Astronomers nail down details of 'next-door' exoplanet

A University of California astronomer has measured the size and mass of an exoplanet located almost next door to us by astronomical standards, the school says. Diana Dragomir, a postdoctoral astronomer at UC Santa Barbara, has made the measurement of a "super-Earth" orbiting the star HD 97658 just 70 light years from Earth, the university reported Monday. A super-Earth is an exoplanet with a mass and radius between those of the Earth and Neptune, although the name refers to the planet's mass and does not imply similar temperature, composition, or environment to Earth. Dragomir examined data on the transits of the exoplanet HD 97658b -- the change in brightness of its host star as the planet passed in front of it -- gathered by a Canadian space telescope to improve measurements of its size and mass. "Measuring an exoplanet's size and mass leads to a determination of its density, which in turn allows astronomers to say something about its composition," she said. "Measuring the properties of super-Earths in particular tells us whether they are mainly rocky, water-rich, mini gas giants, or something entirely different." While the density of HD 97658b suggests it has a strong enough gravity to hold on to a thick atmosphere, it is unlikely to be capable of supporting any life as it is too close to its star to be in the habitable zone where liquid water ocean might exist, Dragomir and her co-researcher Jason Eastman said. "This discovery adds to the still small sample of transiting super-Earths around bright stars," said Dragomir, calling the study a "part of the progression toward understanding what exoplanets in the habitable zone might be like."