Article Posted on : - Aug 26, 2008

PARIS (BNS): The European Space Agency’s orbiting X-ray observatory XMM-Newton has discovered a Galactic monster, estimated to contain as much mass as a thousand large galaxies. It is the most massive cluster of galaxies called 2XMM J083026+524133, seen in the distant Universe until now. The galaxy cluster is so big that there can only be a handful of them at that distance, making this a rare catch indeed. The discovery confirms the existence of dark energy.

The newly-discovered monster, 2XMM J083026+524133, is estimated to contain as much mass as a thousand large galaxies. Much of it is in the form of 100-million-degree hot gas. It was first observed by chance as XMM-Newton was studying another celestial object and 2XMM J083026+524133 was placed in a catalogue for a future follow-up.

Georg Lamer, Astrophysikalisches Institut Potsdam, Germany, and a team of astronomers discovered the record-breaking cluster as they were performing a systematic analysis of the catalogue. Based on 3,500 observations performed with XMM-Newton's European Photon Imaging Camera (EPIC) covering about one per cent of the entire sky, the catalogue contains more than 1,90,000 individual X-ray sources. The team was looking for extended patches of X-rays that could either be nearby galaxies or distant clusters of galaxies.

The scientists said that the very presence of this cluster confirms the existence of a mysterious component of the Universe called dark energy.

This discovery has been likened to finding a cosmic 'needle in a haystack'. It is believed that J083026+524133 stood out because it was so bright. While checking visual images from the Sloan Digital Sky Survey, the team could not find any obvious nearby galaxy in that location. So they turned to the Large Binocular Telescope in Arizona and took a deep exposure.

Using the XMM-Newton data scientists found cluster of galaxies, at a distance of 7.7 thousand million light-years. XMM-Newton is sensitive enough to routinely find galaxy clusters at this distance. What surprises is that the cluster contains thousand times the mass of our own galaxy, the Milky Way.

Explaining about the massive galaxies, Lamer said, "Such massive galaxy clusters are thought to be rare objects in the distant Universe. They can be used to test cosmological theories." Indeed, the very presence of this cluster confirms the existence of a mysterious component of the Universe called dark energy. No one knows what dark energy is, but it is causing the expansion of the Universe to accelerate. This hampers the growth of massive galaxy clusters in more recent times, indicating that they must have formed earlier in the Universe."

“The existence of the cluster can only be explained with dark energy," says Lamer.

Yet he does not expect to find more of them in the XMM-Newton catalogue. "According to the current cosmological theories, we should only expect to find this one cluster in the one per cent of the sky that we have searched," says Lamer.