Finding extrasolar planets is quite difficult mainly because of three basic facts: planets don't produce any light of their own; they are far from us; and they are lost in the blinding glare of their parent stars. But now, NASA engineers have found a way to eliminate this blinding light, and this is "a giant step toward finding Earth-like planets." At Hawaii's Keck Observatory in Mauna Kea, they used the Interferometer, which links the observatory's two telescopes, and they blocked starlight by adding an instrument called a "nuller." For example, they reduced the blinding light of Vega by 100 times. This will help NASA to select targets for its future SIM PlanetQuest mission, scheduled to launch in 2011, and its two Terrestrial Planet Finder observatories, which should be launched in 2016 and 2019. Will NASA find life somewhere in the universe? Maybe not, but it will be easy to find other planets.
Here is the first paragraph of this NASA's new release.
Are we alone in the universe? Are there planets like Earth around other "suns" that might harbor life? Thanks to a recent technology breakthrough on a key NASA planet-finding project, the dream of answering those questions is no longer light-years away.
After this lyrical introduction, here are the facts.
On a crystal clear, star-filled night at Hawaii's Keck Observatory in Mauna Kea, NASA engineers successfully suppressed the blinding light of three stars, including the well-known Vega, by 100 times. This breakthrough will enable scientists to detect the dim dust disks around stars, where planets might be forming. Normally the disks are obscured by the glare of the starlight.
Engineers accomplished this challenging feat with the Keck Interferometer, which links the observatory's two 10-meter (33-feet) telescopes. By combining light from the telescopes, the Keck Interferometer has a resolving power equivalent to a football-field sized telescope. The "technological touchdown" of blocking starlight was achieved by adding an instrument called a "nuller."
Before going further, below are two small infrared images of Neptune obtained by the Palomar Observatory's Hale Telescope. From top to bottom, you'll see the improvement in resolution attained by using an adaptive optics system. (Credit: NASA). This is a different technique that the one used at Keck, but it will give you an idea of the improvements brought by imaging technologies.
For more details about NASA's planet-finding missions, please visit the PlanetQuest website. The technology used to eliminate most of the blinding starlights is described on these two pages about interferometry and planet imaging. Here is NASA's definition of interferometry.
An alternative way to get a picture of a distant planet is to replace one large mirror with a number of smaller mirrors and combining their light in a process called interferometry.
And here is a short explanation of the "nulling" technique.
Interferometers provide extremely good angular resolution. That means they are very good at sorting out which light waves come from which part of the star system. Additionally, an interferometer can be "tuned" so that the light coming from the exact center in the field of view (where the star is) will be blanked out or nulled, while the light from any other area will be viewed normally.
And what will this technique used for? Let's return to the NASA's news release.
This setup may eventually help scientists select targets for NASA's envisioned Terrestrial Planet Finder missions. The success of those potential future missions, one observing in visible light and one in infrared, depends on being able to find Earth-like planets in the dust rings around stars.
So far, scientists around the world have found 150 planets orbiting other stars. Most are giants, like Jupiter; none is as small as Earth. Scientists believe the best odds of finding life outside our solar system are on Earth-sized planets, particularly those with the right temperature, density and chemistry.
And while we'll have to wait for a decade or two before knowing the results of NASA's planet-finding missions, you can watch this short video (Quicktime format, 9.42 MB, 3'05") which "provides a dramatic, fast-paced introduction to NASA's search for life-bearing planets around other stars, featuring planet-hunter Geoff Marcy."
Sources: NASA's Jet Propulsion Laboratory, September 29, 2005; and NASA's PlanetQuest web site
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