Dwarf 'Satellite Galaxy' Detected 10 Billion Light Years Away
January 18, 2012

Dwarf ‘Satellite Galaxy’ Detected 10 Billion Light Years Away

An astronomer has discovered a faint "satellite galaxy" that is the lowest-mass object ever detected 10 billion light years away.

Finding this dwarf galaxy at such a long distance away may be able to help astronomers find similar objects and confirm or reject theories about the structure of the universe.

University of California physics professor Chris Fassnacht said in a statement that theory predicts that galaxies should be surrounded by halos of smaller, satellite blobs of mass.

Although astronomers have detected these satellites around our own galaxy, they had not previously detected the predicted satellites of more distant galaxies.

Fassnacht and colleagues looked for faint or dark satellites of distant galaxies using a method called gravitational lensing.  They used the Keck II telescope at the W.M. Keck Observatory on Mauna Kea, Hawaii and found two galaxies aligned with each other.

The nearer object's gravitational field deflects the light from the more distant object as the light passes through or near the other object's gravitational field, which creates a distorted image as if passed through a lens.

The researchers said that by analyzing these distorted images, they could determine if there were any satellite galaxies clustered around the "lens" galaxy.

The Keck telescopes are able to achieve a higher resolution than the Hubble Space Telescope because its adaptive optics make adjustments to compensate for the effects of the Earth's atmosphere.

Fassnacht said the technique can be applied to many more galaxies.

“As we collect more objects, we can do more precise tests of our simulations and make predictions about the structure of the universe,” he said in a statement.

“Now we have one dark satellite, but suppose that we don´t find enough of them – then we will have to change the properties of dark matter," Simona Vegetti, a postdoctoral researcher at the Massachusetts Institute of Technology and first author of the study published in the journal Nature, said in a statement. “Or, we might find as many satellites as we see in the simulations, and that will tell us that dark matter has the properties we think it has.”


Image Caption: The gravitational lens B1938+666 as seen in the infrared when observed with the 10-meter Keck II telescope with Adaptive Optics on Mauna Kea, Hawaii. In the center is a massive red galaxy 9.8 billion light-years from Earth that acts like a cosmic magnifying glass, distorting the light from an even more distant galaxy, 17.3 billion light-years away. The result is a spectacular Einstein ring image of the background galaxy. The team used distortions within the ring to find evidence for a low-mass dark galaxy, which is a satellite of the foreground lensing galaxy. Using this gravitational lensing effect the mass of the dark galaxy was found to be 200 million times the mass of the Sun, which is similar to the masses of the satellite galaxies found around our own Milky Way, but is 9.8 billion light-years further away. Credit: D. Lagattuta / W. M. Keck Observatory


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