Astronomers Discover a Rare Galaxy Without Any Dark Matter

Saturday, March 31, 2018 - 12:35

Astronomers have discovered the first and only known galaxy without dark matter, the invisible and mysterious substance making up more than a quarter of the universe.

The discovery of DF2 was made with a new kind of telescope developed by Roberto Abraham, an astronomer at the University of Toronto, and Pieter van Dokkum of Yale University, Aljazeera reports.

Van Dokkum and his team spotted the galaxy with the Dragonfly Telephoto Array, a custom-built telescope in New Mexico they designed to find ultra-diffuse galaxies.

These faint galaxies, which include the newly discovered DF2, can be as large as the Milky Way but shine only one percent as brightly. "For a galaxy this size, it should have 30 times as much dark matter as regular matter," he told AFP news agency on Wednesday. "What we found is that there is no dark matter at all."

It’s not the first time that someone has claimed to have found a galaxy short in dark matter. But up until now, practically every other galaxy we’ve spotted in the Universe has had some kind of dark matter signature. In fact, dark matter is thought to be the most abundant material inside galaxies. But this new one, detailed in Nature, has 400 times less dark matter than researchers expected to find, based on the galaxy’s size and volume. The galaxy is made up of just the mass of the star clusters inside it. There’s either a very tiny amount of dark matter — or none at all.

Scientists have a few ideas about what dark matter might be, though nothing is certain. It could be regular matter that we just can’t see, such as neutron stars — the faint leftovers of dead suns. Or it could be brown dwarfs, the huge planet-like objects that aren’t big enough to become full-fledged stars. The problem is these objects aren’t super abundant and can’t explain all the dark matter we suspect exists. Instead, others have proposed the idea the dark matter is made up of minuscule particles we just haven’t discovered yet.

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