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January 12, 2015

Astronomers around the world spent much of last year looking for fireworks from the center of the Milky Way galaxy. But like a Fourth-of-July show that’s been rained out, nothing happened. And one team of researchers says that may be because there no fireworks to set off in the first place.

The show was expected to come from an object known as G2, which was passing quite close to the supermassive black hole at the galaxy’s heart last spring. Many thought G2 was a large cloud of gas. The black hole was expected to gobble up some of the gas, which would flare brightly as it spiraled into the black hole.

But a team led by Andrea Ghez at UCLA says there was no cloud to begin with. Instead, the team’s observations suggested that G2 was a big star surrounded by a shell of gas and dust. The black hole stripped away streamers of the material around the star, but not enough to trigger any fireworks.

According to this scenario, the star was originally two stars that were orbiting the black hole as a pair. As the black hole’s gravity tugged at the stars, it made their orbit around each other unstable. Eventually, the two stars merged to make one star about twice as massive as the Sun. Debris from the collision formed a warm cocoon that’s a quarter-of-a-billion miles wide.

Other astronomers have different explanations for the lack of fireworks from G2. Whatever the cause, though, the center of the Milky Way has remained unexpectedly quiet.


Script by Damond Benningfield, Copyright 2014

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