Dark matter has disappeared in the galaxy and scientists don't know why

Esta instantánea del telescopio espacial Hubble revela una inusual galaxia

An unusual galaxy appears to lose its dark matter, scientists have discovered.

The unusual galaxy is challenging our understanding of how they form and evolve, researchers say after further detailed observations.

The latest study began when scientists deeply looked at a galaxy known as NGC 1052-DF2, or just DF2 for short. It's what astronomers call "UltraISO": although it's comparable in width to our own Milky Way, it contains only 1/200 of the number of stars.

The galaxy is strange in other respects: it does not appear to have the central region, spiral arms, or disk that are observed in many other galaxies.

And now scientists have confirmed what could be the most unusual part of the already strange galaxy. It seems to lack dark matter, which until now was understood as the necessary glue that helps galaxies form, holds them together, and make up the bulk of the universe.

Researchers first reported on the strange galaxy and its missing dark matter in 2018. But to verify the original findings, they looked back at the galaxy and tried to replicate their findings, as well as see if it's really inexplicable.

"We took a chance on our initial Hubble observations of this galaxy in 2018," said Pieter van Dokkum of Yale University, who led that original research. "I think people were right to question it because it's such an unusual result. It would be nice if there was a simple explanation, like an incorrect distance. But I think it's more fun and interesting if it's actually a strange galaxy."

To verify the findings, researchers must verify exactly how far away the galaxy is. If it is as far from Earth as researchers suggest, then the dark matter would only constitute a small percentage of its contents; some have claimed that it is, in fact, closer, and calculations of its dark matter are exaggerated.

This is because calculations about the amount of dark matter are based on how stars move in the galaxy, which can be used to infer the attraction of gravity within it. If it is as distant as scientists claim, then stars make up most of its mass and there is no room left for dark matter.

No, scientists did not just solve the massive dark matter mystery | WIRED UK

The new findings, based on observations from the Hubble Space Telescope, show that it is not only far from Earth, but even further away than those early estimates. It is 72 million light-years away, in contrast to the 42 million light-years proposed by other scientists and the 65 light-years suggested by the original research.

Read more: Biden calls on the US to 'eradicate systemic racism' during Juneteenth proclamation

That helps suggest that dark matter is indeed missing from the galaxy. But that opens up another mystery: why is the galaxy so deficient in dark matter, and what does that mean for our understanding of how galaxies form and hold together?

"For almost every galaxy we look at, we say we can't see most of the mass because it's dark matter," van Dokkum explained. "What you see is just the tip of the iceberg with Hubble. But in this case, what you see is what you get. Hubble really shows everything. That's it. It's not just the tip of the iceberg, it's the whole iceberg."

The new research is published in The Astrophysical Journal Letters.

Post a Comment