In Brief

Galaxy without dark matter challenges scientific theories

NGC1052-DF2 appears to be lacking the mysterious substance

Scientists are baffled after discovering the existence of an “unusually transparent” galaxy that appears to contain no dark matter.

The “ghost” galaxy, known as NGC1052-DF2, is some 65 million light-years away and about the size of the Milky Way. And according to a new study published in the journal Nature, it contains no more than 1/400th of the amount of dark matter that astronomers had expected.

“The absence of dark matter from a small patch of sky might appear to be a non-problem, given that astronomers have never directly observed dark matter anywhere,” says The Guardian.

However, the newspaper continues, most current theories of the physics of the universe suggest that where regular matter is found, dark matter must also be present, with the latter dominating at a ratio of 5:1.

As it has greater mass than normal matter, dark matter is believed to be vital in holding the necessary gas together while galaxies are forming, explains the BBC

“In other words, no dark matter, no galaxy,” says National Geographic.

The discovery of an apparent exception to that rule, NGC1052-DF2, therefore poses major questions about our understanding of the universe.

“Finding a galaxy without dark matter is unexpected, because this invisible, mysterious substance is the most dominant aspect of any galaxy,” said lead study author Pieter van Dokkum, from Yale University. “Something like this has never been seen. NGC1052-DF2 challenges the standard ideas of how we think galaxies form.”

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.

“I spent an hour just staring at the Hubble image," said van Dokkum, the Nasa website reports. “It’s so rare, particularly these days after so many years of Hubble, that you get an image of something and you say, ‘I’ve never seen that before.’

“This thing is astonishing: a gigantic blob that you can look through. It’s so sparse that you see all of the galaxies behind it. It is literally a see-through galaxy.”

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