Gamma-ray burst mystery continues.

Just when astronomers thought they were about to solve the mystery of the origin of gamma-ray bursts--flashes of high-energy radiation that vanish without a trace--a new interpretation of a recent pair of Hubble Space Telescope images has revived controversy.

In March, researchers reported that ground-based telescopes had detected the first known optical counterpart of a gamma-ray burst. A week later, the counterpart was too faint to be seen with telescopes on the ground, supporting the notion that it represented a cooling fireball associated with the burst. Many researchers believe that the counterpart lies in another galaxy, clinching the theory that gamma-ray bursts originate outside our galaxy (SN: 3/22/97, p. 174).

Hubble images from March 26 and April 7 reveal that the faint visible-light source has two components, a pointlike object and an extended feature, report Kailash C. Sahu of the Space Telescope Science Institute in Baltimore and his colleagues in a March 31 circular of the International Astronomical Union (IAU).

In an April 17 IAU circular, Patrizia A. Caraveo of the Institute of Cosmic Physics in Milan and her colleagues report that the visible-light source appeared to move. Detectable motion implies that a source lies nearby, within our own galaxy.

Sahu and his collaborators say they find no evidence of motion. A third Hubble image may be needed to settle the controversy, he adds.