They thought they were studying some renegade stars in the exurbs of the giant Andromeda Galaxy. Instead, a team of astronomers from Case Western Reserve University discovered they were looking at a whole new galaxy - one with a serious death wish.
“We didn't have a clue!” said Heather Morrison, the astronomer leading a four-member research team. “We thought we were studying the big galaxy, ...what we found instead was a whole new object.”
The new galaxy, dubbed Andromeda VIII, is bumping into the Andromeda Galaxy -which is our Milky Way's nearest galactic neighbor, some 2 million light years away.
The Case researchers were probing the eccentric behavior of stars in the outer reaches of Andromeda when they uncovered the new dwarf galaxy. These outer stars follow comet-like orbits, plunging into the center of the galaxy instead of circling sedately with the other stars.
“We got velocities for the big stars, then we found a group with exactly the same velocity just moving completely wrong to be members of the big galaxy,'' Dr. Morrison said.
The astronomers caught the galaxy in the middle of some deadly behavior.
“One of the coolest things about this is we've caught it in the act,'' Dr. Morrison said. The new galaxy is already stretching under the influence of Andromeda's gravity. Andromeda has some 100 billion stars extending across 180,000 light-years. Andromeda VIII has an estimated 100 million stars, across 30,000 light-years.
Andromeda's gravity will eventually pull the dwarf galaxy like taffy, until, in 10 billion years, it's nothing but a ribbon of stars wrapping the bigger galaxy.
Steve Marin, spokesman for the American Astronomical Society and astronomer at NASA's Goddard Space Flight Center in Greenbelt, Md., said the significance of the discovery is that the galaxy is so close. “There are only a few dozen galaxies that close to us in space,” he said.
He said that while thousands of new galaxies are discovered regularly in deep space, only one or two every couple of years are discovered amid what are called local galaxies.