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A search for habitable planets

Kepler, a NASA Discovery mission, is a spaceborne telescope designed to look for Earth-like planets around stars beyond our solar system.

"The Kepler Mission will, for the first time, enable humans to search our galaxy for Earth-size or even smaller planets," said principal investigator William Borucki of NASA's Ames research Center, Moffett Field,

California. "With this cutting-edge capability, Kepler may help us answer one of the most enduring questions humans have asked throughout history: Are there others like us in the universe?"

Kepler will detect planets indirectly, using the "transit" method. A transit occurs each time a planet crosses the line-of-sight between the planet's parent star that it is orbiting and the observer. When this happens, the planet blocks some of the light from its star, resulting in a periodic dimming. This periodic signature is used to detect the planet and to determine its size and its orbit.

Three transits of a star, all with a consistent period, brightness change and duration, provide a robust method of detection and planet confirmation. The measured orbit of the planet and the known properties of the parent star are used to determine if each planet discovered is in the habitable zone; that is, at the distance from its star where liquid water could exist on the surface of the planet.

The industrial partner for development of the hardware is Ball Aerospace & Technologies Corp., based in Boulder, Colorado. The mission is managed by NASA's Jet Propulsion Laboratory.

Scheduled to launch in 2007, Kepler will hunt for planets using a specialized one-meter diameter telescope called a photometer to measure the small changes in brightness caused by the transits.

The key technology at the heart of the photometer is a set of charged coupled devices (CCDs) that measures the brightness of hundreds of thousands of stars at the same time. CCDs are the silicon light-sensitive chips that are used in today's TV cameras, camcorders and digital cameras. Kepler must monitor many thousands of stars simultaneously, since the chance of any one planet being aligned along the line-of-sight is only about 1/2 of a percent.

Over a four-year period, Kepler will continuously view an amount of sky about equal to the size of a human hand held at arm's length or about equal in area to two "scoops" of the sky made with the Big Dipper constellation. In comparison, the Hubble Space Telescope can view only the amount of sky equal to a grain of sand held at arms length, and then only for about a half-hour at a time.

NASA selected Kepler as one of two Discovery missions from 26 proposals made in early 2001. The missions must stay within the Discovery Program's development cost cap of about $299 million. The Discovery Program emphasizes lower-cost, highly focused scientific missions.

Kepler will detect planets indirectly, using the "transit" method. A transit occurs each time a planet crosses the line-of-sight between the planet's parent star that it is orbiting and the observer. When this happens, the planet blocks some of the light from its star, resulting in a periodic dimming. This periodic signature is used to detect the planet and to determine its size and its orbit.

Which makes me question this whole "25% of stars have planets" thing. In order to detect an alleged planet, the planet has to pass between us and the remote star - that is, transit across the face of the star from our point of view. Now, think about that. What if we're not aligned with the ecliptic of that system. We'd never even see a single planet yet the system may have many.

And searching for rhythmic flickers in remote stars is far less glamorous than some of these articles try to make it sound in our "search for habitable planets".

Man, I must be in a bad mood or something. I love science and astronomy - I guess I just hate the hype sometimes.

Future Missions to Search for Earth-like Planets (cont.)

Darwin mission The European Space Agency has targeted the InfraRed Space Interferometer-Darwin for a launch in 2015 or later. Decisions about whether to go forward with the mission are expected around 2003.

The telescope, using infrared rather than optical wavelengths, would hunt for Earth-like planets around some 300 Sun-like stars within 50 light-years of Earth. Darwin would actually be an array of six small eyes, forming an effective giant that would mimic a 100-yard (91-meter) telescope.

Scientists are still studying how such a system might be designed.

Unlike current space-based telescopes, Darwin would operate somewhere between Mars and Jupiter, rather than in Earth orbit. This would allow the instruments to avoid the dust between Earth and Mars that obscures the view.

The six individual telescopes would be joined either by long arms or would each be mounted on individual spacecraft. In the former case, the rigid structure would rotate to build up the image. In the latter case, the individual spacecraft would have their own rocket motors and dance around each other to build up the image.

...Kepler, a NASA Discovery mission, is a spaceborne telescope.....

Wow! Thanks for this excellent bit of info.

Eat your heart out Disney trashed Discovery magazine.