Earthlings have long been fascinated by the possibility. They are forever seeing UFOs in the night sky or in their own backyards, and reporting close encounters with Martians, alien abductors and a host of other out-of-thisworld creatures and things.
Over the years, these space beings have sprung to life in supermarket tabloids, science fiction novels, movies and TV showsemdash;in everything from War of the Worlds to Star Wars, Star Trek and The XFiles. Last week, they even popped up at a meeting of the American Astronomical Society in San Antonio, Tex., where two American scientists announced that they had found evidence of distant planets that might be capable of supporting life. “We watched Star Trek, and Jean-Luc Picard had no trouble finding planets, but we professionals did,” said Geoffrey Marcy, an astronomer based in Berkeley, Calif. “And now finally, there’s a site for Jean-Lucemdash; and for extraterrestrial life.”
Some scientists were more skeptical. For one thing, complex observations and calculations will be needed before the existence of the two new planets can be confirmed. As for there being life on either of them, says Karl Kamper, a University of Toronto astronomer, “it is far-fetched to speculate on that now.”
Still, the news from San Antonio was exhilarating because until recently there was scant evidence that planets existed anywhere in the universeemdash;except in the earth’s own solar system. Using a 120-inch telescope near San José, Calif., Marcy and another scientist, Paul Butler, began searching for other worlds in 1987. They did this by studying 120 distant stars and searching for telltale variations in light waves emitted by the stars that could be caused by the gravitational force of an orbiting planet. In the end, the scientists found two stars that they believe have orbiting planetsemdash;though these cannot be seen from earth.
In one case, they found evidence that a planet eight times larger than Jupiteremdash;the
solar system’s largest planetemdash;is probably orbiting a star called 70 Virginis. The planet could have a surface temperature of about 85 Cemdash;scorching by earth standards, but perhaps cool enough, said Marcy, to permit the emergence of life. Still, like g Jupiter, the planet would proba^ bly consist largely of gas and, if “ life existed there, it would more likely be on the planet’s moonsemdash;if it has any.
The second discoveryemdash;a suspected planet 3.5 times larger than Jupiter travelling in a wide orbit around the star 47 Ursae Majorisemdash;appeared likely to have an even less hospitable environment, with frigid surface temperature of about -80 C. (Temperatures on the planets were calculated on the basis of the amount of light emitted by the star, the planet’s distance from the star and other factors.) Butler speculated that the planet might be warmer in its lower atmosphere and added that because of the planet’s dis-
tance from its star, “this system is the closest thing that we’ve seen to anything like our own solar system.”
The Californians’ survey was not the first systematic search for planets elsewhere in the universe. Between 1980 and 1992, a team of Canadian scientists, using the Canada-France-Hawaii telescope at Mauna Kea, Hawaii, examined 21 starsemdash;and found nothing. “I feel more optimistic now that there really are other planets out there,” says Gordon Walker, a University of British Columbia astronomer who led the survey team at one stage. “But it shows that planets are something rare in the universeemdash;much rarer than we expected.”
How likely is it that planets elsewhere in the universe will be populated by living creatures? “It depends,” says Walker, “on how you define life. We don’t really know how life forms, and it’s important to remember that earth has a unique set of conditions. What kind of conditions might exist on gt; a planet with a temperature of 85 C, we really can’t say.” Alexander g Wolszczan, a Pennsylvania State I University astronomer who in
0 1992 reported evidence of planets
1 orbiting the core of a dead star, £ says that it is too soon to specult; late about life on planets whose I existence has yet to be proven. = “Given the likely surface tempera-
0 ture of these planets,” says Wol-
1 szczan, “it’s reasonable to think
that there might be water. And the next step is to think, well, there might be life. But I would be very skeptical about any extrapolations like that.” Ultimately, adds Wolszczan, “there is really no way to be sure what is out there until we can design a spaceship good enough to take us there.” As the next best thing, astronomers around the world will now begin aiming their telescopes at the sites of the Marcy-Butler discoveries, as the search continues for firm evidence of distant planets and signs of life.
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