‘Astronomers have witnessed a cosmic explosion so strange they don’t even know what to call it. Although the blowup, discovered with NASA’s Swift satellite on March 28, emits high-energy radiation like a gamma-ray burst would, the event has now lasted for 11 days. Gamma-ray bursts last for an average of about 30 seconds.
Also unlike a gamma-ray burst, the explosion has faded and brightened, emitting staccato pulses of energetic radiation lasting for hundreds of seconds. 

“It’s either a phenomenon we’ve never seen before or a familiar event that we’ve never viewed in this way before,” says Andrew Fruchter of the Space Telescope Science Institute in Baltimore…’ (Wired)