Swift catches birth of black hole on camera

Living up to its name

By Lucy Sherriff, 11th May 2005

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Astronomers working on the Swift mission have photographed a gamma ray burst they think is likely to be the formation of a new black hole, 2.2bn light-years away. There was a flash of X-Rays just moments after the burst, which itself was very short-lived, followed by an optical afterglow. Astronomers think the explosion was caused by the merging of two neutron stars.

The Swift satellite is in orbit to investigate gamma-ray-bursts, the most violent, and mysterious explosions in the universe. It has been designed to respond rapidly to detection of gamma rays - within 20-70 seconds. This turn of speed is vital as the whole explosion can be over in seconds.

The satellite detected the gamma rays shortly after midnight, east coast time, on Monday this week, Space.com reports. Swift swung the rest of its sensors to face the explosion within 50 seconds, and just caught an X-Ray afterglow. Astronomers at larger, earth based observatories then went looking for the after-glow of the explosion in visible light.

This sequence, a short lived gamma ray burst followed by a short-lived X-ray burst and optical afterglow ,is the theoretical trademark of a merger of two neutron stars. But until now, the equipment available to researchers was not responsive enough or sensitive enough to do anything but detect the initial burst.

In this case, two neutron stars would have approached each other very gradually. "A fraction of a second before contact, the lower mass neutron star is disrupted and forms a neutrino driven accretion disk around the higher mass neutron star," Steinn Sigurdsson, a Penn State University researcher, told Space.com. "It implodes under the weight and forms a maximally spinning low-mass black hole."

At some point after its formation, the black hole emits a flare of superheated gases, travelling at relativistic speeds. This is when the gamma ray burst is created. ®