Hot and heavy ‘super Earths’

Planet hunters are having a field day. This week, astronomers announced the discovery of three so-called “super Earths” orbiting a star some 42 light years away. Super Earths are planets with masses less than Neptune’s but greater than Earth’s.

The planets are hanging tight with their host star, a burning gas ball with a bit less heft than the sun. Whereas Mercury orbits the sun once every 88 days, the largest and outermost of the three super Earths – which tips the scales at 9.4 times Earth’s mass – orbits its star once every 20.4 days. The team, led by Geneva Observatory astronomer Michel Mayor, says it has identified as many as 45 super Earth candidates with masses 30 times greater than Earth’s and with orbits quicker than 50 days.

And stand by for more as new technologies come on line. The spectrograph Dr. Mayor’s team used at the European Southern Observatory’s La Silla Observatory in Chile can detect potential planets from 2 to 10 times Earth’s mass. Right now, anything smaller is too tiny to detect. Researchers at Harvard University plan to test a new device next month dubbed the astrocomb. If all works well, it should be able to spot truly Earth-size planets. Initial tests are set for next month at the Whipple Observatory on Mt. Hopkins in Arizona, according to Ronald Walsworth, a senior physicist at the Harvard-Smithsonian Center for Astrophysics, in Cambridge, Mass. The high-precision spectrograph will be used in tandem with the US Kepler spacecraft, set for launch in February. Data from the two methods are expected to discover Earth-size planets that fall within the habitable zone.