WASHINGTON (AP) -- Astronomers are puzzling over an extraordinary cosmic blast in a distant galaxy.

The gamma-ray explosion was observed on March 28 by NASA's Swift satellite. Flaring from such an event usually lasts a couple of hours.
Scientists say this blast is unusual because the effects are long-lasting. More than a week later, they continue to see high-energy radiation spiking and fading at the source.
The burst was likely caused by a star that was ripped apart after drifting too close to a supermassive black hole.
Since the explosion, the Hubble Space Telescope and Chandra X-ray Observatory have focused on the aftermath. Hubble will observe if the galaxy's core changes brightness in the coming days.
The galaxy is 3.8 billion light years from Earth. A light year is about 6 trillion miles.