Yep that’s true scientist just detected half of the missing normal
matter in the Universe. “Everybody sort of knows that it has to be there, but
this is the first time that somebody – two different groups, no less – has come
up with a definitive detection,” says Ralph Kraft at the Harvard-Smithsonian
Center for Astrophysics in Massachusetts.
Observations of galaxies and galaxy clusters in the local universe can
account for only 10% of the baryon content -made of particles called baryons
rather than dark matter- inferred from measurements of the cosmic microwave
background and from nuclear reactions in the early Universe.
Locating the remaining 90% of baryons has been one of the major
challenges in modern cosmology. The missing links between galaxies have finally
been found. This is the first detection of the roughly half of the normal
matter in our universe – protons, neutrons and electrons – unaccounted for by
previous observations of stars, galaxies and other bright objects in space.
Models of the universe say there should be about twice as much ordinary
matter out there, compared with what we have observed so far. Now, two separate
teams found the missing matter – made of particles called baryons rather than
dark matter – linking galaxies together through filaments of hot, diffuse gas.
“The missing baryon problem is solved,” says Hideki Tanimura at the
Institute of Space Astrophysics in Orsay, France, leader of one of the groups.
The other team was led by Anna de Graaff at the University of Edinburgh, UK.
“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. “It’s been purely speculation until now.” Because it's not quite hot
enough for X-ray telescopes to observe.
Both teams took advantage of a phenomenon called the Sunyaev-Zel’dovich
effect that occurs when light left over from the big bang passes through hot
gas to find another way to definitively show that these threads of gas are
really there. As photons of light travel, some of them scatters off the electrons in
the gas, leaving a dim patch in the cosmic microwave background from the birth
of the cosmos that were to faint to be mapped by the Planck satellite in 2015.
Both teams selected pairs of galaxies from the Sloan Digital Sky Survey
that were expected to be connected by a strand of baryons. They stacked the
Planck signals for the areas between the galaxies, making the individually
faint strands detectable en masse.
Tanimura’s team stacked data on 260,000 pairs of galaxies, and de
Graaff’s group used over a million pairs revealing firm evidence of gas
filaments between the galaxies. Tanimura’s group found they were almost three
times denser than the mean for normal matter in the universe, and de Graaf’s group
found they were six times denser confirming that the gas in these areas is
dense enough to form filaments.
“We expect some differences because we are looking at filaments at
different distances,” says Tanimura. “If this factor is included, our findings are
very consistent with the other group.”
“This goes a long way toward showing that many of our ideas of how
galaxies form and how structures form over the history of the universe are
pretty much correct,” says Ralph Kraft.
Via DailyGalaxy