Gliese 436 b

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Gliese 436 b
Exoplanet List of exoplanets
Exoplanet Comparison Gliese 436 b.png
Size comparison of Gliese 436 b with Neptune
Parent star
Star Gliese 436
Constellation Leo[1]
Right ascension (α) 11h 42m 11.0932s[2]
Declination (δ) +26° 42′ 23.653″[2]
Apparent magnitude (mV) 10.68
Distance31.80±0.10[2] ly
(9.75±0.03[2] pc)
Spectral type M2.5 V[3]
Mass (m) 0.41 ± 0.05 M
Radius (r) 0.42 R
Temperature (T) 3318 K
Metallicity [Fe/H] -0.32
Age 7.41–11.05[4] Gyr
Orbital elements
Semi-major axis(a) 0.028±0.01[5] AU
Eccentricity (e) 0.152+0.009
Orbital period(P) 2.643904±0.000005[6] d
Inclination (i) 85.8+0.21
Argument of
(ω) 325.8+5.5
Time of periastron (T0) 2451552.077[5] JD
Semi-amplitude (K) 17.38±0.17[5] m/s
Physical characteristics
[5] M
Radius(r)4.327±0.183[7][8] R
Stellar flux(F)29.5
Density(ρ)1.51 g cm−3
Surface gravity(g)1.18 g
Temperature (T) 712±36[7]
Discovery information
Discovery date August 31, 2004
Discoverer(s) Butler, Vogt,
Marcy et al.
Discovery method Radial velocity, Transit
Discovery site California, USA
Discovery status Published
Other designations
Ross 905 b, GJ 436 b,[9]
Database references
Extrasolar Planets
Exoplanet Archivedata
Open Exoplanet Cataloguedata

Gliese 436 b /ˈɡlzə/ (sometimes called GJ 436 b[10]) is a Neptune-sized exoplanet orbiting the red dwarf Gliese 436.[11] It was the first hot Neptune discovered with certainty (in 2007) and was among the smallest-known transiting planets in mass and radius, until the much smaller Kepler exoplanet discoveries started coming in by 2010.

In December 2013, NASA reported that clouds may have been detected in the atmosphere of GJ 436 b.[12][13][14][15]


Gliese 436 b was discovered in August 2004 by R. Paul Butler and Geoffrey Marcy of the Carnegie Institute of Washington and University of California, Berkeley, respectively, using the radial velocity method. Together with 55 Cancri e, it was then the first of a new class of planets with a minimum mass (M sini) similar to Neptune.

The planet was recorded to transit its star by an automatic process at NMSU on January 11, 2005, but this event went unheeded at the time.[16] In 2007, Gillon led a team which observed the transit, grazing the stellar disc relative to Earth. Transit observations led to the determination of Gliese 436 b's exact mass and radius, both of which are very similar to Neptune. Gliese 436 b then became the smallest-known transiting extrasolar planet. The planet is about 4,000 km larger in diameter than Uranus and 5,000 km larger than Neptune and a bit more massive. Gliese 436b (also known as GJ 436b) orbits its star at a distance of 4,000,000 km or 15 times closer than Mercury's average distance from the Sun.

Physical characteristics[edit]

Possible interior structure of Gliese 436 b
Formation of a helium atmosphere on a helium planet, possibly like Gliese 436 b.

The planet's surface temperature is estimated from measurements taken as it passes behind the star to be 712 K (439 °C; 822 °F).[7] This temperature is significantly higher than would be expected if the planet were only heated by radiation from its star, which was prior to this measurement, estimated at 520 K. Whatever energy tidal effects deliver to the planet, it does not affect its temperature significantly.[17] A greenhouse effect could raise the temperature to much higher degrees than the predicted 520–620 K.[18]

Its main constituent was initially predicted to be hot "ice" in various exotic high-pressure forms,[18][19] which would remain solid despite the high temperatures, because of the planet's gravity.[20] The planet could have formed further from its current position, as a gas giant, and migrated inwards with the other gas giants. As it arrived in range, the star would have blown off the planet's hydrogen layer via coronal mass ejection.[21]

However, when the radius became better known, ice alone was not enough to account for it. An outer layer of hydrogen and helium up to ten percent in mass would be needed on top of the ice to account for the observed planetary radius.[7][6] This obviates the need for an ice core. Alternatively, the planet may be a super-earth.[22]

Observations of the planet's brightness temperature with the Spitzer Space Telescope suggest a possible thermochemical disequilibrium in the atmosphere of this exoplanet. Results published in Nature suggest that Gliese 436b's dayside atmosphere is abundant in CO and deficient in methane (CH4) by a factor of ~7,000. This result is unexpected because, based on current models at this temperature, the atmospheric carbon should prefer CH4 over CO.[23][24][25][26]

In June 2015, scientists reported that the atmosphere of Gliese 436 b was evaporating,[27] resulting in a giant cloud around the planet and, due to radiation from the host star, a long trailing tail 14×10^6 km (9×10^6 mi) long.[28]

Artist impression of Gliese 436b shows the enormous comet-like cloud of hydrogen boiling off.[29]

Orbital characteristics[edit]

One orbit around the star takes only about 2 days, 15.5 hours. Gliese 436 b's orbit is likely misaligned with its star's rotation.[25]

The eccentricity of Gliese 436 b's orbit is inconsistent with models of planetary system evolution. To have maintained its eccentricity over time requires that it be accompanied by another planet.[7][30]

A study published in Nature in December 2017 found that the orbit of Gliese 436 b is nearly perpendicular to the stellar equator of Gliese 436, and suggests that the eccentricity and misalignment of the orbit could have resulted from interactions with a yet-undetected companion. The inward migration caused by this interaction could have triggered the atmospheric escape that sustains its giant exosphere.[31]

See also[edit]


  1. Roman, Nancy G. (1987). "Identification of a Constellation From a Position". Publications of the Astronomical Society of the Pacific 99 (617): 695–699. Bibcode 1987PASP...99..695R. doi:10.1086/132034. Vizier query form
  2. 2.0 2.1 2.2 2.3 Brown, A. G. A. et al. (2016). "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties". Astronomy and Astrophysics 595: A2. arXiv:1609.04172. Bibcode 2016A&A...595A...2G. doi:10.1051/0004-6361/201629512. Data Release 1 catalog entry
  3. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  4. Saffe, C.; Gómez, M.; Chavero, C. (2006). "On the Ages of Exoplanet Host Stars". Astronomy & Astrophysics 443 (2): 609–626. arXiv:astro-ph/0510092. Bibcode 2005A&A...443..609S. doi:10.1051/0004-6361:20053452.
  5. 5.0 5.1 5.2 5.3 5.4 5.5 Trifonov, T. et al. (2018). "The CARMENES search for exoplanets around M dwarfs. First visual-channel radial-velocity measurements and orbital parameter updates of seven M-dwarf planetary systems". Astronomy and Astrophysics 609: A117. arXiv:1710.01595. Bibcode 2018A&A...609A.117T. doi:10.1051/0004-6361/201731442.
  6. 6.0 6.1 6.2 Bean, J.L. (2008). "A Hubble Space Telescope transit light curve for GJ 436b". Astronomy & Astrophysics 486: 1039–1046. arXiv:0806.0851. Bibcode 2008A&A...486.1039B. doi:10.1051/0004-6361:200810013.
  7. 7.0 7.1 7.2 7.3 7.4 Drake Deming; Joseph Harrington; Gregory Laughlin; Sara Seager; Navarro, Sarah B.; Bowman, William C.; Karen Horning (2007). "Spitzer Transit and Secondary Eclipse Photometry of GJ 436b". The Astrophysical Journal 667 (2): L199–L202. arXiv:0707.2778. Bibcode 2007ApJ...667L.199D. doi:10.1086/522496.
  8. Confirmed, Pont, F.; Gilliland, R. L.; Knutson, H.; Holman, M.; Charbonneau, D. (2008). "Transit infrared spectroscopy of the hot neptune around GJ 436 with the Hubble Space Telescope". Monthly Notices of the Royal Astronomical Society: Letters 393: L6–L10. arXiv:0810.5731. Bibcode 2009MNRAS.393L...6P. doi:10.1111/j.1745-3933.2008.00582.x.
  9. Maness; Marcy, G. W.; Ford, E. B.; Hauschildt, P. H.; Shreve, A. T.; Basri, G. B.; Butler, R. P.; Vogt, S. S. (2006). "The M Dwarf GJ 436 and its Neptune-Mass Planet". Submitted to Publications of the Astronomical Society of the Pacific 119 (851): 90–101. arXiv:astro-ph/0608260. Bibcode 2007PASP..119...90M. doi:10.1086/510689.
  10. Beust,Hervé (August 1, 2012). "Dynamical evolution of the Gliese 436 planetary system - Kozai migration as a potential source for Gliese 436b's eccentricity". Astronomy 545: A88. arXiv:1208.0237. Bibcode 2012A&A...545A..88B. doi:10.1051/0004-6361/201219183.
  11. Butler, R. Paul et al. (2004). "A Neptune-Mass Planet Orbiting the Nearby M Dwarf GJ 436". The Astrophysical Journal 617 (1): 580–588. arXiv:astro-ph/0408587. Bibcode 2004ApJ...617..580B. doi:10.1086/425173.
  12. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  13. Moses, Julianne (January 1, 2014). "Extrasolar planets: Cloudy with a chance of dustballs". Nature 505 (7481): 31–32. Bibcode 2014Natur.505...31M. doi:10.1038/505031a. PMID 24380949. Retrieved January 1, 2014.
  14. Knutson, Heather (January 1, 2014). "A featureless transmission spectrum for the Neptune-mass exoplanet GJ 436b". Nature 505 (7481): 66–68. arXiv:1401.3350. Bibcode 2014Natur.505...66K. doi:10.1038/nature12887. PMID 24380953. Retrieved January 1, 2014.
  15. Kreidberg, Laura (January 1, 2014). "Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b". Nature 505 (7481): 69–72. arXiv:1401.0022. Bibcode 2014Natur.505...69K. doi:10.1038/nature12888. PMID 24380954. Retrieved January 1, 2014.
  16. Coughlin, Jeffrey L.; Stringfellow, Guy S.; Becker, Andrew C.; Mercedes Lopez-Morales; Fabio Mezzalira; Tom Krajci (2008). "New observations and a possible detection of parameter variations in the transits of Gliese 436b". The Astrophysical Journal 689 (2): L149–L152. arXiv:0809.1664. Bibcode 2008ApJ...689L.149C. doi:10.1086/595822.
  17. Brian Jackson; Richard Greenberg; Rory Barnes (2008). "Tidal Heating of Extra-Solar Planets". The Astrophysical Journal 681 (2): 1631–1638. arXiv:0803.0026. Bibcode 2008ApJ...681.1631J. doi:10.1086/587641.
  18. 18.0 18.1 M. Gillon (2007). "Detection of transits of the nearby hot Neptune GJ 436 b" (PDF). Astronomy and Astrophysics 472 (2): L13–L16. arXiv:0705.2219. Bibcode 2007A&A...472L..13G. doi:10.1051/0004-6361:20077799.
  19. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  20. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  21. H. Lammer (2007). "The impact of nonthermal loss processes on planet masses from Neptunes to Jupiters". Geophysical Research Abstracts 9 (07850). By analogy with Gliese 876 d.
  22. E. R. Adams; S. Seager; L. Elkins-Tanton (February 2008). "Ocean Planet or Thick Atmosphere: On the Mass-Radius Relationship for Solid Exoplanets with Massive Atmospheres". The Astrophysical Journal 673 (2): 1160–1164. arXiv:0710.4941. Bibcode 2008ApJ...673.1160A. doi:10.1086/524925.
  23. Stevenson, KB; Harrington, J; Nymeyer, S et al. (22 April 2010). "Possible thermochemical disequilibrium in the atmosphere of the exoplanet GJ 436b". Nature 464 (7292): 1161–1164. arXiv:1010.4591. Bibcode 2010Natur.464.1161S. doi:10.1038/nature09013. PMID 20414304.
  24. GJ436b - Where's the methane? Archived 2010-05-14 at the Wayback Machine. Planetary Sciences Group at the University of Central Florida, Orlando
  25. 25.0 25.1 Knutson, Heather A. (2011). "A Spitzer Transmission Spectrum for the Exoplanet GJ 436b". Astrophysical Journal 735, 27: 27. arXiv:1104.2901. Bibcode 2011ApJ...735...27K. doi:10.1088/0004-637X/735/1/27.
  26. LINE, Michael R.; VASISHT, Gautam; CHEN, Pin; ANGERHAUSEN, D.; YANG, Yuk L. (2011). "Thermochemical and Photochemical Kinetics in Cooler Hydrogen Dominated Extrasolar Planets". Astrophysical Journal 738, 32: 32. arXiv:1104.3183. Bibcode 2011ApJ...738...32L. doi:10.1088/0004-637X/738/1/32., abstract in the arXiv titled "Thermochemistry and Photochemistry in Cooler Hydrogen Dominated Extrasolar Planets: The Case of GJ436b"
  27. D. Ehrenreich; V. Bourrier; P. Wheatley; A. Lecavelier des Etangs; G. Hébrard; S. Udry; X. Bonfils; X. Delfosse et al. (25 June 2015). "A Giant Comet-like Cloud of Hydrogen Escaping from the warm Neptune-mass Exoplanet GJ 436b". Nature 522: 459–461. arXiv:1506.07541. Bibcode 2015Natur.522..459E. doi:10.1038/nature14501. PMID 26108854.
  28. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  29. Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).
  30. Lua error in Module:Citation/CS1 at line 876: attempt to call method 'sub' (a nil value).
  31. Bourrier, Vincent et al. (2018). "Orbital misalignment of the Neptune-mass exoplanet GJ 436b with the spin of its cool star". Nature 553 (7689): 477–480. arXiv:1712.06638. Bibcode 2018Natur.553..477B. doi:10.1038/nature24677.

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