Berlin, May 7 : Astronomers have detected a part of the long-searched baryonic matter in space, which is the material out of which four percent of the Universe is composed.
This material was detected in a filament connecting two clusters of galaxies, by a team of astrophysicists from the Max Planck Institute for extraterrestrial Physics (MPE) and the ESO, in Garching, Germany.
The Universe is constructed like an oversized spider web: All visible material is arranged along the filamentary structure of the Dark Matter.
On its threads and knots, this web holds gigantic chunks of baryonic matter, which are made of quarks and leptons.
Studies of the Big Bang and the fluctuations of cosmic background radiation yield quite exact figures on the existence of baryons in the Universe.
So, from the calculations, astronomers knew for a long time that the vanished pieces of the cosmological puzzle must be hidden somewhere.
To trace and apprehend this solely observable component in the Universe is the precondition to learn more about the web of dark material and to test the quality of different cosmological models.
The missing part of the baryonic matter is imagined since nine years as hot, ultra-thin gas haze of very low density between larger structures.
Due to its high temperature, this gas is expected to emit primarily in the far-ultraviolet and X-ray band.
Scientists around Norbert Werner from SRON Netherlands Institute for Space Research therefore used the X-ray space observatory XMM-Newton to observe the two clusters of galaxies Abell 222 and Abell 223, which are connected by a filament.
This structure was chosen because of its fortunate geometry: The astronomers could look directly into the bridge instead of looking at it from the side.
The hot gas they found there is probably the hottest and densest part of the diffuse gas which constitutes half of the missing baryons in the Universe.
"Having discovered the hottest of the missing baryons is of particular importance as various models, while all predicting the lost matter in some kind of warm gas, tend to disagree about the extremes", explained Alexis Finoguenov from Max Planck Institute for Extraterrestrial Physics.
The discovery of the cosmic gas is a significant step forward on the way to a complete understanding of the cosmic evolution.
The distribution and composition of the baryonic matter gives information about what happened after the Big Bang and which forces are dominating the Universe today and in the future.