As astronomers uncover more and more evidence to suggest that our solar system is not unique, so too do they add more fuel to the argument that the conditions which on earth led to life are increasingly common.
20 years ago, astronomers searched for traces of flat, orbiting dust clouds around young stars. They eventually found them and thereby proved that as a star forms, it emerges from a rotating flat disk of gas which could also be the building ground for planets. Then in the 1980's they discovered several nearby stars such as Beta Pictorus which has, not only such disks but zones within them where material was mysteriously absent. This meant that something like a collection of planets could have swept clean the interplanetary dust cloud in these rotating disks leaving behind an empty region.
Then about 5 years ago, astronomers studying a distant pulsar detected the motion of at least two planet-sized bodies orbiting the pulsar; the first confirmed detection of planets beyond our solar system.
Finally, in the last few years, astronomers have detected the motion of Jupiter-sized planets orbiting the stars 51 Pegasi, 70 Virginis and 47 Ursa Majoris. As the above figure shows, we now know of something like 40 planets outside our solar system orbiting nearly as many stars!
Biologists are equally convinced that the conditions leading to the first reproducing organisms on the Earth were easily brought together and not at all special. Also, bacteria have been seen thriving in the most hostile environments you can imagine here on Earth. This greatly enhances the probability that among the hundreds of solar systems that we will no doubt discover and map in the next 25 years, there will be planets or their moons which will harbor at least bacteria. Anything more complex may be a problem. Earth itself was covered by bacterial life for its first 3 billion years, and only recently in the last 600 million years did multi-cellular plants and animals emerge.
To keep up to date on the searches for new planets, visit the Extrasolar Planets Encyclopedia
Copyright 1997 Dr. Sten Odenwald
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