how it is linked to both dark energy and gravity, and why gravity appears feeble compared to the other known forces. “Theorists are always trying to do this ‘tying together.’ The dark dimension is one of the most promising ideas I have heard in this direction,” Gopakumar said.

    But in an ironic twist, the one thing the dark dimension hypothesis cannot explain is why the cosmological constant is so staggeringly small—a puzzling fact that essentially initiated this whole line of inquiry. “It’s true that this program does not explain that fact,” Vafa admitted. “But what we can say, drawing from this scenario, is that if lambda is small—and you spell out the consequences of that—a whole set of amazing things could fall into place.”

    Original story reprinted with permission from Quanta Magazine, an editorially independent publication of the Simons Foundation whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.

    [ad_2]

    Source link

  • Dark stars may be waiting in a mirror universe for us to discover them

    Dark stars may be waiting in a mirror universe for us to discover them

    [ad_1]

    Physicists have proposed that a mirror universe alongside our own might explain dark matter ­– and we might be able to see traces of its stars

    [ad_2]

    Source link