Nine dwarf galaxies found orbiting the Milky Way

Astronomers from the University of Cambridge have discovered nine dwarf satellites orbiting the Milky Way, the largest number ever discovered at once.

The findings may help unravel the mysteries behind dark matter, the invisible substance holding galaxies together.

The results also mark the first discovery of dwarf galaxies - small celestial objects that orbit larger galaxies - in a decade.

The 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," said Sergey Koposov from the Cambridge University's Institute of Astronomy and the study's lead author.

According to the team, three of the discovered objects are definite dwarf galaxies while the others could be either dwarf galaxies or globular clusters - objects with visible properties similar to dwarf galaxies but not held together with dark matter.

The 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.

"Dwarf satellites are the final frontier for testing our theories of dark matter," added Vasily Belokurov, one of the study's co-authors.

Since they contain up to 99 percent dark matter and just one percent observable matter, dwarf galaxies are ideal for testing whether existing dark matter models are correct.

Dark matter - which makes up 25 percent of all matter and energy in our universe - is invisible, and only makes its presence known through its gravitational pull.

The Cambridge findings were released with the results of a separate survey by astronomers with the Dark Energy Survey, headquartered at the US Department of Energy's Fermi National Accelerator Laboratory.

Both teams used the publicly available data extracted during the first year of the Dark Energy Survey to carry out their analysis.