Blazars may seem like something that came out of the imagination of an especially eccentric science fiction writer, but these extreme energy-emitting phenomena are real — and NASA's Fermi Gamma Ray Telescope has just discovered the most far-out ones yet.
Emitting an almost unreal amount of energy, blazars are super-powered, super-compact quasars that exist inside enormous elliptical galaxies and surround supermassive black holes at least a million times more massive than the sun. Fueling a blazar's electromagnetic ejections is what astronomers believe to be doomed matter from its black hole's accretion disc, which is exposed to intense heat and collapses as it falls into the chasm. When a small quantity of this matter is deflected into particle jets, it rockets into space in opposite directions at (almost) the speed of light. These jets make a blazar visible from the vicinity of Earth when they spew insanely bright gamma radiation right at us. Enter Fermi.
Led by Vaidehi Paliya and Marco Ajello of Clemson University, collaborating with Dario Gasparrini of the Italian Space Agency's Science Data Center and Roopesh Ojha of NASA's Goddard Flight center, the research team of astronomers who analyzed the Fermi images were astounded to see the most immense black holes that have ever been discovered in a blazar. Fermi's Large Area Telescope (LAT) detected these blazars by their gamma ray emissions. Gamma rays are the ghosts of radioactive decay, which occurs when atomic nuclei deplete their energy to emit radiation. The team was able to single out five previously undiscovered gamma-ray blazars from collected LAT data due to their brightness.
"We think Fermi has detected just the tip of the iceberg," noted Ajello, "the first examples of a galaxy population that previously has not been detected in gamma rays."
Blazars have been notoriously elusive when it came to being observed. More of them finally started appearing to a revamped LAT with heightened sensitivity at lower energies. Redshift revealed that light from these blazars began its space odyssey to Earth when the universe was only 1.4 billion years old, relatively young in terms of cosmic time. Redshift is increase in wavelength that shifts light emanating from faraway galaxies towards the redder, higher-wavelength end of the spectrum as that light moves away from the observer. Cosmological redshift is therefore proportional to the rate at which a source of radiation several million light years away moves further from Earth as the universe expands.
Astronomers are still looking to demystify how the black holes at the center of these blazars could have grown so monstrous in such a relatively short stretch of time. While galaxies and their black holes are believed to have grown over billions and billions of years through galactic mergers, how these mergers could have created supermassive black holes of this magnitude before the universe reached its billionth birthday is an enigma that needs further analysis.
"Despite their youth, these far-flung blazars host some of the most massive black holes known," said Ojha. "That they developed so early in cosmic history challenges current ideas of how supermassive black holes form and grow, and we want to find more of these objects to help us better understand the process."