The water abundance in a planetary atmosphere provides a key constraint on the planet's primordial origins because water ice is expected to play an important role in the core accretion model of planet formation. However, the water content of the Solar System giant planets is not well known because water is sequestered in clouds deep in their atmospheres. By contrast, short-period exoplanets have such high temperatures that their atmospheres have water in the gas phase, making it possible to measure the water abundance for these objects. We present a precise determination of the water abundance in the atmosphere of the 2 MJup short-period exoplanet WASP-43b based on thermal emission and transmission spectroscopy measurements obtained with the Hubble Space Telescope. We find the water content is consistent with the value expected in a solar composition gas at planetary temperatures (0.4-3.5x solar at 1 σ confidence). The metallicity of WASP-43b's atmosphere suggested by this result extends the trend observed in the Solar System of lower metal enrichment for higher planet masses.
@article{arxiv.1410.2255,
title = {A Precise Water Abundance Measurement for the Hot Jupiter WASP-43b},
author = {Laura Kreidberg and Jacob L. Bean and Jean-Michel Désert and Michael R. Line and Jonathan J. Fortney and Nikku Madhusudhan and Kevin B. Stevenson and Adam P. Showman and David Charbonneau and Peter R. McCullough and Sara Seager and Adam Burrows and Gregory W. Henry and Michael Williamson and Tiffany Kataria and Derek Homeier},
journal= {arXiv preprint arXiv:1410.2255},
year = {2014}
}
Comments
Accepted to ApJL; this version contains three supplemental figures that are not included in the published paper. See also our companion paper "Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy" by Stevenson et al