Astronomy

A blazar is a very compact and highly variable energy source associated with a supermassive black hole. It is also characterized by a relativistic jet that is pointing in the general direction of the Earth. Blazars are among the most violent phenomena in the universe and are an important topic in extragalactic astronomy. Now, for the first time, astronomers have observed a blazar in action, substantiating a prevailing theory about how these luminous and energetic galactic cores work.

Two University of Michigan astronomers contributed to the research, which was led by Alan Marscher of the Institute for Astrophysical Research at Boston University. A paper on the observations is published in the April 24 issue of Nature.

Competing theoretical models currently sought to explain how this phenomenon occurs. One model predicted that the jets were propelled by magnetic fields that were twisted by the gravity of the black hole and the materials falling into it. This is the behavior the astronomers detected.

The scientists has observed the mechanism by which the acceleration of relativistic particles in the emanating jets occurs. Knowing that mechanism enhances our understand of the physics that goes into the acceleration process. Relativistic particles are particles traveling close to the speed of light. Though, it’s been difficult to catch these outbursts when they occur.

Scientists from across the globe aimed a variety of telescopes at the blazar BL Lacertae, about 950 million light-years away from Earth. Optical, X-ray and radio telescopes monitored the galaxy at different electromagnetic wavelengths periodically for several years. University of Michigan’s team successfully recorded radio light curves at the Radio Astronomy Observatory at Peach Mountain in Dexter. This is the first observational evidence that really fits with the picture that the theoreticians have had. Key factor of this evidence is a very fine sampling of a large number of instruments, including the Michigan radio telescopes.

Scientists hope to get a closer look at blazar jets when NASA launches its Gamma-ray Large Area Space Telescope (GLAST) satellite observatory in May.

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