Published: Fri, March 30, 2018
Science | By Dan Gutierrez

A Victory for Dark Matter in a Galaxy Without Any

A Victory for Dark Matter in a Galaxy Without Any

The galaxy NGC 1052-DF2, or DF2 for short, reportedly has 400 times less dark matter than expected for an object of its size.

Astronomers have discovered a odd galaxy that is missing most, if not all, of its dark matter.

Dark matter is an invisible and mysterious substance that is thought to be crucial to the formation of galaxies.

Although it has never been directly observed, scientists are confident that this elusive material exists because of the gravitational effects it appears to have on astronomical objects.

A team from the Connecticut-based university used the Hubble Space Telescope to closely observe the galaxy, measuring its distance from Earth and looking at the star clusters within.

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"I spent an hour just staring at this image", lead researcher Pieter van Dokkum of Yale University says as he recalls first seeing the Hubble image of NGC 1052-DF2. "It's so rare, particularly these days after so many years of Hubble, that you get an image of something and say, 'I've never seen that before.' This thing is astonishing, a enormous blob that you can look through". Instead, van Dokkum's team found those star clusters moving languidly around NGC 1052-DF2, a sign that there may well be very little or no dark matter within that galaxy at all.

Since dark matter was (sort of) discovered, researchers assumed dark matter was essential to galaxy formation. And it was also mostly transparent, with other galaxies visible behind it. In spite of the fact that we can't straightforwardly watch it, we know dark matter is there in light of the fact that we can perceive how its gravity influences ordinary matter. "There is no theory that predicts these types of galaxies - how you actually go about forming one of these things is completely unknown", Merritt said. "But what would you get if there were no dark matter at all?" The discovery of NGC 1052-DF2 demonstrates that dark matter is somehow separable from galaxies. So even among this unusual class of galaxy, NGC 1052-DF2 is an oddball. It wasn't long after that they realized it was missing one of the things that, according to all prior research, makes galaxies tick: dark matter.

Dark matter, it seems, might be spread out across the universe more unevenly than scientists had thought, van Dokkum explained. That brought about an approximated mass that was incredibly reduced for a galaxy- like 108 solar masses. He points out that the galaxy, memorably named NGC1052-DF2, is orbiting another one. The galaxy is a complete mystery, as everything about it is unusual. Simply put, the velocity at which clusters orbit a galaxy is related to the amount of matter-normal or dark-that a galaxy contains.

Another idea is that gas moving toward the giant elliptical NGC 1052 may have fragmented and formed NGC 1052-DF2. This study was published in Nature. For example, they can look at how fast stars cruise around a galaxy. But when the team compared them to a better image from the Sloan Digital Sky Survey, they found a surprising mismatch. Given that there isn't a trace of the dark matter, data suggests that it's made entirely of normal matter.

"Paradoxically, the presence of NGC1052- DF2 might misstate options to dark issue", the writers end, keeping in mind that those choices consist of both variants of MOND and also emergent gravity. Future observatories under construction, such as the European Extremely Large Telescope in Chile's Atacama Desert, or NASA's James Webb Space Telescope, should be able to take such measurements.

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