Welcome To CEAMIX BLOG: Science

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<li>Scientists produce indirect evidence of gaseous filaments and 
sheets known as Whims linking clusters of galaxies in the cosmic web</li>
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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. 
The conundrum first arose from measurements
 of radiation left over from the Big Bang, which allowed scientists to 
calculate how much matter there is in the universe and what form it 
takes. This showed that about 5% of the mass in the universe comes in 
the form of ordinary matter, with the rest being accounted for by dark 
matter and dark energy . 
Dark matter has never been directly 
observed and the nature of dark energy is almost completely mysterious, 
but even tracking down the 5% of ordinary stuff has proved more 
complicated than expected. When scientists have counted up all the 
observable objects in the sky – stars, planets, galaxies and so on – 
this only seems to account for between a 10th and a fifth of what ought 
to be out there. 
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 . 
The scientists overlaid observations of the cosmic background radiation, made by the 
Planck
 space observatory , and the most detailed three dimensional map of the 
cosmic web, created by the Sloane Digital Sky Survey (SDSS) . They 
hypothesised that if there were gas threads linking galaxy clusters, 
these should show up in the Planck data. 
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.