Astronomers have found a gas cloud in the Universe that is the largest known to humanity. It is about 2 million light years across and reveals “cosmic web”.
Astronomers utilize the 10-m Keck I Telescope at the W. M. Keck Observatory in Hawaii and found the remote shining quasar UM 287 that shed light on the nearby gas cloud that is the largest known gas cloud, i.e. nebula, in the Universe. It is of about 460,000 parsecs (1.5 million light years) in length extending from UM 287’s host galaxy into intergalactic space connecting galaxies in a cosmic web.
“This is a very exceptional object: it’s huge, at least twice as large as any nebula detected before, and it extends well beyond the galactic environment of the quasar,” said first author Sebastiano Cantalupo, a postdoctoral fellow at UC Santa Cruz.
This study also presents the concept of the standard cosmological model of structure formation in the Universe, according to which galaxies are connected with each other in the form of web, i.e. “cosmic web”, of matter having dark matter in it. Computer simulations showed cosmic web of filaments in the Universe.
“This quasar is illuminating diffuse gas on scales well beyond any we’ve seen before, giving us the first picture of extended gas between galaxies. It provides a terrific insight into the overall structure of our universe,” stated coauthor J. Xavier Prochaska, professor of astronomy and astrophysics at UC Santa Cruz.
The hydrogen gas illuminated by the quasar emits ultraviolet light known as Lyman alpha radiation. The luminosity from the quasar is expanded by the growth of the Universe from an invisible ultraviolet wavelength to a visible light of violet color by the time it reaches the Keck Telescope after covering a distance of about 10 billion light-years. Calculation of distance helped astronomers to get wavelength for Lyman alpha radiation and building a special filter to take images at that wavelength.
“We have studied other quasars this way without detecting such extended gas. The light from the quasar is like a flashlight beam, and in this case we were lucky that the flashlight is pointing toward the nebula and making the gas glow,” Dr Cantalupo said.
“We think this is part of a filament that may be even more extended than this, but we only see the part of the filament that is illuminated by the beamed emission from the quasar.”
Distant quasar illuminates a filament of the cosmic web – University of California, Santa Cruz (http://goo.gl/GkMmoS)
Sebastiano Cantalupo et al. (2014). A cosmic web filament revealed in Lyman-α emission around a luminous high-redshift quasar Nature DOI: 10.1038/nature12898