In an article today in the Guardian, science correspondent Hannah Devlin
reports on the claims of two separate teams of scientists that they have
indirect evidence that accounts for half the missing matter in the Universe.
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Originally Posted by Hannah Devlin, the Guardian
It is one of cosmology’s more perplexing problems: that up to 90% of the ordinary matter in the universe appears to have gone missing.
Now astronomers have detected about half of this missing content for the first time, in a discovery that could resolve a long-standing paradox.
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Originally Posted by Hannah Devlin, the Guardian
The deficit is known as the “missing baryon problem”, baryons being ordinary subatomic particles like protons and neutrons.
Richard Ellis, a professor of astrophysics at the University College London, said: “People agree that there’s a lot missing, raising the question where is it?”
The distribution of galaxies in the universe follows a web-like pattern and scientists have speculated that the missing baryons could be floating in diffuse gaseous filaments and sheets linking the galaxy clusters in the cosmic web.
Theoretical calculations suggest these gaseous threads, known as the warm–hot intergalactic medium, or the Whim, ought to be around a million degrees Celsius. A mist of gas at this temperature is too cold to emit X-rays that could be spotted by ordinary telescopes from the Earth – but not cold enough to absorb significant amounts of light passing through it.
“The trouble is, it’s in this unusual temperature regime where we can’t see it,” said Ellis.
Now two separate teams of scientists, one at the University of Edinburgh, the other at the Institute of Space Astrophysics in Orsay, France, have produced compelling indirect evidence for the Whim. Both teams relied on the fact that when radiation travels through a hot gas, it is scattered, meaning that the Whim ought to appear as a dim outline in the cosmic microwave background.
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Quote:
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Originally Posted by Hannah Devlin, the Guardian
The Edinburgh team found the regions between galaxies appeared to be about six times as dense as the surrounding bits of space and when summed up, these gaseous threads could amount to about 30% of the ordinary matter in the universe. The French teams’ calculation came out at slightly less than this, but the numbers are consistent.
Ellis, who was not involved in either project, describes the findings as “inspirational”. “These two papers have been very prominently discussed and people are excited,” he added. “The Whim is out there.”
The initial measurements still do not account for all the ordinary matter, and some believe the remaining portion could be made up by exotic unobserved objects such as black holes or dark stars. Cosmologists are also still yet to discover the nature of dark matter, which makes up even more of the universe.
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Article here :-
https://www.theguardian.com/science/...n-the-universe
Papers
"Missing baryons in the cosmic web revealed by the Sunyaev-Zel’dovich effect", de Graaff et. al. University of Edinburgh
https://arxiv.org/pdf/1709.10378v1.pdf
"A Search forWarm/Hot Gas Filaments Between Pairs of SDSS
Luminous Red Galaxies", Tanimura et.al. University of British Columbia et. al.
https://arxiv.org/pdf/1709.05024.pdf