Washington: Astronomers have discovered a planet not much more than twice Earth`s diameter and a little less than eight times its mass, about 70 light-years from our world.
HD 97658b is a super-Earth, a class of planet for which there is no example in our home solar system.
While the discovery of this particular exoplanet is not new, determining its true size and mass is, thanks to Diana Dragomir, a postdoctoral astronomer with UC Santa Barbara`s Las Cumbres Observatory Global Telescope (LCOGT).
As part of her research, Dragomir looked for transits of this exoplanet with Canada`s Microvariability and Oscillations of Stars (MOST) space telescope.
The telescope was launched in 2003 to a pole-over-pole orbit about 510 miles high.
Dragomir analyzed the data using code written by LCOGT postdoctoral fellow Jason Eastman.
The average density of HD 97658b is about four grams per cubic centimeter, a third of the density of lead but denser than most rocks.
Astronomers see great significance in that value-about 70 percent of the average density of Earth-since the surface gravity of HD 97658b could hold onto a thick atmosphere.
But there`s unlikely to be alien life breathing those gases.
The planet orbits its sun every 9.5 days, at a distance a dozen times closer than we are from our Sun, which is too close to be in the habitable zone, nicknamed the Goldilocks zone.
The Goldilocks nickname is apropos: If a planet is too close to its star, it`s too hot; if it`s too far away, it`s too cold, but if it`s in the zone, it`s "just right" for liquid water oceans, one condition that was necessary for life here on Earth.
HD 97658b orbits its star at a distance farther than many of the currently known exoplanet s.
HD 97658b is only the second super-Earth known to transit a very bright star.
The findings are published online in the Astrophysical Journal Letters.