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New Galaxy Discovered That's Light on Dark Matter

posted by takyon on Monday April 01 2019, @09:35PM   Printer-friendly
from the gaaarlaktus dept.

An Anonymous Coward writes:

From New Atlas:

Some of the strongest evidence for dark matter to date has been discovered – and ironically, that's thanks to its absence. In a pair of studies published this week, astronomers have shed new light on dark matter through close observation of a galaxy previously found to have very little of the stuff, while the same team found a new example of a similar oddball galaxy.

It's generally believed that galaxies are held together through the gravitational influence of clumps of dark matter, so to find a galaxy with little to no dark matter was a surprise. And while it might sound like a strike against the theory, it actually ends up supporting it.

A Second Galaxy Missing Dark Matter in the NGC 1052 Group (DOI: 10.3847/2041-8213/ab0d92) (DX)

Still Missing Dark Matter: KCWI High-resolution Stellar Kinematics of NGC1052-DF2 (DOI: 10.3847/2041-8213/ab0e8c) (DX)

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  • (Score: 2) by FatPhil on Tuesday April 02 2019, @07:35PM (3 children)

    by FatPhil (863) <{pc-soylent} {at} {asdf.fi}> on Tuesday April 02 2019, @07:35PM (#823750) Homepage
    Agree, apart from this:

    > We already know general relativity is a massive deviation from Newtonian dynamics at cosmological scales.

    The bulk of what we can see out there that is interacting gravitationally with each other isn't travelling anything like relativistic speeds in any of their reference frames, so the deviations from Newton are pretty tiny - smaller than the error bars around any measurements we make. The things receding from us with enormous relative velocities are not interacting with us gravitationally at all, so the deviations are effectively zero.
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  • (Score: 1) by khallow on Wednesday April 03 2019, @12:54PM (2 children)

    by khallow (3766) Subscriber Badge on Wednesday April 03 2019, @12:54PM (#824053) Journal
    The bulk of what we see out there is more than a couple billion light years away from us. MOND might explain most galactic motion, but there's higher level motion as well.

    • (Score: 2) by FatPhil on Wednesday April 03 2019, @08:44PM (1 child)

      by FatPhil (863) <{pc-soylent} {at} {asdf.fi}> on Wednesday April 03 2019, @08:44PM (#824233) Homepage
      The bulk of what we see out there is more than a couple billion light years away from us and behaving almost exactly as Newtonian Dynamics would predict it to.
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      • (Score: 1) by khallow on Wednesday April 03 2019, @11:16PM

        by khallow (3766) Subscriber Badge on Wednesday April 03 2019, @11:16PM (#824289) Journal

        The bulk of what we see out there is more than a couple billion light years away from us and behaving almost exactly as Newtonian Dynamics would predict it to.

        Sorry, not with respect to mass that's far away. Newtonian dynamics, for example, would have instantaneous interactions between widely separated superclusters of galaxies not billions of years of lag. Cosmological inflation and the current observation of "negative energy" (which really is just observed current stretching of the universe).