WASHINGTON — It’s boom time for planet hunters. Astronomers are bagging new worlds at an average rate of more than two a month. As of July 20, the latest available date, 246 extrasolar planets had been detected circling other stars in the Milky Way galaxy. Among them are 25 alien ‘solar systems’ consisting of two, three or four bodies orbiting single suns. Four new exoplanets, as they’re also called, were reported just this month; three were reported in May and 28 during the last 12 months. The smallest known exoplanet, only twice as wide and five times heavier than Earth, was revealed in April. ‘Ten years ago, we knew of no extrasolar planets,’ said John Bally, an astronomer at the University of Colorado in Boulder. ‘Now we’re discovering planets almost weekly.’ ‘Extrasolar planets are everywhere in the sky,’ said Sylvain Korzennik, a researcher at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. In addition to simply boosting the count of planets, new technologies are letting scientists begin to analyze the chemical makeup of their finds. Water molecules have been spotted in the atmosphere of at least one new planet. The fingerprints of elements such as […]