page_title: Gliese 1214 b
section_title: Features
hierarchical_section_title: Gliese 1214 b / Features
caption_attribution_description: This artist’s impression shows the super-Earth exoplanet GJ 1214b passing in front of its faint red parent star. This is the first super-Earth exoplanet to have had its atmosphere analysed. The exoplanet, orbiting a small star only 40 light-years away from us, has a mass about six times that of the Earth. GJ 1214b appears to be surrounded by an atmosphere that is either dominated by steam or blanketed by thick clouds or hazes.
context_page_description: Gliese 1214 b is an exoplanet that orbits the star Gliese 1214, and was discovered in December 2009. Its parent star is 48 light-years from the Sun, in the constellation Ophiuchus. As of 2017, GJ 1214 b is the most likely known candidate for being an ocean planet. For that reason, scientists have nicknamed the planet "the waterworld".
  It is a super-Earth, meaning it is larger than Earth but is significantly smaller than the gas giants of the Solar System. After COROT-7b, it was the second super-Earth to be known and is the first of a new class of planets with small size and relatively low density. GJ 1214 b is also significant because its parent star is relatively near the Sun and because it transits that parent star, which allows the planet's atmosphere to be studied using spectroscopic methods.
  In December 2013, NASA reported that clouds may have been detected in the atmosphere of GJ 1214 b.
context_section_description: The radius of GJ 1214 b can be inferred from the amount of dimming seen when the planet crosses in front of its parent star as viewed from Earth.  The mass of the planet can be inferred from sensitive observations of the parent star's radial velocity, measured through small shifts in stellar spectral lines due to the Doppler effect. Given the planet's mass and radius, its density can be calculated. Through a comparison with theoretical models, the density in turn provides limited but highly useful information about the composition and structure of the planet.
  
  Due to the relatively small size of GJ 1214 b's parent star, it is feasible to perform spectroscopic observations during planetary transits.  By comparing the observed spectrum before and during transits, the spectrum of the planetary atmosphere can be inferred. In December 2010, a study was published showing the spectrum to be largely featureless over the wavelength range of 750–1000 nm. Because a thick and cloud-free hydrogen-rich atmosphere would have produced detectable spectral features, such an atmosphere appears to be ruled out. Although no clear signs were observed of water vapor or any other molecule, the authors of the study believe the planet may have an atmosphere composed mainly of water vapor. Another possibility is that there may be a thick layer of high clouds, which absorbs the starlight. Further observations are necessary to determine the composition of its atmosphere.
  Because of the estimated old age of the planetary system and the calculated hydrodynamic escape rate of 9×10⁵ kg s⁻¹, scientists conclude that there has been a significant atmospheric loss during the lifetime of the planet and any current atmosphere cannot be primordial. The loss of primordial atmosphere was indirectly confirmed in 2020 as no helium was detected at Gliese 1214 b.
  GJ 1214 b may be cooler than any other known transiting planet prior to the discovery of Kepler-16b in 2011 by the Kepler mission. Its equilibrium temperature is believed to be in the range of 393–555 K (120–282 °C; 248–539 °F), depending on how much of the star's radiation is reflected into space.
caption: This artist's impression shows how GJ 1214 b may look as it transits its parent star. It is the second super-Earth for which astronomers have determined the mass and radius, giving vital clues about its structure.
exif: {"Image ImageDescription": "This artist\u2019s impression shows the super-Earth exoplanet GJ 1214b passing in front of its faint red parent star. This is the first super-Earth exoplanet to have had its atmosphere analysed. The exoplanet, orbiting a small star only 40 light-years away from us, has a mass about six times that of the Earth. GJ 1214b appears to be surrounded by an atmosphere that is either dominated by steam or blanketed by thick clouds or hazes."}