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Milky Way Gains Nine New Galaxy Neighbors

Mar 10, 2015 04:45 PM EDT
dwarf satellite galaxies
Pictured: The Magellanic Clouds and the Auxiliary Telescopes at the Paranal Observatory in the Atacama Desert in Chile. Only 6 of the 9 newly discovered satellites are present in this image.
(Photo : V. Belokurov, S. Koposov (IoA, Cambridge))

Our own Milky Way has recently gained nine new neighbors - rare dwarf satellite galaxies, which could help astronomers better understand the mysterious dark matter that holds our galaxy together, new research says.

Dwarf galaxies are small celestial objects that orbit larger galaxies, and this recent treasure trove is not only the largest number discovered at once, but is also the first time in the last decade that these satellites have been found. The last time was in 2005 and 2006 when dozens were identified in the skies above the Northern Hemisphere.

This latest batch is located in the Southern Hemisphere near the Large and Small Magellanic Cloud, the largest and most well-known dwarf galaxies in the Milky Way's orbit.

"The discovery of so many satellites in such a small area of the sky was completely unexpected," lead author Dr. Sergey Koposov from the University of Cambridge said in a statement. "I could not believe my eyes."

That's because dwarf galaxies are so dim and so small it makes them nearly impossible to find, despite the fact that common theory suggests there are hundreds of them orbiting in our own backyard. The newly discovered objects, for example, are a billion times dimmer than the Milky Way, and a million times less massive. The closest is about 95,000 light years away, while the most distant is more than a million light years away.

According to the Cambridge team, three of the discovered objects are definitely dwarf galaxies, while others could be either dwarf galaxies or globular clusters - similar objects that are not held together by dark matter.

Dark matter makes up 25 percent of all matter and energy in the Universe, but the fact that it's invisible makes it difficult to study - this new discovery could help change that.

"Dwarf satellites are the final frontier for testing our theories of dark matter," added co-author Dr. Vasily Belokurov. "We need to find them to determine whether our cosmological picture makes sense."

The findings were published in The Astrophysical Journal.

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