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Tuesday afternoon, astronomers thought they saw a powerful explosion in the nearby Andromeda galaxy.

The Internet went wild with speculation about what it could be: Had two superdense neutron stars collided? Did a supermassive star explode?

"When I got up this morning and turned on my phone, I had a lot of emails and my Twitter feed was burning," says Phil Evans, an astronomer at the University of Leicester in Britain.

Evans is on a small team of intergalactic storm chasers. Their job is to spot gamma ray bursts, blasts of light from far-off violent explosions. These bursts are by far the most powerful explosions in the universe.

"During its entire normal lifetime, our sun will give off less energy than a gamma ray burst will in a few handfuls of seconds," Evans says.

The bursts are brief. So to catch them, astronomers have built a special satellite that scans the sky. When it thinks it sees a burst, it swivels to take a closer look.

It also sends a text alert to the astronomers' phones. There's a team on call, 24-7. The astronomers have a telephone conference and issue a report to other astronomers, telling them where in the sky to look for follow-up observations.

Yesterday afternoon's alert was particularly exciting because the Andromeda galaxy is relatively nearby. Normally gamma ray bursts are a lot farther away, so this would be a rare opportunity to study one up close.

Unfortunately, it wasn't a gamma ray burst that had been detected Tuesday. A software glitch had prevented some of the data from reaching the ground. It turned out to be a false alarm.

"In a sense we're to blame for putting something out there that wasn't true, but that's actually part of what the job involves at times," Evans says.

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