Harvard Smithsonian Center for Astrophysics | 2015 Apr 23
[c]We know of about two dozen runaway stars, and have even found one runaway star cluster escaping its galaxy forever. Now, astronomers have spotted 11 runaway galaxies that have been flung out of their homes to wander the void of intergalactic space.
This schematic illustrates the creation of a runaway galaxy. In the first panel, an
"intruder" spiral galaxy approaches a galaxy cluster center, where a compact
elliptical galaxy (cE) already revolves around a massive central elliptical galaxy.
In the second panel, a close encounter occurs and the compact elliptical receives
a gravitational kick from the intruder. In the third panel, the compact elliptical
escapes the galaxy cluster while the intruder is devoured by the giant elliptical
galaxy in the cluster center. Credit: NASA, ESA, Hubble Heritage (STScI/AURA)[/c]
"These galaxies are facing a lonely future, exiled from the galaxy clusters they used to live in," said astronomer Igor Chilingarian (Harvard-Smithsonian Center for Astrophysics/Moscow State University). Chilingarian is the lead author of the study, which is appearing in the journal Science.
An object is a runaway if it's moving faster than escape velocity, which means it will depart its home never to return. In the case of a runaway star, that speed is more than a million miles per hour (500 km/s). A runaway galaxy has to race even faster, traveling at up to 6 million miles per hour (3,000 km/s). ...
Isolated compact elliptical galaxies: Stellar systems that ran away - Igor Chilingarian, Ivan Zolotukhin
- Science 348(6233): 418 (24 Apr 2015) DOI: 10.1126/science.aaa3344