The whole thing looks like a ring to us on Earth because we’re seeing the collision head-on, rather than from the side.
"We see a ring-like structure that is distinct from the galaxies," Jee said.
Another cluster collision in what’s called the Bullet Cluster was reported last year and also showed some separation of dark matter, but it was a side view of the same sort of event. It’s very useful to now have a second view from a 90-degree different perspective, said astronomer Richard Massey of the California Institute of Technology.
"It’s really exciting if it’s right," said Massey.
For one thing, having a clear case showing where dark matter is separated from what we consider ordinary matter may make it possible to study dark matter by itself, which might lead to important clues to what exactly the enigmatic stuff is.
Massey and other researchers would like some independent researchers to check and confirm the discovery. However, that’s not going to be easy to do, since the instrument on Hubble that was used for the discovery — the Advanced Camera for Surveys — stopped operating last year.
It’s possible a future space shuttle mission might repair the Hubble instrument, Massey said. If not, there are some other satellite observatories in the works which might be able to continue the dark matter research.
