Astronomers from the Astrophysikalisches Institut in Potsdam, Germany, discovered the most luminous X-ray cluster ever to be detected at a distance of nearly 8 billion light years away from Earth. Only a handful of galaxy clusters are believed to exist at this distance, making the discovery exceptional. In terms of astronomical theories, this discovery serves as another confirmation of the existence of dark energy, a mysterious component allegedly causing the Universe’s expansion to accelerate.
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Galaxy clusters play a key role in understanding cosmological processes. Therefore, there are many galaxy surveys aimed at mapping the various galaxies and clusters and studying their properties. Distant clusters are harder to locate, and distant X-ray luminous clusters are quite rare. Large area surveys are needed in order to detect these clusters.
The X-ray Multi-Mirror Mission (XMM-Newton), launched in 1999 by the European Space Agency, is the largest medium sensitivity X-ray survey to date. While busy studying a particular object, the XMM-Newton happened upon another object, which was placed in a catalog for future follow up under the number 2XMM J083026+524133.
While performing systematic analysis of objects in the survey’s catalog, Georg Lamer of the Astrophysikalisches Institut Potsdam, Germany together with a team of astronomers noticed this object, which stood out due to its brightness. They turned to the Sloan Digital Sky Survey (SDSS), a galaxy survey that began in 1998 and is still underway, but found no galaxy in this object’s direction. The scientists then used the Large Binocular Telescope in Arizona to take a deep exposure picture of the object.
The picture revealed a galaxy cluster, estimated to be 7.7 billion light years away from Earth. The cluster is estimated to contain as much mass as a thousand large galaxies, a large amount of it in the form of hot gas.
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“Such massive galaxy clusters are thought to be rare objects in the distant Universe. They can be used to test cosmological theories,” said Georg Lamer. In fact, the mere existence of this cluster confirms the existence of dark energy, a mysterious form of matter accounting for 75% of the matter in the universe, and causing the acceleration of the Universe’s expansion.
This acceleration hinders the development of massive clusters in recent times. Therefore, any such clusters must have formed in the earlier Universe. “The existence of the cluster can only be explained with dark energy,” Lamer commented.
The XMM-Newton covers about 1% of the entire sky. Subsequently, chances of finding another massive cluster with this survey are very low. The eROSITA, the extended Roentgen Survey with an Imaging Telescope Array that will be launched after 2009 by the Max Planck Institute, should perform the first imaging all-sky survey in the medium energy X-ray range. This survey, along with others that are underway, should be able to detect more of these massive clusters in the near future.
TFOT reported on NASA’s creation of an ultraviolet mosaic of the Triangulum Galaxy, a galaxy in the Local Group, the galaxy cluster in which the Milky Way resides. In another story, TFOT covered NASA’s approval for the construction of the High-Resolution Soft X-Ray Spectrometer (SXS), an instrument devised to study the extreme environments of the universe. The new instrument will help researchers explore dark matter on a large scale as well as the evolution of large galactic structures.
Further information on the new X-ray cluster discovery can be found on the Arxiv website (PDF) and in the ESA press release.
