University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Friday, July 25th 2014
11:00 am:
Speaker: Andrew W. Howard, Institute for Astronomy, University of Hawaii - Manoa
Subject: Earth-sized Exoplanets

The Kepler Mission has taught us that Earth-sized planets in the Habitable Zones of Sun-like stars are common and that many Earth-sized planets have rocky compositions. Three recent results highlight these remarkable properties of Earth-sized planets. First, our team measured the mass of the planet Kepler-78b, the first Earth-sized planet with a measured mass and radius outside of the Solar System. The bulk density of 5 grams per cubic centimeter suggests a rocky composition with an insubstantial atmosphere, similar to Earth. In a separate project, we showed that high densities are common for small exoplanets. Planets smaller than about 1.5 times Earth-size are mostly rocky, while thick gas atmospheres envelop most larger planets. Finally, our team estimated that 22 percent of Sun-like stars have a planet that is 1-2 times the size of Earth orbiting in the Habitable Zone. Warm, Earth-sized planets appear to be common.

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