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posted by Fnord666 on Thursday August 20 2020, @10:52PM   Printer-friendly
from the get-one-while-it's-hot dept.

The Universe Has Made Almost All the Stars It Will Ever Make:

But there's a big puzzle here. Exactly what puts a cap on the number of stars the universe has made and will ever make? This question has long been a subject of intense astrophysical debate, particularly in relation to the stellar composition of individual galaxies. For example, our current cosmological paradigm (or at least the one that most scientists subscribe to) is that we live in a universe dominated by dark matter, and in a dark matter universe the biggest galaxies should have formed the most recently,4 being assembled by the hierarchical, gravitationally driven merger of smaller systems. Yet if you examine very large, massive galaxies you find that they tend to be composed of older stars, suggesting that they've already sat around in their dotage for a very long time.

To try to explain this, astronomers invoke the idea of "quenching," where something acts to suppress or shut down the formation of new stars across galaxies. Not surprisingly, you need a pretty potent mechanism to quench anything on these scales, and among the most plausible culprits are the supermassive black holes that exist at the core of most galaxies and which can flood the space around them with photons and particles emitted from material as it screeches toward their event horizons. That outward transfer of energy can, quite literally, blow away the interstellar gas that would otherwise cool and clump into new stars.

The precise details of how this might work are certainly not yet fully understood. But there are new tantalizing clues in the fact that the masses of supermassive black holes appear to correlate with the mass of stars contained in their host galaxies.5 That is pretty shocking because even a supermassive black hole a billion times the mass of our sun only occupies a volume similar to that of our solar system. So somehow a galaxy that spans tens of thousands of light-years is intimately related to what is, in effect, a microscopic dot at its center.


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  • (Score: 2, Informative) by khallow on Friday August 21 2020, @01:18AM (1 child)

    by khallow (3766) Subscriber Badge on Friday August 21 2020, @01:18AM (#1039649) Journal

    How many hundreds of billions have been spent on looking for evidence of dark matter and there is none?

    Neutrinos are an obvious counterexample. We've found dark matter with the right sort of characteristics. We just haven't found enough.

    We may never find enough dark matter, because it isn't there in the necessary quantity, but it's a far cry from finding none at all.

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  • (Score: 1) by fustakrakich on Friday August 21 2020, @05:24AM

    by fustakrakich (6150) on Friday August 21 2020, @05:24AM (#1039779) Journal

    :-) When you travel at or near the speed of light, all that "dark" matter will light up! Bigger than Times Square!

    It's a Doppler thing

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