Since 2007, when the first planet was discovered outside the thin disk of our Milky Way, astronomers have raced to locate a planet that looks and acts like Earth. This spring, they found a Jupiter-sized exoplanet (one outside our solar system) that French scientists predict will become an astronomical Rosetta stone.
Detected nearly 1,500 light-years away in the constellation Serpens Cauda, this exoplanet takes 95 Earth days to hurtle around its star at an orbital distance resembling Mercury’s. Named after the French-operated satellite COROT (Convection, Rotation, and Planetary Transit), CoRoT-9b’s atmosphere, with temperatures ranging from -9 to 314 degrees F, is what makes it like our own planet. Liquid water could exist there.
Many exoplanets orbit so close to their suns that they are difficult to distinguish from the host star’s glaring light. In the eight hours it took CoRoT-9b to cross, or transit, in front of its sun, however, astronomers were able to measure the attendant drop in the sun’s brightness to determine the planet’s size, trajectory, and composition. This gas giant is composed mostly of helium and hydrogen and may have a rocky core. About 400 exoplanets have been found so far, though in recent years technology has increased the likelihood that smaller, more habitable celestial bodies will be found.
Most promising is NASA’s Kepler satellite, launched in 2009 and outfitted with more than 40 cameras that can measure the brightness of 150,000 stars and store the data every six seconds. “No one has ever built a [space-based] instrument with this kind of precision,” says William Borucki of the Kepler team. With five exoplanets under its belt already, who knows what Kepler will discern in the cosmos or what it will reveal about the nature of our own existence.
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