YET NOT ANOTHER EARTH MAP PATCH

It makes wide-field pictures every 30 minutes, capturing the light of more than 100,000 stars in a single patch of sky between the bright stars Deneb and Vega. 95-meter aperture and a 95-megapixel detector. Launched from Cape Canaveral last March, KepВler is essentially just a big digital camera with a. The United States' Kepler satellite is COROT's more ambitious successor. The French COROT satellite, now in the third and final year of its prime mission, has discovered seven transiting exoplanets, one of which is only 70 percent larger than Earth. At most a tenth of all planetary systems are likely to be oriented so that these mini-eclipses, called transits, are visible from Earth, which means that astronomers may have to monitor many stars patiently to capture just a few transits. The Earth tugs the sun around at only one-tenth walking speed, or about the rate that an infant can crawl astronomers cannot yet prize out so tiny a signal from the light of a distant star.ДЄnother approach is to watch a star for the slight periodic dip in its brightness that will occur should an orbiting planet circle in front of it and block a fraction of its light. That's sufficient to detect a giant planet in a big orbit, or a small one if it's very close to its star, but not an Earth at anything like our Earth's 93-million-mile distance from its star. In recent years astronomers have refined the Doppler technique so exquisitely that they can now tell when a star is pulled from its appointed rounds by only one meter a second-about human walking speed. Most of the others have been detected by using the spectroscopic Doppler technique, in which starlight is analyzed for evidence that the star is being tugged ever so slightly back and forth by the gravitational pull of its planets. Only 11 exoplanets, all of them big and bright and conveniently far away from their stars, have as yet had their pictures taken. Yet by pushing technology to the limits, astronomers are rapidly approaching the day when they can find another Earth and interrogate it for signs of life. To see a planet as small and dim as ours amid the glare of its star is like trying to see a firefly in a fireworks display to detect its gravitational influence on the star is like listening for a cricket in a tornado. No planets quite like our own have yet been found, presumably because they're inconspicuous. Three benighted planets have been found orbiting a pulsar-the remains of a once mighty star shrunk into a spinning atomic nucleus the size of a city-while untold numbers of worlds have evidently fallen into their suns or been flung out of their systems to become вЂњfloatersвЂќ that wander in eternal darkness.ДЄmid such exotica, scientists are eager for a hint of the familiar: planets resembling Earth, orbiting their stars at just the right distance-neither too hot nor too cold-to support life as we know it. Circling another star 150 light-years out is a scorched вЂњhot Jupiter,вЂќ whose upper atmosphere is being blasted off to form a gigantic, comet-like tail. HaldaneвЂ™s famous remark that вЂњthe universe is not only queerer than we suppose, but queerer than we can suppose.вЂќ ThereвЂ™s an Icarus-like вЂњhot SaturnвЂќ 260 light-years from Earth, whirling around its parent star so rapidly that a year there lasts less than three days. Many are so strange as to confirm the biologist J. To date, astronomers have identified more than 370 вЂњexoplanets,вЂќ worlds orbiting stars other than the sun. It took humans thousands of years to explore our own planet and centuries to comprehend our neighboring planets, but nowadays new worlds are being discovered every week. This story appears in the December 2009 issue of National Geographic magazine.

Yet not another earth map