Title: The Kepler-10 planetary system revisited by HARPS-N: A hot rocky world and a solid Neptune-mass planet Author: Xavier Dumusque, Aldo S. Bonomo, Raphaelle D. Haywood, Luca Malavolta, Damien Segransan, Lars A. Buchhave, Andrew Collier Cameron, David W. Latham, Emilio Molinari, Francesco Pepe, Stephane Udry, David Charbonneau, Rosario Cosentino, Courtney D. Dressing, Pedro Figueira, Aldo F. M. Fiorenzano, Sara Gettel, Avet Harutyunyan, Keith Horne, Mercedes Lopez-Morales, Christophe Lovis, Michel Mayor, Giusi Micela, Fatemeh Motalebi, Valerio Nascimbeni, David F. Phillips, Giampaolo Piotto, Don Pollacco, Didier Queloz, Ken Rice, Dimitar Sasselov, Alessandro Sozzetti, Andrew Szentgyorgyi, Chris Watson
Kepler-10b was the first rocky planet detected by the Kepler satellite and confirmed with radial velocity follow-up observations from Keck-HIRES. The mass of the planet was measured with a precision of around 30%, which was insufficient to constrain models of its internal structure and composition in detail. In addition to Kepler-10b, a second planet transiting the same star with a period of 45 days was statistically validated, but the radial velocities were only good enough to set an upper limit of 20 earth masses for the mass of Kepler-10c. To improve the precision on the mass for planet b, the HARPS-N Collaboration decided to observe Kepler-10 intensively with the HARPS-N spectrograph on the Telescopio Nazionale Galileo on La Palma. In total, 148 high-quality radial-velocity measurements were obtained over two observing seasons. These new data allow us to improve the precision of the mass determination for Kepler-10b to 15%. With a mass of 3.33 +/- 0.49 earth masses and an updated radius of 1.47 +0.03 -0.02 earth radii, Kepler-10b has a density of 5.8 +/- 0.8 g cm-3, very close to the value -0.02 predicted by models with the same internal structure and composition as the Earth. We were also able to determine a mass for the 45-day period planet Kepler-10c, with an even better precision of 11%. With a mass of 17.2 +/- 1.9 earth masses and radius of 2.35 +0.09 -0.04 earth radii, -0.04 Kepler-10c has a density of 7.1 +/- 1.0 g cm-3. Kepler-10c appears to be the first strong evidence of a class of more massive solid planets with longer orbital periods.
There is a new class of planet out there that astronomers are calling the "mega-Earth". It is an object with a hard surface like our own world but much, much bigger. The necessity for the new designation follows the discovery of a planet which has a mass some 17 times that of Earth. Read more
Astronomers Find a New Type of Planet: The "Mega-Earth"
Astronomers announced today that they have discovered a new type of planet - a rocky world weighing 17 times as much as Earth. Theorists believed such a world couldn't form because anything so hefty would grab hydrogen gas as it grew and become a Jupiter-like gas giant. This planet, though, is all solids and much bigger than previously discovered "super-Earths," making it a "mega-Earth." Read more