New dwarf galaxies found near Milky Way

Our new celestial companions could help us understand how our Galaxy formed

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The Dark Energy Survey has now mapped one eighth of the sky over two of its five year run. Illustration: Dark Energy Survey Collaboration

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Eight new dwarf galaxies have been found around the Milky Way as part of the Dark Energy Survey (DES).

Seventeen dwarf satellites have been discovered around our Galaxy during the surveys first two years.

Dwarf galaxies are small collections of stars, with as few as 1,000 stars and are usually found in orbit around a larger galaxy.

It’s been predicted that these smaller galaxies clump together to form larger ones, and so studying them could be key to understanding how galaxies like our own grew to the size seen today.

Our new companions weren’t found during a dedicated search, however.

Instead the DES was taking snapshots of hundreds of millions of distant galaxies in a quest to understand the strange nature of dark energy, a mysterious force that is driving the Universe apart.

Occasionally these images captured a dwarf galaxy, and now a team of researchers is picking out them out from the data.

“Just this year, more than 20 of these dwarf satellite galaxy candidates have been spotted, with 17 of those found in Dark Energy Survey data,” says Alex Drlica-Wagner of the U.S. Department of Energy’s (DOE) Fermi National Accelerator Laboratory.

“We’ve nearly doubled the number of these objects we know about in just one year, which is remarkable.”

These newly found objects range from 80,000 to 700,000 light years away.

They are a million times less massive than the Milky Way, and only a billionth of the brightness, which is why they have been unobserved for so long.

The researchers were examining the southern half of the survey area, and many of the observations were made around the Milky Way’s two largest satellites, the Large and Small Magellenic Cloud.

“That result would be fascinating,” said Risa Wechsler of DOE’s SLAC National Accelerator Laboratory.

“Satellites of satellites are predicted by our models of dark matter.

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Either we are seeing these types of systems for the first time, or there is something we don’t understand about how these satellite galaxies are distributed in the sky.”