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Computer Simulations Point To the Source of Gravitational Waves (theverge.com) 126

An anonymous reader writes from a report via The Verge: On February 11th, scientists at the LIGO observatory made history when they announced the detection of the first gravitational waves. A new study says the gravitational waves likely came from two massive suns that formed about 12 billion years ago, or two billion years after the Big Bang. The researcher's calculations have been published today in the journal Nature, and were determined by running a complex simulation called the Synthetic Universe: a computer model that simulates how the Universe may have evolved since the start of the Big Bang. The simulation even includes a synthetic LIGO detector to determine the types of objects that the observatory would detect over time. The Synthetic Universe can also make predictions as it includes a mock-LIGO to chronologically sync when we detected the waves. If the model is correct, we should see LIGO pick up to 60 detections when it begins its next observation run this fall. It could hear up to 1,000 detections annually at its peak sensitivity. The lead study author Chris Belczynski speculates specifically the size of black hole mergers that the LIGO should be able to detect from gravitational waves, a combined mass between 20 and 80 times the mass of our sun, indicating that they're likely from soon after the Big Bang when stars had lower metal content and formed proportionately larger black holes. His model suggests that the ones that collided to make these gravitational waves were stars that formed 12 billion years ago, became black holes 5 million years later, and then merged 10.3 billion years after that.
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Computer Simulations Point To the Source of Gravitational Waves

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  • by Bugdanoff ( 1252042 ) on Thursday June 23, 2016 @05:52AM (#52372759)
    > "The simulation even includes a synthetic LIGO detector to determine the types of objects that the observatory would detect over time."
    Does the simulation also include a synthetic simulation in order to determine what it would find out by simulating the universe ?
  • What seems more interesting? When the stars that were the precursors to the blackholes were formed, or when the event actually happened? I would have much preferred seeing an emphasis on the fact that the event happened 1.7 billion years ago, rather than than the stars that originated the chain of events were formed 12 billion years ago...

    • by Anonymous Coward

      The idea is that right after the Big Bang very nearly equal amounts of anti-matter and matter were formed. These annihilated each other leaving just hydrogen clouds which formed massive stars which in turn rapidly went supernova and created black holes. Then these merge together ... and the gravitational waves create enough disturbance to allow more gas clouds to coalesce into stars.

      • Well, I didn't read that anywhere... Where can one read about that, the formation of matter and antimatter? And how is hydrogen the byproduct of that? I thought hydrogen was matter, not the leftovers of matter/antimatter?

        • Well, I didn't read that anywhere... Where can one read about that, the formation of matter and antimatter? And how is hydrogen the byproduct of that? I thought hydrogen was matter, not the leftovers of matter/antimatter?

          Hydrogen is matter and what we see around us in the leftovers of the original matter/antimatter created at the beginning of the universe. In this case, matter and anti-matter were created roughly equally from energy in the beginning of the universe. It all pretty much annihilated with each other and turned back into energy which formed matter and antimatter again. For some reason, matter had a slight edge, so after the anti-matter turned back into energy there was still matter left over, which caused the ne

    • Agreed. Maybe even a little context - assuming gravity waves propagate at the speed of light (consistent with the rate of energy loss we see in stellar binaries spinning down) 1.7 billion years ago translates to (roughly) 1.7 billion light years away, about 680 times further away than the Andromeda galaxy. Still practically next door in cosmic terms, so inflation isn't going to fudge the numbers too much.

      I'm not certain exactly how gravitational waves propagate, nor how energy levels correlate to geometri

      • That being the case, I've got to wonder exactly how insane the gravitational waves from a black hole merger are compared to the relatively steady fast-orbiting binary stars we can see via more traditional means? Are such waves theoretically too weak for us to detect with LIGO, or is it just that the signal-analysis is only looking for the distinctive "spike" from a black hole merger as a sort of low-hanging fruit to prove that gravity waves do in fact exist?

        LIGO is looking for both, the problem is that such binaries don't emit a high-amplitude pulse, which is easy to see over the noise, you need to integrate over a large set of data to get a statistically significant SNR. As a result, it takes a lot more work, so they haven't published any findings on that yet.

        Perhaps the more interesting question for me is, just how much will the proposed eLISA mission, with it's 250,000x longer arms (and I presume 250,000x greater sensitivity, plus much lower ambient noise levels) be able to detect? Being able to directionally detect the gravity waves from fast-orbiting binary stars, that we can then correlate with more traditional telescopy, could give us incredible insight into the workings of gravity waves including, in the case of binaries unmistakably spinning down, confirming whether the waves actually propagate at lightspeed.

        While eLISA is a really cool and important next step, the advantage isn't entirely greater sensitivity (it's strain sensitivity is actually less than LIGO [wikipedia.org]), it's that it can explore an entirely differe

  • His model suggests that the ones that collided to make these gravitational waves were stars that formed 12 billion years ago, became black holes 5 million years later, and then merged 10.3 billion years after that.

    Did he do his experiment 3.3 billion years in the future?

    Of course, it could just be a typo...

    • -12 + 0.005 + 10.3 ~= -1.7 Gya, 1.7e9 lightyear ~= 521Mpc, which fits within the 410 +160 -180 Mpc estimated distance.
    • LOL... the 5 was million, not billion. Misread on my part... }:-)

    • You missed that the middle number was million not billion.

      Stars formed 12 billion years ago.
      Stars collapsed to black holes 5 million (0.005 billion) years later.
      Black holes collided 10 billion years later.

      The waves were generated ~1.7 Billion years ago.

  • The way they are describing this phenomenon sounds like gravitational waves travel at a particular speed. I was hoping that they somehow broke the speed of light barrier so we could have zero-latency communication. Although I suppose they wouldn't be 'waves' if the effect of gravity was instantaneous...

    bummer... Although if the force of gravity is in step with the speed of light, there might be a correlation to be made about the nature of those two forces, one being cosmic one being quantum...

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