Our Milky Way galaxy is a messy eater, leaving streams of star "crumbs" spread across the sky after chomping its smaller neighbors, a new study reports.
Astronomers have found two such streams emanating from the Sagittarius dwarf galaxy, torn off by the Milky Way's huge gravitational pull. The two newfound star tails are in the southern galactic hemisphere, and they meet up with two others previously known from Sagittarius in the northern galactic hemisphere.
"Sagittarius is like a beast with four tails," study co-author Wyn Evans, of the University of Cambridge in the United Kingdom, said in a statement.
Sagittarius used to be one of the brightest of the Milky Way's satellite galaxies. But the Milky Way's immense gravity has torn it apart, dispersing half of Sagittarius' stars and virtually all of its gas over the last billion years or so, researchers said. [Video: Milky Way Shreds Dwarf Galaxy into Four Star Streams]
"That was an amazing discovery," said lead author Vasily Belokurov, also of the University of Cambridge. "But the remaining piece of the puzzle, the structure in the south, was missing until now."
The researchers looked at maps of more than 13 million stars, eventually spotting the two new star streams branching off from Sagittarius. One stream is fatter and brighter than the other, and it's more enriched with iron and other metals than its dimmer companion, researchers said.
The researchers aren't sure what caused the galaxy's star tails to split. One possibility, they said, is that Sagittarius was once part of a binary galactic system, like the present-day Small and Large Magellanic Clouds. Sagittarius and its putative partner could each have generated a leading and trailing tail upon falling into the Milky Way, yielding four streams in total.
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