Puffed-up Atmosphere of a Star-hugging Gas Giant Planet

This artist's illustration shows an extrasolar planet orbiting very close to its host star. The planet designated HD 209458b, is about the size of Jupiter. Unlike Jupiter, the planet is so hot that its atmosphere is "puffed up." Starlight is heating the planet's atmosphere, causing hot gas to escape into space, like steam rising from a boiler.

HD 209458b completes an orbit every 3.5 days. The Hubble Space Telescope could not image the planet directly because it is too close to the star. Astronomers used Hubble to analyze the starlight that filtered through the planet's atmosphere. Imprinted on the starlight is information about the atmosphere's structure and chemical makeup.

About the data

The Hubble image was created from HST data from proposal 10145 : A. Vidal-Madjar, A. Lecavelier des Etangs, and J.-M. Desert (CNRS, Institute d'Astrophysique de Paris), G. Ballester (University of Arizona), J. Walsh (Space Telescope - European Coordinating Facility), D. Ehrenreich, G. Hebrard, and R. Ferlet (CNRS, Institute d'Astrophysique de Paris), J. Mcconnell (York University), M. Mayor (Observatoire de Geneve), C. Parkinson (California Institute of Technology); and proposal 9447: D. Charbonneau (Harvard University), J.-L. Bertaux (Service d'Aeronomie du Centre National de la Recherche Scientifique), T. Brown (University Corporation for Atmospheric Research), R. Gilliland (STScI), and R. Noyes (Harvard-Smithsonian Center for Astrophysics).

The science team comprises: G. Ballester (University of Arizona), D. Sing (University of Arizona/Institute d'Astrophysique de Paris), and F. Herbert (Institute d'Astrophysique de Paris).