Photo: NASA/Swift/Stefan Immler, et al.
That's the aferglow of GRB 080319B, by far the brightest gamma-ray burst from a stellar explosion ever seen, as captured by NASA's Swift satellite. The burst was so bright that it could even be seen to the naked eye half-way across the universe:
Gamma-ray bursts are the most luminous explosions in the universe since the Big Bang and occur when massive stars run out of nuclear fuel. The stars' cores collapse to form black holes or neutron stars and release an intense burst of high-energy gamma-rays and jets of energetic particles.
The jets rip through space at nearly the speed of light, heating the surrounding interstellar gas like turbocharged cosmic blowtorches, often generating a bright afterglow.
"These optical flashes from gamma-ray bursts are the most extreme such phenomena that we know of," said Swift science team member Derek Fox, also of Penn State. "If this burst had happened in our galaxy, it would have been shining brighter than the Sun for almost a minute — sunglasses would definitely be advised."