HAT-P-26b: A Neptune-mass exoplanet with a well-constrained heavy element abundance

Hannah R Wakeford; David K Sing; Tiffany Kataria; Drake Deming; Nikolay Nikolov; Eric D Lopez; Pascal Tremblin; David S Amundsen; Nikole K Lewis; Avi M Mandell; Jonathan J Fortney; Heather Knutson; Björn Benneke; Thomas M Evans

doi:10.1126/science.aah4668

HAT-P-26b: A Neptune-mass exoplanet with a well-constrained heavy element abundance

Science. 2017 May 12;356(6338):628-631. doi: 10.1126/science.aah4668.

Authors

Hannah R Wakeford¹, David K Sing², Tiffany Kataria³, Drake Deming⁴, Nikolay Nikolov², Eric D Lopez^{5

6}, Pascal Tremblin⁷, David S Amundsen^{8

9}, Nikole K Lewis¹⁰, Avi M Mandell⁵, Jonathan J Fortney¹¹, Heather Knutson¹², Björn Benneke¹², Thomas M Evans²

Affiliations

¹ NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA. hannah.wakeford@nasa.gov.
² Astrophysics Group, University of Exeter, Physics Building, Stocker Road, Exeter, Devon, EX4 4QL UK.
³ NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109, USA.
⁴ Department of Astronomy, University of Maryland, College Park, MD 20742, USA.
⁵ NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA.
⁶ Institute for Astronomy, Royal Observatory Edinburgh, University of Edinburgh, Blackford Hill, Edinburgh, UK.
⁷ Maison de la Simulation, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), CNRS, Université Paris-Sud, Université Versailles Saint-Quentin-en-Yvelines (UVSQ), Université Paris-Saclay, 91191 Gif-sur-Yvette, France.
⁸ Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10025, USA.
⁹ NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA.
¹⁰ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA.
¹¹ Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA.
¹² Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.

PMID: 28495748
DOI: 10.1126/science.aah4668

Abstract

A correlation between giant-planet mass and atmospheric heavy elemental abundance was first noted in the past century from observations of planets in our own Solar System and has served as a cornerstone of planet-formation theory. Using data from the Hubble and Spitzer Space Telescopes from 0.5 to 5 micrometers, we conducted a detailed atmospheric study of the transiting Neptune-mass exoplanet HAT-P-26b. We detected prominent H₂O absorption bands with a maximum base-to-peak amplitude of 525 parts per million in the transmission spectrum. Using the water abundance as a proxy for metallicity, we measured HAT-P-26b's atmospheric heavy element content ([Formula: see text] times solar). This likely indicates that HAT-P-26b's atmosphere is primordial and obtained its gaseous envelope late in its disk lifetime, with little contamination from metal-rich planetesimals.

Publication types

Research Support, Non-U.S. Gov't