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Forming Graphite-Like Carbon in the Atmosphere of GJ 436b

16 Jul 2015, 23:00 UTC
Forming Graphite-Like Carbon in the Atmosphere of GJ 436b
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GJ 436b is a Neptune-sized planet that orbits around a relatively small M-dwarf star located only 33 light years away. The planet is ~10 times closer to its parent star than Mercury is to the Sun and it completes one orbit around its host star in just 2.64 days. Being so close to its parent star, the planet is referred to as a hot-Neptune and its dayside is heated to a temperature of ~800 K. GJ 436b is estimated to have 22 times the mass of Earth and 4.3 times the radius of Earth. A rocky core is predicted to exist at the center of GJ 436b. Surrounding the rocky core is a mantle of exotic high pressure water-ice. Finally, an envelope of hydrogen and helium gas forms the outermost layer of GJ 436b.By observing the thermal emission from the dayside of GJ 436b, Stevenson et al. (2010) found that the methane (CH4) to carbon monoxide (CO) ratio in the planet’s atmosphere is at least ~10,000 times smaller than predicted. This is puzzling because in a hydrogen-dominated atmosphere at the temperatures found on GJ 436b, carbon in the atmosphere should prefer CH4 over CO. A likely reason for the lower-than-expected ...

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