A burst of energy that lit up the sky Christmas Day 2010 has been explained as one of two possible star collision theories, scientists revealed in the journal Nature.

A 28-minute long gamma-ray burst was recorded that day by NASA's Swift observatory. Now, two papers from Nature attempt to explain the explosion using two models of star collisions, one within our galaxy and one billions of light years away. Both theories include at least one type of ancient star that was once many times the size of our own sun. In the scenario that may have taken place within our galaxy, researchers have theorized this collapsed star, called a neutron star, may have collided with a comet.

The comet may have broken up as it approached the star and the gamma-ray emission may have happened as the debris hit the star. The alternative idea is that two stars may have collided, a scenario where the neutron star may have been orbiting a normal star as that star entered its red giant phase. In the life cycle of some stars, they swell up like a balloon to form red giants, and during the blowing up phase, this star may have subsumed the neutron star. Once enveloped by the giant star's outer atmosphere, it would have eventually merged with the star's core and creating a black hole. That event would have been followed by a mass ejection of energy and a supernova. That's where the gamma-ray burst would have come from and based on this model, the event may have occrred nearly 5.5 billion light years away from the Earth.

"The beauty of the Christmas burst is that we must invoke two exotic scenarios to explain it, but such rare oddballs will help us advance the field," Chryssa Kouveliotou, a co-author of the supernova study at NASA's Marshall Space Flight Center in Huntsville, Ala said in a statement.
NASA's Swift was launched in November 2004 and is managed by Goddard. It is operated in collaboration with several U.S. institutions and partners in the United Kingdom, Italy, Germany and Japan.