Kepler-20

Coordinates: Sky map 19h 10m 47.5s, +42° 20′ 19.4″
Source: Wikipedia, the free encyclopedia.
Kepler-20
Observation data
Epoch J2000      Equinox J2000
Constellation Lyra
Right ascension 19h 10m 47.52334s[1]
Declination +42° 20′ 19.3014″[1]
Apparent magnitude (V) 12.51[2]
Characteristics
Spectral type G8V[3]
Distance
934 ± 3 ly
(286.2 ± 0.8 pc)
Details
Gyr
Other designations
KOI-070, KIC 6850504, 2MASS J19104752+4220194, Gaia DR2 2102548708017562112.[3]
Database references
SIMBADdata
KICdata

Kepler-20 is a star about 934

stellar class G8 star.[7][8] The abundance of elements other than hydrogen or helium, what astronomers term the metallicity, is approximately the same as in the Sun. It may be older than the Sun, although the margin of error here is relatively large.[9]

Planetary system

Size comparison of Kepler-20e and Kepler-20f (artist's impressions) with Venus and Earth (actual photographs)

On December 20, 2011, the

extrasolar planets, Kepler-20e (the first known extrasolar planet smaller than Earth orbiting a main-sequence star)[10] and Kepler-20f, orbiting a Sun-like star.[11] Although the planets are Earth-sized, they are not Earth-like in the respect that they are much closer to their star than Earth, and are hence not near the habitable zone,[12] with expected surface temperatures of 760 °C (1,400 °F) and 427 °C (801 °F), respectively. The three other Neptune-sized planets in the system, Kepler-20b, Kepler-20c, and Kepler-20d, all orbit similarly close to the star.[13][14]

Only upper limits on the masses of e and f are known. Their masses are uncertain as they are too small to detect via radial velocity with current technology.[8] As of 2023, Kepler-20e is known to be less massive than Earth.[4]

A 2016 study detected a sixth planet in the system based on radial velocity observations. Kepler-20g may be a non-transiting Neptunian world.[15] However, the existence of this planet was challenged in 2019,[16] and a non-detection was reported in 2023.[4] Another 2023 study listed this planet, though the data used was identical to the 2016 study except for the addition of a single data point, and the dispute was not addressed.[17]: 24 

All planets are at small near resonances; proceeding outwards, they are 3:2, 4:2, 2:1, 4:1. The planetary orbits in current form are highly sensitive to perturbations caused by outer planets, therefore assuming stability, no additional gas giant planets can be located closer than 30 AU from the parent star.[18]

The Kepler-20 planetary system[4][15]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b 9.7±1.3 M🜨 0.04565±0.00089 3.6961049(16) <0.083 87.36+0.22
−1.6° 		1.773+0.053
−0.030 R🜨
e <0.76 M🜨 0.0637±0.0012 6.0984882(99) <0.092 87.63+1.1
−0.13° 		0.821±0.022 R🜨
c 11.1±2.1 M🜨 0.0936±0.0018 10.8540774(21) <0.076 89.815+0.036
−0.63° 		2.894+0.036
−0.033 R🜨
f <1.4 M🜨 0.1387±0.0027 19.578328(48) <0.094 88.788+0.43
−0.072° 		0.952+0.047
−0.087 R🜨
g (disputed) ≥19.96+3.08
−3.61 M🜨 		0.2055+0.0022
−0.0021 		34.940+0.038
−0.035 		≤0.16 — —
d 13.4+3.7
−3.6 M🜨 		0.3474±0.0067 77.611455(96) <0.082 89.708+0.17
−0.053° 		2.606+0.053
−0.039 R🜨

See also

References

  1. ^
    S2CID 244398875
    . Gaia DR3 record for this source at VizieR.
  2. S2CID 17641056
  3. ^
    Centre de Données astronomiques de Strasbourg
  4. ^
    S2CID 258078829
    .
  5. ^ Johnson, Michele (20 December 2011). "NASA Discovers First Earth-size Planets Beyond Our Solar System". NASA. Retrieved 20 December 2011.
  6. ISBN 0-486-42820-6
  7. Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original
    on 18 March 2012, retrieved 16 January 2012
  8. ^
    S2CID 3182266
    .
  9. ^ Schneider, Jean, "Star : Kepler-20", Extrasolar Planets Encyclopaedia, archived from the original on 2012-01-19, retrieved 2011-12-21
  10. ^ NASA Staff. "Artist's Concept of Kepler-20e". NASA. Retrieved 19 November 2014.
  11. ^ NASA.gov
  12. S2CID 122575277
    .
  13. New York Times
    . Retrieved 2011-12-21.
  14. ^ Tate, Karl (20 December 2011). "At Last, Earth-Sized Alien Worlds (Infographic)". Space.com. Retrieved 2011-12-21.
  15. ^
    S2CID 216077870
    .
  16. S2CID 207853397
  17. doi:10.3847/1538-4365/ad0cab
    .
  18. S2CID 119325005

External links

Wikimedia Commons has media related to Kepler-20.


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