Over the past several years, NASA’s Kepler mission has discovered over a thousand confirmed planets with thousands more unconfirmed candidates awaiting follow up observations and even more planetary finds still being teased out of Kepler’s ever-growing data set. While Kepler data are able to provide information on the orbit and radius of its finds, the mass for only a small number of these extrasolar planets has been determined or are likely to be determined with the current generation of instruments. While astronomers continue to struggle to measure the masses of thousands of individual extrasolar planets found by Kepler, there have been efforts to derive a mass-radius relationship for extrasolar planets so that the mass of a planet with a known radius can at least be estimated. Even probable masses would be of value to scientists wishing to use Kepler’s radius and orbit data in statistical studies of planetary properties, dynamics, formation and evolution.
My latest essay for Centauri Dreams, entitled “A Mass-Radius Relationship for “Sub-Neptunes”’, reviews the recent work by Angie Wolfgang (University of California – Santa Cruz), Leslie A. Rogers (California Institute of Technology), and Eric B. Ford (Pennsylvania State University) to derive a mass-radius relationship for planets smaller than Neptune. This size range includes Earth-size planets as well as larger worlds like super-Earths and mini-Neptunes for which have no analogs in our solar system but have turned out to be quite common in other planetary systems.
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Related Reading
“Habitable Planet Reality Check: Terrestrial Planet Size Limit”, Drew Ex Machina, July 24, 2014 [Post]
“The Composition of Super-Earths”, Drew Ex Machina, January 3, 2015 [Post]
“The Transition from Rocky to Non-Rocky Planets”, Centauri Dreams, November 14, 2014 [Post]