Space Telescope Science Institute
NASA's Swift satellite, Hubble Space Telescope, and Chandra X-ray Observatory have teamed up to study one of the most puzzling cosmic blasts ever observed. More than a week later, high-energy radiation continues to brighten and fade from its location. Astronomers say they have never seen such a bright, variable, high-energy, long-lasting burst before. Usually, gamma-ray bursts mark the destruction of a massive star, and flaring emission from these events never lasts more than a few hours.
On Monday, March 28, 2011, the Swift satellite's Burst Alert Telescope discovered the source in the constellation Draco when it erupted with the first in a series of powerful blasts. Swift determined a position for the explosion, which is now cataloged as gamma-ray burst (GRB) 110328A, and informed astronomers worldwide. As dozens of telescopes turned to the spot, astronomers quickly noticed a small, distant galaxy very near the Swift position. A deep image, taken by Hubble on Monday, April 4, 2011, pinpointed the source of the explosion at the center of this galaxy, which lies 3.8 billion light-years away from Earth. That same day, astronomers used NASA's Chandra X-ray Observatory to make a four-hour-long exposure of the puzzling source. The image, which locates the X-ray object 10 times more precisely than Swift, shows that the source lies at the center of the galaxy Hubble imaged.
Astronomers previously have detected stars disrupted by supermassive black holes, but none have shown the X-ray brightness and variability seen in GRB 110328A. The source has undergone numerous flares. Since Sunday, April 3, it has brightened by more than five times. Although research is ongoing, astronomers feel the unusual blast likely arose when a star wandered too close to its galaxy's central black hole. Intense tidal forces tore the star apart, and the infalling gas continues to stream toward the hole. According to this model, the spinning black hole formed an outflowing jet along its rotational axis. A powerful blast of X-rays and gamma rays is seen if this jet is pointed in our direction.
Hubble observations of GRB 110328A's host galaxy were taken with the Wide Field Camera 3 in visible and near-infrared light. This Hubble image of the galaxy was taken in visible light. Astronomers plan additional Hubble observations to see if the galaxy's core changes brightness.