Suzaku Catches First Glimpse of Galaxy Cluster

The Suzaku X-ray observation satellite is a joint venture between NASA and the Japanese space agency JAXA, and its primary purpose is to investigate high-energy astronomical phenomena, such as black holes and supernovae. Just recently, it managed to snap its first images of a galaxy cluster, in a portion of the sky several million light-years across. The X-ray radiation its sensitive instruments picked up came from cosmic gas gathered at the outskirts of the formation, its operators announced.

“These Suzaku observations are exciting because we can finally see how these structures, the largest bound objects in the universe, grow even more massive,” University of California in Berkeley (UCB) expert Matt George explained. He has also been the lead author of a new paper detailing the observations, published in the May 11th issue of Monthly Notices of the Royal Astronomical Society.

Between May 11th and 14ht, 2007, the spacecraft snapped five pictures of the PKS 0745-191 galactic cluster, which is located about 1.3 billion light-years away, in the Constellation Puppis. The main target of its instruments was the hot cosmic gas that permeated the entire formation, heated to about a million degrees Celsius. The primary scientific tools aboard the spacecraft are the X-ray Telescope (XRT), the X-ray Spectrometer (XRS), the X-ray Imaging Spectrometer (XIS), and the Hard X-ray Detector.

Astronomers had expected to see a relative state of equilibrium inside the gas, in that, usually, the most dense and hot part of it falls towards the center of the cluster, while, at the outskirts, only mildly hot gas remains. Temperatures and pressures affecting it gradually drop the farther away from the core the gas is. However, in this particular cluster, the gas was not arranged in an orderly fashion, and astrophysicists believe this is happening because matter continues to fall inside the massive formation.

“Clusters are the most massive, relaxed objects in the universe, and they are continuing to form now,” Cambridge Institute of Astronomy team member Andy Fabian shared. He added that the distance from the core where the gas lost its orderly state and entered its chaotic one was called a cluster's “virial radius.” The reason why Suzaku's observations are so important is the fact that it pictured the cluster's formation process beyond the virial radius for the first time ever. “It gives us the first complete X-ray view of a cluster of galaxies,” Fabian said.

“With more Suzaku observations in the outskirts of other galaxy clusters, we'll get a better picture of how these massive structures evolve,” George concluded. The satellite was developed by the Japanese Institute of Space and Astronautical Science (ISAS), NASA, and a consortium of US and Japanese institutions. It was launched on July 10th, 2005, after the first attempt, in 2000, failed, and the satellite was lost.