Star burst hints at more black holes

January 15, 1991|By Luther Young | Luther Young,Sun Staff Correspondent

PHILADELPHIA -- A short, violent outburst of X-ray radiation from a distant quasar observed by U.S. and Japanese astronomers may boost estimates of the number of galaxies that harbor massive black holes.

The quasar -- located 2 billion light years from Earth -- erupted during a three-minute period in November 1989, producing energy equivalent to the sun's total radiation over a million years.

Billed as the fastest and largest increase in a quasar's output ever detected, the discovery was announced yesterday at the American Astronomical Society's meeting in Philadelphia.

"It's quite dramatic in what otherwise appears like a common, garden-variety quasar," said Dr. Ronald A. Remillard of the Massachusetts Institute of Technology.

Quasars -- the most luminous objects in the universe, shining with the energy of many galaxies -- exist at great distances from Earth, some nearly to the edge of the observable universe.

But their incredible energy appears to emanate from an area smaller than a single galaxy, perhaps as small as the solar system.

Scientists have postulated that quasars occupy the cores of distant galaxies and are fueled by black holes -- collapsed stars so massive that not even light can escape their gravity.

As stars and other matter are sucked faster and faster into a black hole, hot, glowing gases swirl into an "accretion disk" that can emit radiation more luminous than that from the nuclear fusion process powering our sun and other stars.

Theorists say the brightest quasars require black holes as massive as 100 million suns to produce their radiation energy, detectable billions of light years away.

Dr. Remillard said current estimates were that only 5 percent of quasars exhibit such "wild" behavior as very pronounced variations in energy output.

The quasar targeted by the researchers from MIT and several Japanese universities is known as PKS 0558-504, a distant body previously thought to be among the "tame" members of the species that radiate steadily.

But the unprecedented outburst was observed during an 11-hour observation of the quasar by the Japanese Ginga X-ray satellite, launched in 1987.

And the rapidity of the energy increase -- 67 percent in just three minutes -- sent the researchers scrambling to reconcile the event with theory.

Researchers spent considerable time double-checking the results before deciding to publish their data.

They speculated that, in a sense, the exceptional behavior of the radiation eruption could be an illusion.

Hurtled toward Earth as a jet of gaseous matter escaping at near the speed of light, it may have exhibited "relativistic beaming" predicted by Einstein, appearing larger and faster to observers than it really was.

An MIT graduate student, Bruce Grossan, compared the jet to a flashlight beam which just happened to be pointed at Earth.

He said it raises the possibility that more normal quasars and other active galaxies may have massive black holes and "flashlights going all over the place -- we just don't see them."

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