An ancient eruption of a supermassive black hole in the Milky Way may have inflated two huge bubbles of gamma rays which were just now discovered and are considered a new type of astronomical object.
"It shows, once again, that the universe is full of surprises," said Jon Morse, director of astrophysics at NASA headquarters.
Combined, the bubbles, which are aligned at the center of the Milky Way, span a vast distance of about 50,000 light-years. The structures are very distinct, with defined edges, and have as much energy in them as 100,000 supernova.
They were found with NASA's Fermi Gamma-Ray Telescope, which surveys the sky every three hours for the highest-energy light.
Among the 1,500 sources of gamma rays Fermi has mapped so far, nothing resembles the bubble-shaped structures, which stretch across more than half of the visible sky, from the constellation Virgo to the constellation Grus.
