The "gamma-ray burst" seen on Christmas Day last year may have actually been a comet being eaten by a distant neutron star.
The gamma-ray emissions detected during the Dec. 25, 2010 event may not have been the result of an exploding star.
An alternative theory is that a comet strayed too close to a neutron star.
The neutron star's powerful tidal forces ripped the comet to shreds, generating prolonged gamma-ray emissions.
A burst of gamma-ray radiation from a distant galaxy, detected by an orbiting US telescope last Dec. 25, may have come from a comet crashing into a neutron star, astrophysicists suggest on Wednesday.
Gamma-ray bursts, or GRBs, are high-energy releases that often come from stars in their death throes.
The so-called Christmas Day GRB, spotted by NASA's Swift space telescope, has excited huge debate.
Its gamma emissions lasted for at least half an hour, whereas the typical GRB lasts from just a couple of second to a few minutes, and its emissions in the X-ray part of the energy spectrum faded much faster than usual.
Poring over the data, a team led by Sergio Campana of the Brera Astronomical Observatory in Italy believe that the strange event was caused by a minor body such as a comet or asteroid that flew so close to a neutron star that it was ripped apart by intense tidal forces.
Its crashing fragments produced a prolonged series of mini gamma-bursts.
Another explanation, offered by Christina Thoene of the Institute of Astrophysics in Andalucia, southern Spain, is that the big GRB was the merger of a helium star and a neutron star, which created a supernova.
The two papers are published in the British science journal Nature.