Search For More Planets Intensifies
Just one year ago this month, astronomers announced the discovery of the first planet circling a sunlike star outside our solar system. Now the count of alien planets is up to 10 - surpassing the eight others in our own back yard - and rising fast.
“It’s sort of the Planet-of-the-Month Club,” joked George Gatewood, a planet hunter at the University of Pittsburgh’s Allegheny Observatory.
So far, none of the newly detected heavenly bodies - giant gas balls similar to Jupiter and Saturn - resembles the Earth or is likely to harbor life.
And so far, none of them has been observed directly. Rather, their presence has been inferred from tiny fluctuations, or wobbles, that an invisible companion causes in the motion of a star.
Nevertheless, multiple observations by at least five separate teams of astronomers greatly increase the probability that Earthlike planets will be found elsewhere in our galaxy in the next decade or two.
The Clinton administration and the National Aeronautics and Space Administration have made the search for extraterrestrial life one of their highest priorities. A series of robotic expeditions to Mars, checking for signs of life on that nearby planet, will start next month.
“The extraordinary discovery” of these planets “has completely transformed the field of extra-solar planet detection,” said Alan Boss, an astrophysicist at the Carnegie Institution of Washington.
According to Boss, two stars - one in the Big Dipper and the other in the constellation Cancer (the Crab) - are believed to have “planetary systems” of two or more orbiting objects. This has created “tremendous hope among astronomers that planetary systems similar to ours do indeed exist,” Boss said.
Another star in the Big Dipper, a part of Ursa Major, has one planet circling around it. And other stars believed to be host to at least one giant planet are located in the constellations Andromeda, Bootes, Cygnus, Pegasus and Virgo.
As more powerful telescopes come into use, scientists hope to find smaller planets.
Some of the planets found so far are of a size and temperature that would permit them to harbor water, clouds and complex organic molecules, according to Geoffrey Marcy, a leading planet hunter at San Francisco State University.
In addition to the 10 planets circling around sunlike stars, astronomers have identified four other planets orbiting neutron stars - known as pulsars - in the constellation Virgo. Three planets were discovered around one pulsar and one around a second pulsar.
Pulsars are former stars that have exploded and collapsed into extremely dense, fast-spinning, highly radioactive neutron stars. Because of the intense radiation, life there is out of the question.
“You’d need a lead umbrella at the beach,” said Alexander Wolszczan, the Pennsylvania State University astronomer who discovered the pulsar planets four years ago.