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

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 Object

  • R.A. Position
    R.A. PositionRight ascension – analogous to longitude – is one component of an object's position.
    22h 03m 10s.80
  • Dec. Position
    Dec. PositionDeclination – analogous to latitude – is one component of an object's position.
    +18° 53' 4".0
  • Constellation
    ConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.
    Pegasus
  • Distance
    DistanceThe physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.
    Approximately 150 light-years (46 parsecs)

About the Data

  • Data Description
    Data DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
    Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.
    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).
  • Instrument
    InstrumentThe science instrument used to produce the data.
    HST>STIS, HST>ACS/HRC, and HST>ACS/SBC
  • Exposure Dates
    Exposure DatesThe date(s) that the telescope made its observations and the total exposure time.
    May - July, 2003 (STIS) and May - July, 2005 (ACS)
  • Filters
    FiltersThe camera filters that were used in the science observations.
    STIS: G430L, G750L ACS: PR110L, PR200L, F115LP, F220W, F344N, F250W, and F330W
  • Object Name
    Object NameA name or catalog number that astronomers use to identify an astronomical object.
    HD 209458b
  • Object Description
    Object DescriptionThe type of astronomical object.
    Extrasolar Planet
  • Release Date
    January 31, 2007
  • Science Release
    Hubble Probes Layer-cake Structure of Alien World’s Atmosphere
  • Credit
    NASA, ESA, and G. Bacon (STScI)

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Details

Last Updated
Mar 28, 2025
Contact
Media

Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov