Scientists discover most distant galaxy cluster | Science| In-depth reporting on science and technology | DW | 09.03.2011
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Scientists discover most distant galaxy cluster

Astronomers locate a rare galaxy cluster that formed only 3 billion years after Big Bang. The discovery could change current theories about the ways galaxies and galaxy clusters form.

Image composite of very long exposures taken with ESO's Very Large Telescope in Chile and the NAOJ’s Subaru telescope on Hawaii. Most of the visible objects are very faint and distant galaxies. The clump of faint red objects to the right of center is the most remote mature cluster of galaxies yet found

The cluster's characteristics surprised astronomers

Astronomers discovered the most mature distant galaxy cluster ever known, at a distance of roughly 10 billion light years from Earth. Galaxy clusters are the largest cosmological entities known, comprising very large groups of galaxies held together by gravity.

"It is the oldest and most distant that we've found," Raphael Gobat, a researcher with France's Laboratoire AIM-Paris-Saclay, told Deutsche Welle.

The research team used equipment at the European Southern Observatory in Chile as well as other telescopes to measure distances of "very faint objects" first detected by the NASA Spitzer space telescope, and confirmed the existence of this new galaxy cluster, known as CL J1449+0856.

Galactic formation theories

However, not only was this rare galaxy cluster detected, but scientists were surprised to find that it was a "mature system," meaning the galaxy was no longer giving birth to new stars as astronomers would have expected of young galaxies. Galaxy clusters are thought to expand over time making such massive clusters rare in the early universe.

The ESO in Chile

The Very Large Telescope at the ESO played a role in finding the galaxy cluster

Images from the newly found galaxy cluster show it as it was when the universe was about 3 billion years old - less than one quarter of its current age - and may force scientists to rethink existing cosmological formation theories, Gobat said.

"It tells you that at this epoch, you had the co-existence of structures that were massive but there was at least one mature galaxy cluster, and you had actively massive star-forming proto-clusters," he said. "If someone finds more of these, it will tell us something about the growth of such structures."

Other scientists who were not part of the study said the results were intriguing, and that they looked forward to future work on this new cluster.

"This is very interesting stuff, and is clearly showing that we don't yet know everything about galaxy and galaxy cluster formation," David Clements, a physics lecturer at Imperial College London, wrote in an e-mail to Deutsche Welle. "It provides some interesting new insights to cluster and elliptical galaxy formation, pushing these back, for at least some objects, to earlier stages than we might have expected."

The research team, comprised of scientists from Europe, Japan and the United States, published their scientific paper detailing these results in the February edition of the journal Astronomy & Astrophysics.

Author: Cyrus Farivar

Editor: Sean Sinico

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