Those Improbable Quasars

Two years ago, in what sadly was his last editorial for Analog, John Campbell summarized the problems presented by those maddening quasars—problems that have driven astronomers and cosmologists to frustrated gibbering.

He titled the editorial "Those Impossible Quasars." Today we might be on the verge of moving the quasars from the category of "impossible" to a tamer "improbable." And it's rather fitting, too, that some significant breakthroughs have been made in this tenth anniversary of the year in which the quasars were first recognized to be something extraordinary in the heavens.

Don't begin celebrating yet. The quasars may still be doing things that are well beyond our understanding of physics. But it begins to look as if their uniqueness, their strangeness, is as much a matter of human interpretation as of actual, physical fact.

The quasars have not yet been tamed to the point where they can be fit snugly into one of the grand cosmological schemes that university professors are so fond of. They are still, in the words of Sir Winston Churchill, "a riddle wrapped in a mystery inside an enigma. But it's at least beginning to look as if they're not completely different from everything else in the universe, and not completely beyond our powers of understanding. As long as we're quoting famous men, it was Albert Einstein who said, "The eternal mystery of the world is its comprehensibility."

The quasars were first noticed as early as 1960, when astronomers found that there were several strong radio sources that seemed to coincide with the locations of rather inconspicuous blue stars. They were assumed to be stars in our own Milky Way galaxy, and astronomers rejoiced that "radio stars" had at last been discovered. Since the beginnings of radio astronomy, researchers had been trying to find stars that were both optically bright and strong radio emitters, because then the two techniques of observation could be compared against each other on the same objects. Most stars are generally quiet in radio output; our own sun, for example, does not emit much radio energy—except when a solar flare erupts.

By 1963 it was certain that the "radio stars" were not stars at all. Optical astronomers couldn't get an intelligible spectrum from any of them. Then Maarten Schmidt of the Mt. Palomar Observatory guessed that what was being looked at were redshifted spectra. (Note: The physical evidence was practically useless without an astute interpretation.)

The spectra of these puzzling objects were indeed found to be red-shifted, by considerable amounts. Astronomers started calling them "quasi-stellar objects" or "quasi-stellar radio sources." In 1964 Hong-Yee Chiu, of Columbia University, coined the term "quasar," for which English language purists have never quite forgiven him.

The quasars posed such formidable problems for astronomers and cosmologists that many of them fled the scene, leaping gladly to newer (and easier) problems such as pulsars, neutron stars, X-ray sources, and black holes. Well, all right, black holes are far from easy when it comes to the physics of the problem. But the quasars did appear to be truly impossible.

If their redshifts meant that they were "cosmologically" distant—the standard Hubble-type explanation that equates redshift with distance—then the quasars were out among the farthest of galaxies. Very quickly, quasars with enormous redshifts were found, and early in 1973 two quasars with redshifts of more than ninety percent of the speed of light were discovered.

The Hubble-type explanation says that the redshifts are Doppler shifts, caused by the objects moving away from us. They are moving away because the universe is expanding. The bigger the redshift, the farther the object. The quasars that show recession velocities of more than ninety percent of light-speed must, therefore, be more than ten billion light-years away. This is not only very close to the theoretical limits of how far we can see into space, it also means that we're seeing these objects at close to the time that most cosmologists have fixed as the very beginning of the universe!

If the redshifts can be interpreted (there's that word again!) as being equated to distances.

Following that line of interpretation, if the quasars are so distant, yet such powerful emitters of energy, they must be putting out more energy—radio, infrared, visible light, ultraviolet—than a hundred galaxies of the Milky Way's size. But they're far smaller than galaxies!

Quasars flicker. Their energy emissions vary. They get stronger or weaker over periods ranging from a day or so to many months. This means that the body emitting the radiation can't be more than a light-day or, at most, several light-months, in diameter. Contrast this to a typical galaxy, which is many thousands of light-years wide! A light-day is about three times the diameter of Pluto's orbit. How can you explain a body that's scarcely three times larger than the Solar System pouring out more energy than a hundred Milky Way galaxies?

You can't. And neither can anyone else.

So when it was discovered two years ago that the two components of the quasar 3C 273 are flying away from each other at ten times the speed of light, it was a case of adding another straw to an already broken back.

The speed of light is an absolute limit, any physicist will tell you. Nothing in this universe can move faster than light-speed, c. There is no way that 3C 273's two components can be moving away from each other at 10 c.

Again: it's not the evidence by itself that counts; it's the interpretation.

Since the earliest glimmerings of the quasar puzzle, a small but persistent group of astronomers, physicists and cosmologists have been insisting that the quasars are not "cosmologically" distant, but are instead relatively nearby, "local" objects—only a few tens of millions of light-years away, rather than billions. These thinkers believe that the quasars' redshifts are not part of the expansion of the universe and cannot be related to their distances. They claim the quasars are "local": not in our galaxy, not even in our Local Group of galaxies, but certainly not out at the edges of the observable universe.

There is much to recommend the idea that quasars are "local" objects. (I even wrote an article for the June 1968 Analog that suggested the quasars are actually interstellar spacecraft within our own galaxy. My tongue was in my cheek, of course, but not all the way.)

If the quasars are "local," then 3C 273 isn't flying apart at 10 c. The estimated energy outputs of the quasars come down to something more easily handled—only a fraction of a galaxy's output. Their sizes, as deduced by their twinkling, fall more in line with what we would expect. The quasars begin to look like large star clusters, perhaps a million solar masses in size, but far smaller and less energetic than a ten-billion-solar-mass galaxy.

But then, what causes the red-shifts?

Fred Hoyle and William Fowler suggested a decade ago that the quasars were indeed supermassive stars (or star clusters), and the redshifts were caused by gravitational stress on the photons struggling away from their surfaces.

Other astronomers, such as Allan Sandage, have suggested that the quasars are something the size of a major star cluster that's been fired out of its parent galaxy by an explosion in the galaxy's core. In this view, the redshift is caused by actual speed of recession, but the motion has nothing to do with cosmological expansion of the universe. When asked why we see only quasars flying away from us, these astronomers point out that blue-shifted quasars would be extremely difficult to detect for a variety of valid reasons. Besides, some suspected quasars have shown no measurable redshifts; perhaps they are blueshifted, and have been hurled out of parent galaxies toward us.

Question: If this interpretation of the redshift evidence is correct, what about the redshifts of ordinary galaxies? Do we live in a universe that has redshifted galaxies, for one reason, and redshifted quasars, for another? Or is the universal expansion of the universe, the whole Hubble redshift-distance relationship, merely an incorrect interpretation of the evidence?

Perhaps the universe is not expanding, after all.

Most cosmologists would succumb to apoplexy, if that turned out to be true. Thankfully for their physical and emotional well-being, it appears that it's not true. The latest evidence shows strongly that the quasars are truly "cosmological" objects.

For one thing, as John Bahcall of the University of California (Berkeley) has shown, the larger a quasar's redshift, the dimmer it appears to be. This is what you would expect if increasing redshift means increasing distance.

Then Jerome Kristian of the Mt. Palomar Observatory has pointed out that on every photographic plate taken with the 200-inch telescope where the redshift of the quasar is small enough so that an astronomer would expect to be able to see a galaxy at that distance, a faint image of a galaxy does indeed appear—surrounding the quasar! For the most distant quasars, no galaxies are seen, because the distance is too great; not even the 200-inch "light bucket" could pick up a galaxy at such distances.

More evidence comes from much closer at hand—within our own Milky Way galaxy, in fact. Studies of the motions of individual stars, and of gas clouds at the core of our galaxy, lead to the conclusion that the Milky Way is expanding. This has brought up a new round of arguing about the old idea that galaxies evolve from spirals into elliptical types. But the main point here is that the center of our galaxy is spitting out material—in the form of gas and stars—material that probably goes into the formation of the spiral arms that coil about the galaxy's core.

This new finding, which has been confirmed by observation of other galaxies where much the same thing is happening, has also helped to explain one of the puzzles of modern astrophysics: gravity waves.

Joseph Weber of the University of Maryland, the pioneer observer of gravity waves, from space, has been roundly criticized lately because there has been no satisfactory explanation for the amounts of gravitational energy he claims to have observed.

Weber believed that his "telescope"—a 3.5-ton cylinder of solid aluminum coated with piezoelectric motion detectors`—had detected gravity waves given off by massive stars undergoing, supernova explosions and collapsing into neutron stars or black holes. But the amount of gravitational radiation he claimed to detect was too much for other scientists' to believe—more than one hundred times the mass of the sun would have to be converting itself into gravitational energy per year to account for Weber's data. At a conference at Oxford last April, both American and British astrophysicists scoffed at Weber's claims.

But the information about the Milky Way's expansion throws new light on the subject. Something like a hundred times the mass of the sun could be sweeping past our Solar System every year, mostly in the form of interstellar hydrogen gas. This could be what Weber is detecting.

Moreover, when this internal expansion of the Milky Way is put alongside all the other evidence that galaxies have very active, even explosive, cores—then the quasar puzzle begins to fall into place.

The Milky Way and other "normal" galaxies are constantly spewing material out from their cores. At least one small galaxy (M 82) and one very large one (M 87) are known to have exploded. Seyfert type galaxies have very bright, turbulent cores. And the quasars just might be other, much more violent forms of explosion at the cores of very distant galaxies. In many cases, the galaxies are so distant that we cannot see them at all, only the incredible brilliance of their core explosions.

When John Campbell called the quasars "impossible," he concluded that perhaps they were actually the collapse of whole galaxies into black holes. That was a popular interpretation a couple of years ago, when black holes were the newest playthings for astrophysicists and cosmologists.

But the new interpretation (that word again!) pictures just the opposite event. Instead of a galaxy collapsing and dying, the quasars—if they are galactic core explosions—might represent the birth of new galaxies.

The quasars are very distant, and therefore very old. What we may be seeing, then, is the unbelievably violent birth of new galaxies, formed in explosions that can only be explained by the violent collision of matter and antimatter. No other energy source can possibly account for the titanic brilliance of the quasars. The other, milder versions of galactic core explosions—including the expansion of the Milky Way's core—may be the settling-down process after the original explosion, the "last hurrah" of a galaxy-producing explosion.

There are still many staggering questions to answer, even if this highly speculative interpretation proves to be correct. Why do galaxies begin as explosions? Where does the original matter and energy come from?

Perhaps what we are seeing is an origin of the cosmos that is neither Big Bang nor Steady State, but rather a collection of Smaller Bangs that form the galaxies. It might go on indefinitely, continuously. At any rate, this interpretation might explain why the universe exists in quantum lumps called galaxies, rather than as a smooth continuum of stars and gas.

And, of course, if this interpretation is correct, and the quasars are very distant objects, then 3C 273 really is expanding at ten times the speed of light.

How do you interpret that?

THE EDITOR