Not Just Nine: The Search for New Worlds
Artist's conception of
an extrasolar planet
Courtesy of NASA
As of November, 2003, 119 planets have been discovered outside our Solar System, with more being found each year. While most of these are gas giants, inimical to life as we know it, the search goes on for Earth-like planets where environmental conditions might exist to foster extra-terrestrial life. Where once it seemed that that we were perhaps alone in the universe, some astronomers now speculate that planets are far from rare, and may even be the norm for suns like ours.
Both NASA and the European Space Agency have embarked on quests to find planets outside our solar system (known as extrasolar or exosolar planets) and to analyze their atmospheres in search of the three gases that might indicate the presence of life: carbon dioxide, water vapor and ozone.
Image of the star
Upsilon Andromedae,
circled by three
unseen planets
Courtesy of NASA
The search for new planets is not an easy one. From our own Solar System we see breathtaking pictures of the surface of Mars, the rings of Saturn and the bands of Jupiter. But there are no images of these faraway planets. They are not lost in the darkness of space, but in the brilliance of stars. Current detection methods cannot at present distinguish the weak visual light reflected from these distant planets from the much greater light of the stars that they circle.
How can a planet be discovered if it can't be directly observed? The detection of new worlds does not at present involve observation of the planets themselves, but of the effect that the planets have on their stars. When a planet orbits a star, its gravity causes the star to wobble slightly. Across the vast distances of space, this wobble is so minute that NASA has likened its measurement to measuring the movement of an astronaut's finger from Earth. Because their gravitational effects are greater, so far only large extrasolar planets have been found.
NASA hopes that its effort to find new worlds, known as "The Origins Project" will change this.
Photo of Keck
Interferometer
Courtesy of NASA/
JPL/Caltech
Some elements of the Project are already in place: perched atop a volcano in Hawaii, the 8-story high twin telescopes of the Keck Interferometer are currently probing distant galaxies. In the future, an instrument called an interferometer will combine light gathered by these telescopes and from several other smaller telescopes to perhaps create the first images extrasolar planets.
The largest single-mount telescope in the world, The Large Binocular Telescope, now nearing completion in Arizona, will not only be capable of taking high resolution photographs of distant objects, it will also study the dust clouds surrounding stars that obscure the visibility of planets in an effort to assist other planetary discovery missions.
Kepler, a space telescope set to launch in 2007, will take a different approach to the discovery of planets. When a planet crosses between the star that it orbits and the telescope, a minute amount of light from the star is blocked. Kepler will measure the tiny differences in the stars brightness, calculating the size of the planet, and by studying the frequency of the dimming of light, will also determine the planet's orbit.
Also space-based, The Space Interferometry Mission, will launch in 2009 and should be able to detect the wobble that even small, Earth-like planets have on their stars.
Artist's conception of
the Terrestrial Planet
Finder
Courtesy of NASA/
JPL/Caltech
Finally, should these other efforts indicate that Earth-like planets are common around suns like ours, the Terrestrial Planet Finder, far powerful than the Hubble telescope, will be launched between 2012-2015 to focus on the detection and analysis of nearby Earth-like planets, searching for signs of conditions that might foster life, or for the markers of life itself.
Hopefully within the next few years, one entry into the ever-growing catalog of distant planets will have the tell-tale stamp of life and the question at the center of the quest: "Are we alone?" can be answered: "Probably not".
