Dark Matter Clump Puzzles Astronomers

Using NASA’s Hubble Space Telescope, astronomers have identified what appears to be a large clump of dark matter in the Abell 520 galaxy cluster, which scientists believe is the remnants of a massive merger between galaxy clusters.

The clump of dark matter appears to have formed into a “dark core”, but galaxies surrounding the clump of dark matter aren’t behaving as expected. Rather than the dark core holding the galaxies together, recent data from Hubble suggests that the galaxies are parting ways.

The observation of the clump of dark matter was first made back in 2007, but it was dismissed by the scientific community as bad data. Upon taking a second look recently at the Abell 520 galaxy cluster, however, scientists uncovered evidence that the collection of dark matter is, in fact, not behaving as expected.

“This result is a puzzle,” said astronomer James Jee. “Dark matter is not behaving as predicted, and it’s not obviously clear what is going on. Theories of galaxy formation and dark matter must explain what we are seeing.”

The study, published in the Astrophysical Journal, raises more questions than answers, and challenges conventional theories about the formation of galaxies and the dark matter that holds them together.

“We were not expecting this,” the study team’s senior theorist, Arif Babul of the University of Victoria, said in a news release. “According to our current theory, galaxies and dark matter are expected to stay together, even through a collision. But that’s not what’s happening in Abell 520. Here, the dark matter appears to have pooled to form the dark core, but most of the associated galaxies seem to have moved on.”