Twinkle of stars confounds astronomers

SAN DIEGO, Dec. 3 (UPI) -- U.S. astronomers say they've observed waxing and waning of distant exploding stars that don't match up with current knowledge of the cosmic explosions.

Using a sensitive instrument aboard a satellite that images the entire sky, astronomers at the University of California, San Diego, studied four novae, or exploding stars, and recorded their brightness over the course of the outbursts, a university release said. Rebekah Hounsell, a graduate student at Liverpool John Moores University in Britain, studied the measurements while visiting UC San Diego.

Three of the novae stalled before reaching a peak of intensity and all flickered or flared for unknown reasons as the explosions ran their course, she found. A pause or "pre-maximum halt" in the brightening of novae had been observed before but was thought to be an anomaly.

The precise time-scale and repeated observations of the current study confirms the phenomenon, the researchers said.

"The reality of this halt as found in all three of the fast-declining novae observed is a challenge to detailed models of the nova outburst," astrophysicist Mike Bode of John Moores says.

Theorists have already begun to refine their models of how novae explode in response to the findings, the university researchers say.

The changes in intensity in the exploding stars may correspond to changes in the dynamics of the process that still need to be explained, scientists say.