Miércoles 3 de Septiembre de 2008, Ip nº 245

Dark energy and a monster galactic cluster
París: An orbiting telescope has spotted a massive cluster of galaxies in deep space that helps to confirm theories about dark energy.

Detected in a scan by the European Space Agency's (ESA) orbiting X-ray telescope, XMM-Newton, the cluster's mass is about 1,000 times that of our own galaxy, the Milky Way. The huge cluster (known by its catalogue number of 2XMM J083026+524133) lies 7.7 billion light-years from Earth, the ESA said on Monday.

Primordial cluster

Current theory holds that, most of the universe comprises dark energy, an enigmatic force that is causing the expansion of the cosmos to accelerate. The outward drive of dark energy is thought to be such that, in more recent times, massive clusters of galaxies have lacked the gravitational glue to hold together.

Therefore the newly discovered super-cluster can only have been formed earlier in the history of the Universe, said the experts, a notion that is backed by its huge distance from Earth.

"The galaxy cluster is so big that there can only be a handful of them at that distance," said an ESA statement, likening the achievement to finding a "cosmic needle in a haystack."

The observation was made by a team led by Georg Lamer of the Potsdam Astrophysics Institute, in Germany, initially using a photon-imaging camera aboard the XMM-Newton.

Scorching gases

Intrigued by the indicators of scorching gases spewed out by X-ray sources, the astronomers followed up by getting a deep exposure image of the region from a large binocular telescope in the USA's Arizona desert.

Dark energy is believed to comprise more than 72 per cent of the detected Universe and dark matter – heavy particles still not proven to exist – accounts for around 23 per cent, according to cosmological theory. That leaves less than five per cent of normal, or baryonic, matter, the category for the protons and neutrons that compose it.


  26/08/2008. Cosmos Magazine.