Two space telescopes have recently provided new insight into the nature of the strange filament , which is now believed to be a giant intergalactic shock-wave ( similar to a sonic boom but traveling in intergalactic gas rather than air ) caused by one galaxy ( NGC 7318B ) falling into the center of the group at several millions of miles per hour .
It is now believed to be a giant intergalactic shock-wave ( similar to a sonic boom but travelling in intergalactic gas rather than air ) . This is caused by one galaxy ( NGC 7318B ) falling into the center of the group at several million miles per hour .