Scientists at the University of Cambridge have discovered nine new dwarf galaxies orbiting the Milky Way. It is the largest number of dwarf satellites ever discovered at once, and also marks the first discovery of dwarf galaxies in a decade. Findings may help astronomers unravel the mystery behind dark matter. Dark matter accounts for more than 85% of the universe’s total mass, but it is invisible. Dark matter makes its presence known only through the gravitational effect.
A ‘completely unexpected’ discovery
Dwarf galaxies are small celestial objects that orbit larger galaxies. The newly discovered objects are a million times less massive and a billion times dimmer than Milky Way. The closest of them is just 95,000 light years away, while the farthest is over a million light years away. All the nine candidates are found in the southern hemisphere near the Large and Small Magellanic Cloud.
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Sergey Koposov, the lead author of the study, said the discovery of so many small galaxies in such a small area was “completely unexpected.” Findings of the study were published in the latest issue of The Astrophysical Journal. Standard scientific models predict that there could be hundreds of dwarf galaxies orbiting the Milky Way. But their small size and dimness makes it extremely difficult to find.
Dwarf galaxies contain up to 99% dark matter
Vasily Belokurov, one of the co-authors of the study, said dwarf galaxies were the “final frontier” to test the theories of dark matter. Dwarf galaxies contain up to 99% dark matter and only 1% visible matter. So, they are ideal for testing whether existing models of dark matter are correct. One of the theories states that the dark matter might consist of particles that annihilate each other and emit gamma rays.
Findings of the University of Cambridge were released alongside results of a separate study by scientists with the Dark Energy Survey. To carry out their analysis, both groups used publicly available data obtained during the first year of the Dark Energy Survey.