Researchers compact elliptical galaxies have found a total of 11 runaway galaxies which have escaped from the runaway galaxies that they used to call home.
Researchers already know of lots of runaway moons, runaway planets, runaway stars and even a runaway star cluster. For an object to be ejected from its cosmic home, it needs to move faster than escape velocity. For example, a runaway star needs to move at more than one million miles per hour to escape its galaxy. To escape its galactic cluster, a galaxy has to move at an estimated 6 million miles per hour which is more than 1800 miles per second.
“These galaxies are facing a lonely future, exiled from the galaxy clusters they used to live in,” said astronomer Igor Chilingarian in a statement.
Chilingarian is with the Harvard-Smithsonian Center for Astrophysics and Moscow State University, and the lead author of a paper describing the rogue galaxies appearing in the journal Science.
Chilingarian and his co-author, Ivan Zolotukhin were using public data archives from the Sloan Digital Sky Survey and the GALEX satellite to search for compact elliptical galaxies. Compact ellipticals are smaller than a typical galaxy, usually only a few hundred light-years across. For comparison, the Milky Way is 100,000 light years across and has 1000 times more mass than a typical compact elliptical.
Only 30 compact ellipticals had been found prior to the research and Chilingarian and Zolotukhin managed to increase that number by 200. Of those 11 were completely isolated and too far from any galaxy or galactic cluster to be associated with it.
According to prior theories, the isolated galaxies should not exist. Scientists thought that the compact ellipticals were once large galaxies, stripped of their stars through collisions with even larger galaxies. So, compact ellipticals were expected to be located near very large galaxies.
“The first compact ellipticals were all found in clusters because that’s where people were looking. We broadened our search, and found the unexpected,” said Zolotukhin.
The team believes that the rouge galaxies may be a result of three galaxy collisions; A compact elliptical is stripped of its stars by a large galaxy and then an even larger galaxy collides with the pair, throwing the tiny galaxy free of the gravitational pull of either of the larger ones.
The researchers say that the discoveries represent a victory for the Virtual Observatory (VO). Coordinated by the The International Virtual Observatory Alliance (IVOA) the VO is a project to make data from astronomical surveys accessible to researchers for data mining and, hopefully, result in finds not anticipated by those who originally gathered the data.
“The IVOA now comprises 20 VO programs from Argentina, Armenia, Australia, Brazil, Canada, Chile, China, Europe, France, Germany, Hungary, India, Italy, Japan, Russia, South Africa, Spain, Ukraine, the United Kingdom, and the United States and an inter-governmental organization (ESA)” according to the website.
