The Questions of Quasars

What is a quasar? Answers were almost as numerous as the astronomers who turned up at the Montreal meeting of the American Association for the Advancement of Science. New theories about the nature of "quasi-stellar sources" have only generated new arguments; new observations have only enlarged the uncertainty. About all that the assembled scientists could agree on with confidence was that Dr. Maarten Schmidt of Mt. Wilson and Palomar observatories was the proper choice for astronomy's prestigious Helen B. Warner prize.

The modest, good-humored stargazer, who was born in The Netherlands and educated at Leiden University, did his most productive research after he came to the California observatories and became a professor at Caltech. He likes to deprecate his own achievements, but his colleagues agree that no man has contributed more to the study of the puzzling quasars that dot the universe.

Dim Stars. Confusion about quasars began nearly 20 years ago when radio telescopes first found concentrated sources of powerful radio waves at unexpected points in the sky. Some of these sources turned out to be well-known objects such as galaxies, but others were not so easy to identify. At the spots where the radio waves came from, optical telescopes could find nothing except what appeared to be dim stars.

For a while, astronomers tried to explain how such ordinary-looking stars could produce large quantities of radio waves. But they made no progress, and two years ago Dr. Schmidt made things worse. With Dr. Jesse Greenstein, Schmidt photographed the spectra of four of the radio-loud "stars" with the 200-in. Palomar telescope and found evidence of ultraviolet light that had increased in wave length until it became visible light.

Fastest and Farthest. Such wave lengthening, which astronomers call a "red shift," is the familiar tool used to measure the speed of objects moving away from the earth. The fastest of the mysterious objects measured by Dr. Schmidt proved to be speeding away at 76,000 miles per second, which is about half of the speed of light.

According to the rules of the expanding universe, speed of recession is proportionate to distance. This reckoning places Dr. Schmidt's quasars at least four billion light-years away from the earth; it makes them the most distant objects yet identified. Obviously they cannot be anything like stars. To be visible at such an enormous distance, a luminous object must give as much light as 50 entire galaxies, each containing an average of 100 billion stars.

Astrophysicists have not yet figured out any satisfactory mechanism capable of producing so much energy, which outranks in brilliance anything else in the universe. They have beat the relativistic bushes, imagining giant stars that collapse with the speed of light: they have theorized about galaxies with negative mass, or tight clusters of extra-large stars that detonate like supernovae when a shock wave passes through them. But none of these ideas has won acceptance, and none has begun to explain the fact that quasars flicker strangely, varying in brilliance as much as 10% a month.

Since nothing can travel faster than light, any object that changes in brilliance cannot be larger than the distance light would travel during the period of fluctuation. Even the crowded nuclei of normal galaxies are many thousand light-years in diameter, so no known influence could cross them quickly enough to make them flicker on a monthly tempo. An object that flickers so fast would have to be less than one light-year in diameter, unless it follows physical laws that are wholly unsuspected by human scientists.

Blue Birth. The confusion has increased steadily. Dr. Allen R. Sandage of Mt. Wilson and Palomar reported that a radio source, 3C-2, which was photographed as a dim reddish object only two years ago by the University of Minnesota observatory, has shown up in recent Palomar pictures four times as brilliant as before, but rich in blue light. It seems as if 3C-2 has turned into a quasar, giving a vast increase in shortwave radiation. But no one can imagine a process that could kindle such an outburst in so short a time.

Another unsettling bit of news is that quasars may not be scattered like galaxies--at random around the universe. Instead, the 34 quasars that are now known seem to favor a plane that is tilted slightly away from the plane of the Milky Way galaxy. It is almost unthinkable, however, that the most distant observable objects may have a plan of arrangement. Can the universe itself, the astronomers ask, have a definite shape? Or is the region that they have been in the habit of calling the universe merely a detail of a larger and still unimagined structure? Clearly, the questions raised by quasars open a new chapter in astronomy.

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