U.S. astronomers say a survey of galaxies observed along the sight lines to quasars and gamma-ray bursts creates a cosmic conundrum -- odd galaxy distribution.

The survey revealed a puzzling inconsistency: Galaxies appear to be four times more common in the direction of gamma-ray bursts than in the direction of quasars.

Quasars are thought to be powered by accretion of material onto supermassive black holes in the centers of distant galaxies. Gamma-ray bursts, the death throes of massive stars, are the most energetic explosions in the universe. But researchers say there's no known reason to expect galaxies in the foreground to have any association with these background light sources.

The result contradicts our basic concepts of cosmology, and we are struggling to explain it, said Jason Prochaska, associate professor of astronomy and astrophysics at the University of California-Santa Cruz.

Prochaska and graduate student Gabriel Prochter led the survey, which used data from NASA to obtain observations of the transient, bright afterglows of long-duration gamma-ray bursts.

The research -- which might have strange cosmological implications -- has been accepted for publication in Astrophysical Journal Letters.