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This strange galaxy lets astronomers rethink a key theory



It's a real space curiosity.

Astronomers have discovered an ancient galaxy that seems to contain little or no dark matter – an invisible substance that astronomers used to think was an essential part of galaxy formation.

A billion-year-old galaxy, known as NGC 1052-DF2, is located 65 million light-years away in the Cetus constellation. It's the size of our Milky Way, but contains 400 times less dark matter than astronomers expected. The surprising discovery, described in an article published on March 28, in the journal Nature raises new questions about how galaxies are formed.

"You do not expect a galaxy to have dark matter. That's not something a galaxy can simply refuse." Pieter van Dokkum, professor of astronomy and physics at Yale University and head of the team of astronomers connecting the discovery with a pair of ground-based telescopes and the Hubble Space Telescope

The newly discovered galaxy also shines in its Center to have a black hole. This was another surprise, as astronomers have long believed that most galaxies contain black holes.

It is believed that dark matter accounts for about 27 percent of the universe, but because it does not emit light, it can not be directly observed. Instead, scientists concluded its existence based on its gravitational effects on galaxies and galaxy clusters.

It is widely believed that galaxies are formed when dark matter attracts gas that eventually fuses into stars ̵

1; and as soon as a galaxy forms, dark matter helps with it

Jeremiah Ostriker, an astrophysicist from Columbia University who was not involved in the study, said that this atypical galaxy could have been created by the collision of two typical galaxies and would leave behind a region without dark matter but with gas

Another possibility According to Ostriker, NGC 1052-DF2 contains a form of dark matter that is less massive than the "cold" dark matter that is thought to form typical galaxies.

Whatever According to an explanation by Ostriker, the discovery of the galaxy is a "killing blow" to the idea that dark matter could not exist.

The next challenge for researchers will be more examples of galaxies without dark matter. "It would be very exciting if there was more, or even if it is an ordinary galaxy," van Dokkum said. "So the hunt continues."

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