Hints of a new solar system
It is in the highest degree unlikely that this earth is the only one to have been created.
—Lucretius, 1st century B.C.
Vega is one of the brightest stars in the summer sky; in the Northern Hemisphere it is visible almost directly overhead in the constellation Lyra. About 60 times as luminous as the sun, this glowing beacon is often used by astronomers to calibrate their instruments and judge the brightness of other celestial bodies. Now scientists have another reason to keep an eye on this prominent star. Last week Caltech's Jet Propulsion Laboratory announced that an orbital telescope, the new Infrared Astronomical Satellite (IRAS), appears to have found the first direct evidence that a far-off star could be encircled by planets of its own.
Scientists have long assumed that stars beyond the sun are the hubs of their own solar systems. Indeed, some of these worlds may include planets where life perhaps has evolved. Yet even the closest stars are too distant for earth-bound telescopes to discern any planets in orbit around them. Indications that Vega, which lies 26 light-years (150 trillion miles) away, has a solar system may be the most important finding so far made by IRAS, a joint effort of the U.S., Britain and The Netherlands that was launched last January. When Astronomers H.H. Aumann of the Jet Propulsion Laboratory, which manages the project for NASA, and Fred Gillett of Kitt Peak National Observatory in Arizona aimed the instrument at Vega, they detected an unexpectedly strong flood of infrared radiation, or heat. (IRAS is the first orbital telescope that operates in the infrared frequency range, taking the temperature of the various components of the universe.)
Aumann and Gillett quickly realized that the heat was coming not from the star but from the region around it, extending out about 7.4 billion miles, or twice the distance to Pluto, the sun's outermost known planet.
How to explain these readings? Unlike the 4.6 billion-year-old sun, Vega is a veritable infant. It is less than a billion years old. At that age, it is probably still surrounded by an envelope of the cosmic debris, consisting of dust and gases, out of which all stars as well as their families of planets are apparently formed. IRAS'S sensors indicated that the temperature of this free-floating matter was a chilly -300° F, about the same as that of Saturn's innermost rings, which are made of small chunks of matter. Further calculations showed that individual particles in the mass surrounding Vega had to be at least the size of buckshot; as the astronomers noted, anything smaller would already have been drawn into Vega by its powerful gravity. Only larger clumps—accumulations of material the size of asteroids, moons and perhaps even planets—would still be orbiting the star. Life, however, would probably not yet have had time to emerge.
Many of these conclusions, of course, are purely speculative. The infrared eyes of IRAS, as remarkably sensitive as they are, are not sharp enough to pick out any separate objects at such a great distance. Still, indications are that in the cosmic debris swirling around Vega there is a solar system in the making. Now it will be up to more powerful eyes, either on earth or in orbit, to get a better look at this new world.