Cosmic 'enigma' yields its secrets
Quasars - once called the most enigmatic objects in the universe - have lost much of their mystery. A quasar (quasi stellar object) is a pint-size powerhouse that outshines a galaxy of a billion stars. Alan P. Lightman of the Harvard-Smithsonian Astrophysical Observatory notes that, were Boston a galaxy in terms of size and power output, a quasar would produce the power of the entire United States within the volume of a baseball.Skip to next paragraph
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How can anything so small be so powerful? Where does it fit in the cosmic scheme? Some experts had previously speculated that new kinds of physical laws were at work. Today, they need no such assumption.
Lightman told a recent American Physical Society session that quasars now have extended our knowledge of galaxies. He explained that, since the first quasar was discovered Aug. 5, 1962, ''evidence has accumulated to show a continuous range of energetic activity, starting with normal galaxies, going through active galaxies, and joining the less luminous quasars.''
Quasars may be powered by black holes. These are objects so compact that nothing escapes their powerful gravitational attraction.
Gas and dust falling into such an object release energy like falling water in a power station. If the gas has a magnetic field and the black hole rotates, this field can become tangled. This process extracts some of the black hole's rotational energy.
Lightman said the brightest quasars are now believed to use the ''water power'' effect. The less luminous quasars tap rotation.
Astronomers have also wondered whether quasars are distant or nearby. If they are close, their luminosity estimates would be so reduced they would no longer seem such prodigious powerhouses.
The so-called redshift sets the distance. The faster an object recedes, the redder its light appears. Also, in the expanding universe, the more distant an object is, the faster it recedes. Thus the reddening of its light indicates both speed and distance.
Quasar redshifts suggest vast cosmic distances. But doubters argue they are nearby objects whose light is reddened by processes other than recession. This dissent is fading. For example, Bruce Margon of the University of Washington and Ronald A. Downes and Hyron Spinrad of the University of California have found the first quasar clearly associated with a distant rich cluster of galaxies. Their report in Nature calls this ''further support for the argument for a cosmological interpretation of QSO [quasar] redshifts.''
Thus the quasars have yielded basic secrets. Lightman noted that ''our understanding of these distant objects will always be built upon a pyramid of uncertain inferences. . . .'' Yet, as cosmologist Michael Rowan-Robinson of Queen Mary College, London, observed last November in New Scientist, ''Today the drama remains but much of the mystery has been resolved.'' Is your nose a compass?
Magnetic material has been found in creatures as diverse as bacteria and birds. It often seems related to navigational ability. Recently three British scientists have found magnetic bone - bone containing ferric iron deposits - in the human sinus.