European satellite spots some of universe's missing matter
Last Updated: Wednesday, May 7, 2008 | 1:55 PM ET
CBC News
Scientists in Germany and the Netherlands say the discovery of hot gas between two clusters of galaxies brings them a small step closer to understanding the matter that makes up the universe.
Astrophysicists using using the orbiting X-ray space observatory XMM-Newton have uncovered a thin-haze of ultra-hot gas between the galactic clusters Abell 222 and Abell 223, the first time they have seen the bridge of gas connecting the clusters of galaxies.
The European scientists say their findings help uncover some of the missing matter of the universe they had been expecting to find.
The observed gas is baryonic — that is, it interacts with light in some way and is made up of particles like protons or neutrons, which form the bulk of the atoms in other visible parts of the universe like galaxies, stars and gases.
Astronomers believe only five per cent of the matter forming the universe is baryonic, but even then they have only directly observed about half that amount. The European scientists said the gas they discovered represents probably the hottest and densest part of the diffuse gas they believe makes up half the missing baryonic matter.
The rest of the matter of the universe remains mysterious. About 20 per cent is believed to be made of dark matter, particles that don't interact with light but have been detected through their gravitational influence on distant galaxies, while another three-quarters is said to be made of dark energy, an even less understand phenomenon believed to be responsible for the accelerated expansion of the universe.
But the astronomers said their findings support the theory that dark matter forms a kind of invisible scaffolding for the structure of the universe, creating unseen gravitational centres that regular matter collects around. The discovery of the bridge of gas between the galactic clusters suggests something — possibly dark matter — is holding the two clusters together.
"So far we could only see the clusters, the dense knots of the web. Now we are starting to see the connecting wires of the immense cosmic spider web," said Max Planck Institute astrophysicist Aurora Simionescu, co-author of a paper presenting the findings in the May issue of Astronomy & Astrophysics Letters.
