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Discovered by the Transit Method in 2012, this “hot Uranus” orbits GJ 3470, an M1.5 Dwarf 82 light-years from Earth. It has recently yielded some interesting characteristics about its atmosphere in spectroscopic results from the new Keck/MOSFIRE spectrograph – MOSFIRE standing for Multi-Object Spectrometer For Infra-Red Exploration.


The current measurements are consistent with a flat transmission spectrum, suggesting the atmosphere could contain high-altitude cirrus clouds and haze, disequilibrium chemistry, unexpected abundance patterns, or a metal-rich atmosphere. GJ 3470b also has a low bulk density, so the mean molecular mass of the atmosphere must be less than 9. For perspective, the mean molecular mass of dry air on Earth is just under 29.


If the atmosphere of GJ 3470b turns out to be cloud-free, spectral features will be detectable with future observations. This particular study has also contributed to a better understanding of the steps necessary for well-calibrated MOSFIRE observations, providing advice for future surveillance with this instrument.


GJ 3470b is about 14 times as massive as Earth (.0441 the mass of Jupiter) but has a radius greater than 1/3 (.375) of Jupiter’s radius and orbits its host star every 3.34 days.

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