Galactic 'blazar' lights up heavens

A "blazar" - a source of energy which shines more brightly than 10,000 Milky Way galaxies put together - has been detected by astronomers in the southern skies, 2 billion light years away from Earth.

A monstrous black hole 100million times bigger than our own Sun, is believed to lurk at the centre of this active galaxy, feeding on the gas and dust its gravity is sucking into it. The black hole converts this matter into the huge amounts of energy which make it detectable from Earth.

According to Claudia Megan Urry, of the Space Telescope Science Institute, the blazar betrayed its presence by a huge flare of radiation, starting with a burst of X-rays detected by a Japanese satellite called ASCA.

She said these X-rays were followed within a day by a corresponding flare in the extreme ultraviolet radiation, followed yet later by a flare at less energetic ultraviolet wavelengths. Out of an estimated 50 billion to 200 billion galaxies in the entire universe, "we know only a few hundred blazars" Dr Megan Urry said.

Blazars are the brightest and most variable phenomena ever seen in the sky. Yet, despite their brightness, their variability suggests that all that energy comes from a region of space little larger than our own solar system. Other galaxies are believed to have black holes lurking at their centre, but this is usually surrounded by a gigantic ring of gas and dust which hides direct view of the black hole.

In a few of them however some of this gas, heated to temperatures of millions of degrees, escapes at nearly the speed of light from the axis of the ring. Blazars are those galaxies where these jets, focused like the nozzle of a rocket engine, are pointing to Earth. This gives astronomers a rare glimpse directly down the throat of the jet to the innermost region surrounding the black hole.