Two new alien worlds somewhat larger than Earth have been found circling a nearby star.
These exoplanets (or extrasolar planets – planets circling a star other than our own), HD 7924c and HD 7924d, are “super Earths”, 7.9 and 6.4 times greater than our home planet, researchers said. They orbit the start HD 7924 – hence their names – which is just 54 light years from the sun. Pretty darn close when you consider the Milky Way is about 100,000 light years across.
With this discovery, scientists now know three planets in the HD 7924 system. Another super Earth HD 7924b was discovered in 2009. All three planets lie closer to their host star than Mercury does to the sun. They complete their orbit in five, 15 and 24 days, respectively.
“The three planets are unlike anything in our solar system, with masses seven to eight times the mass of Earth and orbits that take them very close to their host star,” study co-author Lauren Weiss, a graduate student at the University of California, Berkeley, said in a statement.
According to CBS News, the research team, led by University of Hawaii (UH) graduate student BJ Fulton, used the combined observations of three ground-based telescopes to detect tiny wobbles in the star HD 7924 caused by the gravitational pull of the two newfound planets, and then to verify the worlds’ existence.
Astronomers first found planets orbiting another star in 1992, and the exoplanet tally has now risen to nearly 2,000. More than half of these alien worlds have been discovered by NASA’s Kepler space telescope, which launched in March 2009.