What's the Matter? Scientists Spot the Missing Part of the Universe
Oct 11 2017 by Michele Stevens
However, our observations of normal matter (protons, neutrons and electrons) only account for about 2.5 percent of the universe-the rest of it is nowhere to be found. Still, these simulations too predict that entire galaxies and planets in the universe are connected by long filaments of usual matter. Two groups of scientists though appear to have resolved this issue.
Two independent teams believe they have found that missing matter, made up of particles called baryons. The other team was led by Anna de Graaff at the University of Edinburgh, UK.
Until now, the matter just hasn't been hot enough to spot using X-ray, so the two teams, from France and the United Kingdom, had to come up with a new means of detecting it.
"There's no sweet spot - no sweet instrument that we've invented yet that can directly observe this gas", says Richard Ellis at University College London.
In order to detect the gasses, both teams used the Sunyaev-Zeldovich effect, a phenomenon which takes place after leftover photons of the Big Bang's glow pass through hot gas surrounding galaxy clusters; as a result, the photons leave behind a trace of the gas that can finally be captured.
The arguments of scientists based on the analysis of data obtained from the orbiting Planck Observatory, which is created to study the cosmic microwave background. As this light moves through hot gas, some of it scatters, leaving a patch in the CMB.
The researchers then stacked the signals from ESA's Planck space telescope for the areas between the galaxies so individual faint strands become detectable as a group.
Using data from the Planck satellite, the teams were able to combine galaxy data in bulk and compare them to see the tiny differences that might highlight these filaments.
With a total of 260,000 pairs of such galaxies already explored, it turned out that in filamentary structures between them, baryonic matter is several times denser than elsewhere in the universe. The first group discovered that these filaments were almost three times denser compared with the average of normal matter. Researcher Hideki Tanimura from the University of British Columbia said that the final results of both the teams varied because they were looking at filaments at different distances.
So the two groups had to find another way to definitively show that these threads of gas are really there.