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Artist’s Concept of Extasolar Planet GJ 436b
This artist's concept shows "The Behemoth," an enormous comet-like cloud of hydrogen bleeding off of a warm, Neptune-sized planet just 30 light-years from Earth. Also depicted is the parent star, which is a faint red dwarf named GJ 436. The hydrogen is evaporating from the planet due to extreme radiation from the star. A phenomenon this large has never before been seen around any exoplanet.
About the Object
- R.A. PositionR.A. PositionRight ascension – analogous to longitude – is one component of an object's position.11h 42m 11s.09
- Dec. PositionDec. PositionDeclination – analogous to latitude – is one component of an object's position.+26° 42' 23."65
- ConstellationConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.Leo
- DistanceDistanceThe 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.30 light-years (9.2 parsecs)
About the Data
- Data DescriptionData 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.Data of GJ 436b were obtained from the HST proposals 12034, PI: J. Green (University of Colorado, Boulder), et al. and 12956: PI: D. Ehrenreich (Observatory of the University of Geneva, Switzerland), et al. The science team comprises: D. Ehrenreich and V. Bourrier (Observatory of the University of Geneva, Switzerland), P. Wheatley (University of Warwick, UK), A. Lecavelier des Etangs (CNRS, Institut d'Astrophysique de Paris), G. Hebrard (Institut d'Astrophysique de Paris/Observatoire de Haute-Provence), S. Udry (Observatory of the University of Geneva, Switzerland), X. Bonfils and X. Delfosse (University of Grenoble, France), J.-M. Desert (CASA), D. Sing (University of Exeter), and A. Vidal-Madjar (Institut d'Astrophysique de Paris). - InstrumentInstrumentThe science instrument used to produce the data.HST>STIS
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.December 7, 2012, June 18, 2013, and June 23, 2014
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.GJ 436b
- Object DescriptionObject DescriptionThe type of astronomical object.Exoplanet
- Release DateJune 24, 2015
- Science ReleaseHubble Sees a ‘Behemoth’ Bleeding Atmosphere Around a Warm Neptune-Sized Exoplanet
- Credits
Related Images & Videos

Polar View of GJ 436b System
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Photometry of Transiting Planet GJ 436b
This artist's diagram shows the unusual light curve produced when the exoplanet GJ 436b and the huge, comet-like hydrogen cloud nicknamed "The Behemoth" pass in front of the parent star. Because the planet's orbit is tilted nearly edge-on to our view from Earth, the planet and...
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Last Updated
Feb 17, 2025
Contact
Media
Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov