The Search for Extrasolar Planets
One of the biggest projects going on in space exploration today is the search for and discovery of planets orbiting other stars. These planets are what scientists refer to as extrasolar planets. At present, most of the planets that have been discovered are Jupiter-sized or larger but in the not too distant future or about 2012 the Terrestrial Planet Finder will be launched which will be capable of discovering many smaller planets or Earth-sized planets. When this happens, whole solar systems with many planets will be discovered. And with more planets being found, the more opportunities there will be for life in the universe.
The Discoveries
Extrasolar planets were thought by scientists for years to exist but it wasn't until October 6, 1995 that the first extrasolar planet was discovered to be orbiting a sun-like star 51 Pegasi in the constellation Pegasus. Since then, planets have been discovered orbiting such stars as 70 Virginis in the constellation Virgo, 47 Ursae Majoris in Ursa Major, 55 Cancri in Cancer, Tau Bootis in Bootes, 16 Cygni in Cygnus and many others. All told, 333 extrasolar planets have now been discovered to date.
In discovering extrasolar planets, one of the methods scientists use makes use of the fact that when a planet orbits a star , the planet's gravitational pull causes the star to wobble slightly. When the star wobbles toward the Earth, its lightwaves are shifted to the blue end of the light spectrum. When the star wobbles away from the Earth, its lightwaves are shifted toward the red end of the spectrum or red shifted. Scientists examine these differences in wavelengths and can thus determine the planet's size and orbital characteristics. This method is called the radial velocity method. Other methods are also being used in extrasolar planet detection such as astrometry which uses the precise measurement of a star as compared to the backround stars; the transit method which measures the periodic diming of a star caused by a planet passing in front of it; and then there is the direct detection method where scientists must cancel out the light of the target star to be able to detect the planet. As scientists improve their methods, to detect these extrasolar planets, many more will be discovered. The future for discovering new worlds certainly looks exciting.
For more information on extrasolar planets, visit these websites
1. California & Carnegie Planet Search
3. Giant Planets Orbiting Faraway Stars
6. Planet Quest
7. Planet Quest New Worlds Atlas
8. Planetary Systems and their Changing Theories
10. The Search for Extrasolar Planets
11. Tranitsearch.org