A blazar is an active galactic nucleus with a relativistic jet directed very nearly towards an observer. Relativistic beaming of electromagnetic radiation from the jet makes blazars appear much brighter than they would be if the jet were pointed in a direction away from Earth. The beams are created, says Halzen, as the super-sized black hole at the core of the galaxy eats stars, gas and dust at a frenetic pace. Not all of the material disappears into the black hole, however, as it sometimes saturates and spawns the relativistic jets characteristic of the blazar. At the center of most galaxies including our own Milky Way there's a gargantuan black hole that can have the mass of millions or even billions of Suns. In some galaxies, this supermassive black hole may collect a swirling disk of gas, dust and stellar debris around it to eat from. Gas, dust and the occasional star are captured and spiral into this central black hole, creating a hot accretion disk which generates enormous amounts of energy in the form of photons, electrons, positrons and other elementary particles. High-redshift blazars are some of the most extreme sources in the Universe. With jet power exceeding 10^47 erg s-1, they host billion solar masses black holes and are found up to when the Universe was only two billions years old. 49+271757.31, the most distant blazar observed to date, reveals important details about ancient black holes and places tight constraints on theories of the evolution of the universe. Its light originated when the universe was less than 1 billion years old, almost 13 billion years ago. A blazar is a feeding super-massive black-hole (SMBH) in the heart of a distant galaxy that produces a high-energy jet viewed face-on from Earth. Like other forms of active galactic nuclei (AGN), blazars are the most luminous and energetic objects in the known universe. “Blazars are extremely rare because it's not too often that a supermassive black hole's jet happens to point towards Earth,” said Francesco Massaro of the Kavli Institute for Particle Astrophysics and Cosmology near Palo Alto, Calif., and principal investigator of the research. Whereas the Energetic Gamma-Ray Experiment Telescope (EGRET) on NASA's Compton Gamma-ray Observatory identified 66 blazars during the mission, GLAST should see thousands. Its high-energy flares could unlock the foundations of the universe. They report, in two papers published in the journal Science, that blazars are a source of high-energy neutrinos elementary particles of the universe that could help trace the origin of cosmic rays. Blazars are also known to blast off from time to time. This giant flare can last from minutes to months. If Markarian 421 blasted off within range of our Galaxy, its jet would punch a hole straight through our Solar System. It would be a doomsday scenario, and there wouldn't be anything we could do to save ourselves.

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