期刊
ASTROPHYSICAL JOURNAL
卷 747, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/747/1/35
关键词
eclipses; planets and satellites: atmospheres; planets and satellites: individual (GJ1214b); stars: low-mass; techniques: spectroscopic
资金
- NASA [HST-GO-12251, NAS 5-26555]
- David and Lucile Packard Fellowship for Science and Engineering
- National Science Foundation [AST-0807690]
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1004488] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [0807690, 1109468] Funding Source: National Science Foundation
Capitalizing on the observational advantage offered by its tiny M dwarf host, we present Hubble Space Telescope/Wide Field Camera 3 (WFC3) grism measurements of the transmission spectrum of the super-Earth exoplanet GJ1214b. These are the first published WFC3 observations of a transiting exoplanet atmosphere. After correcting for a ramp-like instrumental systematic, we achieve nearly photon-limited precision in these observations, finding the transmission spectrum of GJ1214b to be flat between 1.1 and 1.7 mu m. Inconsistent with a cloud-free solar composition atmosphere at 8.2 sigma, the measured achromatic transit depth most likely implies a large mean molecular weight for GJ1214b's outer envelope. A dense atmosphere rules out bulk compositions for GJ1214b that explain its large radius by the presence of a very low density gas layer surrounding the planet. High-altitude clouds can alternatively explain the flat transmission spectrum, but they would need to be optically thick up to 10 mbar or consist of particles with a range of sizes approaching 1 mu m in diameter.
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