Q U A S A R S E N G I N E S
Since their discovery in 1963, quasars have remained one of astronomy’s supreme enigmas. The most baffling of all their characteristics is that a typical quasar’s radiation surges from a compact region large enough for only a few dozen stars; yet a typical quasar generates the energies of tens or even hundreds of galaxies.
The quasar is a starlike object—its name is a contraction of quasi-stellar—but its prodigious energy output places it in a class all its own. Now new evidence strongly suggests that the engine that drives these titanic fountains of radiation may be nature’s ultimate force: the black hole. Black holes are gravity whirlpools that can swallow a beam of light, stop time, and curve space.
An object that falls into a black hole is forever removed from our universe. The hole absorbs any intruder and adds the intruder’s mass to its own. Close to the “edge” of a black hole, the gravitational force would be so strong that it would be roughly equivalent to that experienced by someone hanging from a bridge with half the population of Canada swinging from his ankles.
For all their power, though, black holes are relatively small compared with other cosmic objects. If the earth were condensed to a black hole, it would be approximately the size of a hazelnut.
Cambridge University’s Sir Martin Rees (Astronomer Royal) was one of the first astronomers to promote the idea that large black holes are the engines that drive quasars. “Black holes are one hundred times more efficient at producing energy than the thermonuclear burning at the core of a star like our sun,” he explains. Long before matter sucked into the hole reaches the point of no return, suggests Rees, the monstrous gravitational field accelerates it to nearly the speed of light generating an enormous amount of energy. This energy is eventually released as radiation before the doomed matter reaches the maw of the black hole.
Feeding a giant black hole one star—or its equivalent in dust and gas—every year would form a blazing, doughnut like, whirlpool around the hole that could churn out enough energy to equal that of a quasar. Consuming matter at this rate would eventually inflate the mass of the black hole to millions—and possibly billions—of times that of the sun. According to Rees’s calculations, a one-billion solar mass black hole would be small, about the diameter of Pluto’s orbit.
This is a tremendously significant finding, as astronomers now estimate there are well over 600 of these mysterious, super-bright sky objects. Astronomers and astrophysicists have suspected for more than 20 years that black holes were the engines that power the quasars. Until recently, however, the model scientists postulated involved no galaxies, just a disc of intensely hot gas that collected around the edge of a black hole. This is the first time a cosmic collision between galaxies has been suggested as the source of black-hole power.
One of the most important pieces of evidence supporting Rees’s scenario has been gathered by astronomer John Hutchings, of the Dominion Astrophysical Observatory, in Victoria, British Columbia. Using Hawaii’s Mauna Kea Observatory, an international facility, Hutchings has closely examined 80 quasars, which until recently had been seen as mere shimmering dots through most other telescopes.
The clear air above the summit of Mauna Kea has allowed Hutchings to distinguish the zone immediately around the quasar from the light of the quasar itself. Concentrated around the heart of the quasar, Hutchings has found what he calls fuzz. His delicate examination has shown that the fuzz is the light of billions of stars similar to those found in normal galaxies. “The evidence points to quasars being hyperactive nuclei of galaxies,” he reports.
In recent months, Hutchings’s research has revealed that some quasars are formes from two colliding galaxies. “The gas from one is stripped away and funneled to the center of the other to fuel the quasar engine.” Hutchings speculates that during such collisions a galaxy can become a quasar. And since astronomers are almost certain that all galaxies have black holes at their centers, these collisions could become “feeding time” for galactic black holes lurking in every galaxy.