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BD+20594b is a Neptune-Sized Mega-Earth

30 Jan 2016, 10:00 UTC
BD+20594b is a Neptune-Sized Mega-Earth
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Espinoza et al. (2016) present the discovery of BD+20594b, a Neptune-sized mega-Earth in orbit around a Sun-like star with ~96 percent the mass, ~93 percent the size and ~88 percent the luminosity of the Sun. The planet’s density is measured to be high enough for it to be consistant with a pure rock composition. BD+20594b circles its host star every 41.7 days. It was first detected by NASA’s K2 mission, which looks for planets that transit their host stars. The amount of light BD+20594b blocks when it transits its host star indicates that it is ~2.23 times the size of Earth.Figure 1: Artist’s impression of a rocky planet.Subsequent high precision radial velocity measurements obtained from the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph on the 3.6 m telescope at La Silla Observatory in Chile show that gravitational perturbations from BD+20594b causes its host star to wobble by ~3.1 m/s. This allows the mass of BD+20594b to be estimated at ~16.3 times the mass of Earth. With both the size and mass known, the density of BD+20594b is found to be ~7.89 g/cm³. For comparison, the mean density of Earth is 5.514 g/cm³. Such a high density indicates that BD+20594b ...

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