NASA shows 'oddball' galaxy that lacks dark matter; jokes it needs 'galactic-grade glue’

Galaxies tend to exist in humungous groups, sometimes these bustling clusters of hundreds of thousands of galaxies outweigh the Sun. But what holds the galaxies together in the Universe? Certainly not the gravitational force. On Wednesday, NASA revealed that most galaxies rotate so tremendously fast that the gravity generated by gas and stars alone “is not enough to keep them together.” These massive galactic clusters are, in fact, held by the mysterious invisible substance called the Dark Matter. The dark matter that makes up most of the universe, holds the entire universe together. 

Interestingly, NASA on June 23 shared the ‘unique’ imagery of an unusual "see-through" galaxy sitting almost “as wide as the Milky Way galaxy” and about 72 million light-years away that actually lacks this invisible Dark Matter. This galaxy has the potential to “upset” theories of galaxy formation and evolution. “Astronomers found that this ghostly galaxy doesn’t appear to have a central region, spiral arms, or a disk – and contains about 1/400 of the amount of dark matter expected by astronomers,” NASA revealed in a post.

It added, that this “oddball galaxy” contains only 1/200 of the number of stars as compared to the Milky Way. It has no discernible dark matter or enough stars that account for most of the galaxy’s gravity. NASA, therefore ironically stated, “Glue – but make it galactic-grade.” 

Separately in a blog, NASA explained that the oddball galaxy was uncovered by Hubble Space Telescope. And since spotted, it had flabbergasted the astronomer as it didn't have much dark matter. “Some thought the finding was hard to believe and looked for a simpler explanation,” said the space agency. “Dark matter, after all, is the invisible glue that makes up the bulk of the universe's matter. All galaxies appear to be dominated by it; in fact, galaxies are thought to form inside immense halos of dark matter,” it continued.

[Ultra-diffuse galaxy NGC 1052-DF2, or DF2. Credit: NASA]

The original finding of this “oddball galaxy” or the NGC 1052-DF2 which the scientists also refer to it simply as “DF2” was published in 2018 here on Hubblesite. 

"We went out on a limb with our initial Hubble observations of this galaxy in 2018," Pieter van Dokkum of Yale University in New Haven said in a NASA release. "I think people were right to question it because it's such an unusual result. It would be nice if there were a simple explanation, like a wrong distance. But I think it's more fun and more interesting if it actually is a weird galaxy,’ he added. 

Scientist try to decode the 'mystery'

NASA's team of scientists has been trying to determine if the amount of the galaxy's dark matter is directly proportional to how far away it is from Earth. If DF2 is as far from Earth, as van Dokkum's team asserts, the galaxy's dark-matter content may only be a few percent, NASA says in an analysis. The team's conclusion is based on the motions of the stars within the galaxy; their velocities are influenced by the pull of gravity. But if DF2 were closer to Earth, as some astronomers claim, it would be intrinsically fainter and less massive, in which case the galaxy would need dark matter. 

In another interesting take, team member Zili Shen, from Yale University, found that the new Hubble observations helped them confirm that DF2 is not only farther from Earth than some astronomers suggest, but also slightly more distant than the team's original estimates. “ So the mystery of why DF2 is missing most of its dark matter still persists.”