German Researchers Discover Galaxy Cluster | Germany| News and in-depth reporting from Berlin and beyond | DW | 05.03.2005
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German Researchers Discover Galaxy Cluster

Scientists will have to alter their theories about the Big Bang --German astronomers have discovered a cluster of galaxies that suggests the universe evolved into its present form far sooner than was thought.

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The oldest galaxy cluster yet discovered: XMMU J2235.3-2557

The search for new galaxies must be a tedious and often thankless task for astronomers. But when scientists from the Max Planck Institute for Astrophysics in Garching, Germany decided to direct the orbiting satellite XMM-Newton into the vast expanses of a nearby galaxy, they were surprised at what they found -- a dense formation of galaxies some nine billion light years away.

The surprise is that with current estimates, the universe is about 13.7 billion years old. The discovered cluster of galaxies, catchily named XMMU J.2235.3-2557, was formed when the universe was just a mere five billion years old. This comes much earlier than researchers previously believed. The European Space Agency (ESA) and NASA declared the sphere-like cluster of galaxies to be "the most distant massive structure yet detected in the universe."

"We have underestimated how quickly the early universe matured into its present-day incarnation," said Piero Rosati, an astronomer at the European Southern Observatory (ESO), based in Garching. "The universe has grown up fast."

ESO orbiter made discovery possible

Galaxienhaufen XMMU J2235.3-2557 ESO

Light from the cluster travelled over 9 billion light years before XXM-Newton took in the rays

Until now, the earliest evidence for the timetable of galactic development has come from "proto-clusters" -- galactic clusters in the making -- that have been dated by analysis of their light to be up to 10 billion years old. But it was not possible to determine just how quickly these youthful galactic structures took to be mature galaxies as we know them today.

"We are quite surprised to see that exquisite structures like this could exist at such early epochs," said Christopher Mullis, an astronomer from the University of Michigan who participated in the discovery. He compared it to a kingdom popping up out of nowhere.

The discovery was made possible by trawling through the data retrieved by ESO's orbiter XMM-Newton. In the data, radiation was detected from the X-ray part of the energy spectrum which is invisible to optical telescopes.

The ESO scientists then pointed the Very Large Telescope (VLT) in Chile's Atacama Desert at the discovery and found optical evidence to support the X-ray emissions.

The observations showed that the galaxies in the cluster are not chaotic and spread out randomly, but smoothly elliptical. That indicates gravitational forces at work in the cluster. In addition, the galaxies are filled with stars emitting light in the red part of the spectrum. This is an unmistakable sign of stellar antiquity.

Galaxy cluster XMMU J.2235.3-2557 possesses hundreds or possibly thousands of galaxies that are bound to each other through invisible tendrils of gravitational force. By comparison, our own Milky Way galaxy is a relatively "low-density" region of the universe.

For astronomers at the Max Planck Institute for Astrophysics in Garching, the search for further clusters continues. It is a matter of hit and miss sometimes, but both ESA and NASA said that the discovery of XMMU J.2235.3-2557 "might just be the tip of the iceberg."

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