Credit: University of Cambridge
The Milky Way galaxy is devouring its small neighboring dwarf galaxies
ScienceDaily — The Milky Way galaxy continues to devour its small neighbouring dwarf galaxies and the evidence is spread out across the sky.
A team of astronomers led by Sergey Koposov and Vasily Belokurov of Cambridge University recently discovered two streams of stars in the Southern Galactic hemisphere that were torn off the Sagittarius dwarf galaxy. This discovery came from analysing data from the latest Sloan Digital Sky Survey (SDSS-III) and was announced in a recent paper that connects these new streams with two previously known streams in the Northern Galactic hemisphere.
"We have long known that when small dwarf galaxies fall into bigger galaxies, elongated streams, or tails, of stars are pulled out of the dwarf by the enormous tidal field," said Sergey Koposov.
The Sagittarius dwarf galaxy used to be one of the brightest of the Milky Way satellites. Its disrupted remnant now lies on the other side of the Galaxy, breaking up as it is crushed and stretched by huge tidal forces. It is so small that it has lost half of its stars and all its gas over the last billion years.
Before SDSS-III, Sagittarius was known to have two tails, one in front of and one behind the remnant. Previous SDSS imaging had already found the Sagittarius tidal tail in the Northern Galactic sky in 2006 and revealed that one of the tails was forked into two.
"That was an amazing discovery," said Vasily Belokurov, from the University's Institute of Astronomy, "but the remaining piece of the puzzle, the structure in the South, was missing until now."