Hubble sees the fireball from a "kilonova"

Kilonova Gamma Short Ray

NASA's Hubble Space Telescope has detected a new kind of stellar blast called a kilonova, which happens when a pair of compact objects such as neutron stars crash together. Hubble observed the fading fireball from a kilonova last month, following a short gamma ray burst (GRB) in a galaxy almost 4 billion light-years from Earth.

"This observation finally solves the mystery of short gamma ray bursts," says Nial Tanvir of the University of Leicester in the United Kingdom, who led a team of researchers conducting this research.

This sequence illustrates the kilonova model for the formation of a short-duration gamma-ray burst. 1. A pair of neutron stars in a binary system spiral together. 2. In the final milliseconds, as the two objects merge, they kick out highly radioactive material. This material heats up and expands, emitting a burst of light called a kilonova. 3. The fading fireball blocks visible light but radiates in infrared light. 4. A remnant disk of debris surrounds the merged object, which may have collapsed to form a black hole.

Gamma ray bursts are flashes of intense high-energy radiation that appear from random directions in space. They come in two flavors--long and short. "Many astronomers, including our group, have already provided a great deal of evidence that long-duration gamma ray bursts (those lasting more than two seconds) are produced by the collapse of extremely massive stars," explains Tanvir.

The short bursts, however, were more mysterious ( via ).

MORE: Gamma-ray burst 'hit Earth in 8th Century'

MORE: Surprise gamma-ray burst behaves differently than expected