GJ 1214 b

Coordinates: Sky map 17h 15m 18.94s, +4° 57′ 49.7″
Source: Wikipedia, the free encyclopedia.
GJ 1214 b / Enaiposha
Transit (MEarth Project)
Designations
Enaiposha[2]
Orbital characteristics[3]
0.01490±0.00026 AU
Eccentricity<0.063
1.580404571(42) d[4]
Inclination88.7°±0.1°
Semi-amplitude14.36±0.53 m/s
StarOrkaria
Physical characteristics
Mean radius
2.742+0.050
−0.053 R🜨[3]
Mass8.17±0.43 M🜨[3]
Mean density
2.20+0.17
−0.16 g/cm3[3]
10.65+0.71
−0.67 m/s2[3] (1.09 g)
19.31+0.53
−0.54 km/s[3]
Albedo0.51±0.06 (Bond)[5]
Temperature553±9 K (280 °C; 536 °F, dayside)[5]
437±19 K (164 °C; 327 °F, nightside)[5]

GJ 1214 b (sometimes Gliese 1214 b,

ocean planet.[1][7] For that reason, scientists often call the planet a "waterworld".[8]

It is a super-Earth, meaning it is larger than Earth but is significantly smaller (in mass and radius) than the gas giants of the Solar System. After CoRoT-7b, it was the second super-Earth to have both its mass and radius measured[1] and is the first of a new class of planets with small size and relatively low density.[9] 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.[1]

In December 2013, NASA reported that

clouds may have been detected in the atmosphere of GJ 1214 b.[10][11][12][13]

Name

In August 2022, this planet and its host star were included among 20 systems to be named by the third NameExoWorlds project.[14] The approved names, proposed by a team from Kenya, were announced in June 2023. GJ 1214 b is named Enaiposha and its host star is named Orkaria, after the Maa words for a large body of water and for red ochre, alluding to the likely composition of the planet and color of the star.[2]

Physical characteristics

Mass, radius and temperature

Artist's impression of the planet with a hazy steam atmosphere[15]
Artist's impression of GJ 1214 b (foreground), illuminated by the red light of its parent star (center)
The newly discovered super-Earth orbiting the nearby star GJ 1214.
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.

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, yielding a radius of 2.742+0.050
−0.053 R🜨.[3] 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,[1] yielding a mass of 8.17±0.43 M🜨.[3] 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.[1]

GJ 1214 b may be cooler than any other known

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.[1][16]

Atmosphere

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.[17] Because of the estimated old age of the planetary system and the calculated hydrodynamic escape (loss of gasses that tends to deplete an atmosphere of higher molecular-weight constituents) rate of 900 tonnes per second, scientists conclude that there has been a significant atmospheric loss during the lifetime of the planet and any current atmosphere cannot be primordial.[1] The loss of primordial atmosphere was indirectly confirmed in 2020 as no helium was detected at GJ 1214 b.[18] Helium was detected in the atmosphere of GJ 1214 b by 2022 though.[19]

Possible compositions

While very little is known about GJ 1214 b, there has been speculation as to its specific nature and composition. On the basis of planetary models

pressure at depth, models of a water world include "steam, liquid, superfluid, high-pressure ices, and plasma phases" of water.[9] Some of the solid-phase water could be in the form of ice VII.[16]

Discovery

GJ 1214 b was first detected by the MEarth Project, which searches for the small drops in brightness that can occur when an orbiting planet briefly passes in front of its parent star. In early 2009, the astronomers running the project noticed that the star GJ 1214 appeared to show drops in brightness of that sort. They then observed the star more closely and confirmed that it dimmed by roughly 1.5% every 1.58 days. Follow-up radial-velocity measurements were then made with the HARPS spectrograph on the ESO's 3.6-meter telescope at La Silla, Chile; those measurements succeeded in providing independent evidence for the reality of the planet. A paper was then published in Nature announcing the planet and giving estimates of its mass, radius, and orbital parameters.[1]

See also

References

  1. ^
    S2CID 4360404
    .
  2. ^ a b c "2022 Approved Names". nameexoworlds.iau.org. IAU. Retrieved 7 June 2023.
  3. ^
    S2CID 236635146
    .
  4. doi:10.3847/1538-4365/ac9da4. Vizier catalog entry
  5. ^
    doi:10.1038/s41586-023-06159-5
    .
  6. ^ Rein, Hanno; et al. "Open Exoplanet Catalogue – Gliese 1214 b". Open Exoplanet Catalogue. Retrieved 2 January 2014.
  7. S2CID 8369390
    .
  8. ^ "10 real planets that are stranger than science fiction". iflscience.com. Retrieved 2015-06-13.
  9. ^ a b c d e f g Rogers, L.A.; Seager, S. (2010). "Three possible origins for the gas layer on GJ 1214 b".
    S2CID 15288792
    .
  10. ^ Harrington, J.D.; Weaver, Donna; Villard, Ray (December 31, 2013). "Release 13-383 – NASA's Hubble Sees Cloudy Super-Worlds With Chance for More Clouds". NASA. Retrieved January 1, 2014.
  11. S2CID 4408861
    .
  12. S2CID 4454617
    .
  13. S2CID 4447642
    .
  14. ^ "List of ExoWorlds 2022". nameexoworlds.iau.org. IAU. 8 August 2022. Retrieved 27 August 2022.
  15. ^ Brennan, Pat (10 May 2023). "NASA's Webb Takes Closest Look Yet at Mysterious Planet". NASA. Retrieved 10 May 2023.
  16. ^ a b c Aguilar, David A. (2009-12-16). "Astronomers find super-Earth using amateur, off-the-shelf technology".
    Harvard-Smithsonian Center for Astrophysics
    . Retrieved December 16, 2009.
  17. S2CID 4412196
    .
  18. S2CID 220793801
    .
  19. S2CID 246285597
    .
  20. ^ a b Seager, S.; Kuchner, M.; Hier-Majumder, C.A.; Militzer, B. (2007). "Mass–radius relationships for solid exoplanets". The Astrophysical Journal. 669 (2): 1279–1297.
    S2CID 8369390
    .

External links

Media related to GJ 1214 b at Wikimedia Commons

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