Astronomers are tracking unusual, extremely bright blasts of radiation coming from the center of a galaxy 3.8 billion light-years from Earth.
Typically, a burst as powerful as the one seen in the Draco constellation marks the death throes of a massive star, but that's usually a one-time event. So far, the source has brightened four times since Tuesday.
The first sign of the event was on March 28 when the Swift gamma-ray detector picked up a burst. Automated messages went out to astronomers' cell phones and they quickly mobilized to get a better fix on the blast's location.
Follow-up observations showed the source was a distant galaxy. But most surprising is that the outburst didn't stop.
"Most gamma-ray bursts go off once and then they fade away into nothingness," astronomer Andrew Levan, with the University of Warwick in the United Kingdom, told Discovery News. "This burst went off four times in the space of two days and it carries on being bright even now."
Scientists suspect they are seeing a star being shredded by a black hole, a common enough phenomenon that looks different because of Earth's viewing angle. As a black hole consumes nearby matter, it generates extremely powerful jets, comprised of X-rays and gamma rays, along its rotational axis. Astronomers suspect a jet is pointed in our direction.
"People have talked about before what would happen when stars wander too close to their black holes, but no one has ever see that before in real-time," Laven said.
Ground- and space-based telescopes, including Chandra X-ray Observatory and the Hubble Space Telescope, have been tracking the burst, which was traced to the center of a dwarf galaxy.
Most galaxies, including our own Milky Way, have black holes in their centers, regions of space so dense with matter that not even light can escape their gravitational grip.
Astronomers are curious if the apparent star-feeding will trigger the galaxy's black hole to switch over into a more active phase. The galaxy, which is not named, is one of billions of star-forming dwarf galaxies.
"Theorists are busy trying to interpret our findings," Levan said.
The discovery also is likely to reshape understanding of how black holes rip up stars. Current computer models show such events lasting up to about a week at most, astronomer Neil Gehrels, with NASA's Goddard Space Flight Center in Maryland, told Discovery News.
"If this goes on for another week or so, we're going to be really baffled," Gehrels said.