Quasar erupts with relativistic flair.

WR0039

On Nov. 13,1989, a seemingly ordinary quasar erupted in a 3-minute explosion of energy equal to nearly a million years' worth of solar radiation.

The outburst left a telltale mark on X-ray data compiled by the Japanese Ginga satellite. After scrutinizing those data, astronomers have now concluded that this was the fastest eruption of an energetic quasar ever detected.

The blast temporarily boosted the energy output of quasar PKS 0558-504 by 67 percent along the line of sight to Earth, they reported this week at the American Astronomical Society meeting in Philadelphia. That intensity poses a puzzle. Standard theory holds that a quasar's brilliance stems from the radiation of accelerating hot gases as they fall into a massive black hole at the center of a galaxy But the enormous jump in PKS 0558-504s luminosity, if it radiated equally in all directions, would create so much outward pressure that gravity's tug - even from a black hole - could not contain the matter, and the gases would stream away.

Ronald A. Remillard and Bruce Grossan of MIT, along with colleagues from Japan, propose an alternative explanation. They suggest that this quasar's overall X-ray outburst was less energetic than it appeared, confining itself to a single jet of radiation - like a flashlight that just happened to beam in the direction of Earth. Such a jet would become detectable if blobs of gas inside the quasar were moving toward Earth at speeds near that of light, Remillard says. The physical laws governing such relativistic motion dictate that the emission would appear to concentrate along the direction of motion and would seem to occur over a shortened time span. Remillard speculates that if other quasars radiate as jets pointing away from Earth, they may go undetected.