Cannibal Galaxy Could Show How These Huge Structures Grow

Image of the Umbrella Galaxy, combining data from the 0.5-meter BlackBird Remote Observatory Telescope and Suprime-Cam on the 8-meter Subaru Telescope. Credit: R. Jay Gabany

There’s a hungry galaxy on the loose about 62 million light-years away from us. Astronomers just revealed that the Umbrella Galaxy (NGC 4651) is busy gobbling up another galaxy, similar to how our own Milky Way Galaxy is eating the smaller Sagittarius.

“This is important because our whole concept about what galaxies are and how they grow has not been fully verified,” stated co-author Aaron Romanowsky, an astronomer at both San José State University and University of California Observatories.

“We think they are constantly consuming smaller galaxies as part of a cosmic food chain, all pulled together by a mysterious form of invisible ‘dark matter’. When a galaxy is torn apart, we sometimes get a glimpse of the hidden vista because the stripping process lights it up. That’s what occurred here.”

This type of merger and acquisition is something you often seen moving about the universe, but it’s hard to capture these images in three dimensions, scientists said. It required looking at the motions of the stream you see here to see how the smaller galaxy is being torn apart.

“Through new techniques we have been able to measure the movements of the stars in the very distant, very faint, stellar stream in the Umbrella,” stated Caroline Foster of the Australian Astronomical Observatory, who led the study. “This allows us to reconstruct the history of the system, which we couldn’t before.”

The research was published in the Monthly Notices of the Royal Astronomical Society, and is available in preprint version on Arxiv.

Sources: Keck Observatory and Australian Astronomical Observatory