New dwarf galaxies discovered in orbit around Milky Way

Scientists have found nine new dwarf satellites orbiting the Milky Way, the largest number ever discovered at once.
According to the University of Cambridge astronomers, three of the discovered objects are definite dwarf galaxies - small celestial objects that orbit larger galaxies.
The others could be either dwarf galaxies or globular clusters - objects with similar visible properties to dwarf galaxies, but not held together with dark matter.
The finding could hold the key to understanding dark matter, the mysterious substance which holds our galaxy together, researchers said.
The new results mark the first discovery of dwarf galaxies in a decade, after dozens were found in 2005 and 2006 in the skies above the northern hemisphere.

The new satellites were found 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 newly discovered objects 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.
"The discovery of so many satellites in such a small area of the sky was completely unexpected. I could not believe my eyes," said Dr Sergey Koposov of Cambridge's Institute of Astronomy, the study's lead author.

Dwarf galaxies are the smallest galaxy structures observed, the faintest of which contain just 5,000 stars - the Milky Way, in contrast, contains hundreds of billions of stars.
Standard cosmological models of the universe predict the existence of hundreds of dwarf galaxies in orbit around the Milky Way, but their dimness and small size makes them incredibly difficult to find, even in our own 'backyard'.
Since they contain up to 99 per cent dark matter and just one per cent observable matter, dwarf galaxies are ideal for testing whether existing dark matter models are correct.
The Cambridge team used the publicly available data taken during the first year of the Dark Energy Survey to carry out their analysis.

The Dark Energy Survey, headquartered at the US Department of Energy's Fermi National Accelerator Laboratory, is a five-year effort to photograph a large portion of the southern sky in unprecedented detail.
The research will be published in The Astrophysical Journal.