Another possibility is that the core contained many galaxies

Astronomers using data from NASA’s burberry ties Hubble Telescope have observed what appears to be a clump of dark matter left behind from a wreck between massive clusters of galaxies. The result could challenge current theories about dark matter that predict galaxies should be anchored to the invisible substance even during the shock of a collision. Abell 520 is a gigantic merger of galaxy clusters located 2.4 billion light-years away. Dark matter is not visible, although its presence and distribution is found indirectly through its effects. Dark matter can act like a magnifying glass, bending and distorting light from galaxies and clusters behind it. Astronomers can use this effect, called gravitational lensing, to infer the presence of dark matter in massive galaxy clusters. This technique revealed the dark matter in Abell 520 had collected into a “dark core,” containing far fewer galaxies than would be expected if the dark matter and galaxies were anchored together. Most of burberry watches the galaxies apparently have sailed far away from the collision. “This result is a puzzle,” said astronomer James Jee of the University of California in Davis, lead author of paper about the results available online in The Astrophysical Journal. “Dark matter is not behaving as predicted, and it’s not obviously clear what is going on. It is difficult to explain this Hubble observation with the current theories of galaxy formation and dark matter.” Initial detections of dark matter in the cluster, made in 2007, were so unusual that astronomers shrugged them off as unreal, because of poor data. New results from NASA’s Hubble Space Telescope confirm that dark matter and galaxies separated in Abell 520. “Observations like those of Abell 520 are humbling in the sense that in spite of all the leaps and bounds in our understanding, every now and then, we are stopped cold,” said Arif Babul of the University of Victoria, British Columbia. One way to study the overall properties of dark matter is by analyzing collisions between galaxy clusters, the largest structures in the universe. When galaxy clusters crash, astronomers expect galaxies burberry sunglasses to tag along with the dark matter, like a dog on a leash. Clouds of hot, X-ray emitting intergalactic gas, however, plow into one another, slow down, and lag behind the impact. That theory was supported by visible-light and X-ray observations of a colossal collision between two galaxy clusters called the Bullet Cluster. The galactic grouping has become an example of how dark matter should behave. Studies of Abell 520 showed that dark matter’s behavior may not be so simple. Using the original observations, astronomers found the system’s core was rich in dark matter and hot gas, but contained no luminous galaxies, which normally would be seen in the same location as the burberry scarves dark matter. NASA’s Chandra X-ray Observatory was used to detect the hot gas. Astronomers then used the Canada-France-Hawaii Telescope and Subaru Telescope atop Mauna Kea to infer the location of dark matter by measuring the gravitationally lensed light from more distant background galaxies. The astronomers then turned to the Hubble’s Wide Field Planetary Camera 2, which can detect subtle distortions in the images of background galaxies and use this information to map dark matter. To astronomers’ surprise, the Hubble observations helped confirm the 2007 findings. “We know of maybe six examples of high-speed galaxy cluster collisions where the dark matter has been mapped,” said the team of scientists. One possible explanation for the discrepancy is that Abell 520 has resulted from a more complicated interaction than the Bullet Cluster encounter. The massive galaxy may have formed from a collision between three galaxy clusters, instead of just two colliding systems in the case of the Bullet Cluster. Another possibility is that the core contained many galaxies, but they were too dim to be seen, even by Hubble. Those galaxies would have to have formed dramatically fewer stars than other normal galaxies.Cheap burberry - designer bags, shoes, accessories, clothing outlet 2012. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. You may also interested in: Burberry Bags burberry outlet online cheap burberry outlet online Burberry Bags, Burberry Outlet Online at Huge Savings. Information from www.primemall.com.