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" In just the last fifteen years, scientists have found more than 300 extrasolar planets, and every month brings more. This past November the Hubble Space Telescope captured the first visible-light image of a planet orbiting another star--weeks after, the ground-based Keck and Gemini observatories scored another first when they captured three planets in infrared images. Still, none of these exoplanets are likely to harbor life--most are huge Jupiter-like planets that are too hot or too cold. Small, rocky Earth-like worlds are dim and difficult to see directly--or indirectly, as faint gravitational wobbles--with existing telescopes. NASA&amp;#039;s KEPLER space telescope hopes to change all that. Named after Johannes Kepler, this new space telescope will be the first space telescope to use the most promising method we know of: transit photometry, measuring the change in brightness that occurs when a planet passes in front of its star. The technique can reveal the presence of a planet as well as its orbit and even its size.  &amp;quot;KEPLER is the first mission of its kind launched by NASA to be able to detect planets the size of the Earth, at distances from stars that are in the habitable zone where you could have liquid water,&amp;quot; explains Patricia Boyd, KEPLER program scientist at NASA headquarters. KEPLER will spend the next 3.5 years gazing simultaneously and continuously at 100,000 sunlike stars in the Cygnus region of the Milky Way, ever watchful for those faint dips in a star&amp;#039;s brightness. When they&amp;#039;re detected, and then confirmed by a second sighting that will prove a periodic orbit, other space- and ground-based observatories will train their eyes onto the candidate stars to confirm the findings and gather more information.  The heart of KEPLER is its photometer, capable of detecting changes in light of less than 84 parts per million and composed of 42 CCDs (charge-coupled devices). The array of dual-channel 2200 by 1024\u00C3pixel CCDs collects and processes light from a Schmidt telescope with an aperture of almost a full meter and a field of view about 12 degrees in diameter, much wider than the Hubble. &amp;quot;It&amp;#039;s the first time any photometer this large has been used in space, or probably anywhere,&amp;quot; Boyd says. &amp;quot;The real unique feature of KEPLER&amp;#039;s photometer is just the sheer size, the number of CCDs.&amp;quot; (Hubble only uses four.) The idea of detecting planets through transit photometry has been around for over thirty years, but only recently has technology made it a practical strategy for planet hunting. It&amp;#039;s been a personal quest for KEPLER principal investigator Bill Borucki. After years of rejected mission proposals, Borucki finally got KEPLER approved in December 2001, helped not only by the growing pace of extrasolar planetary discoveries but also by advances in CCD design. &amp;quot;I think we all recognized it was going to be a difficult slog and it certainly has been, but it&amp;#039;s worthwhile,&amp;quot; he says.  KEPLER&amp;#039;s results will also guide the design of more ambitious future missions such as the Terrestrial Planet Finder, but whatever its findings, they will have profound implications. &amp;quot;If, for example, Earthlike planets turn out to be very rare, in fact, if we don&amp;#039;t see them, then it really says something about the rarity of our own planet and how important it is to take care of it,&amp;quot; muses KEPLER chief engineer Riley Duran. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/space/telescopes/a6343/4307535/>