Kepler-20

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Kepler-20
Observation data
Epoch J2000      Equinox J2000
Constellation Lyra
Right ascension 19h 10m 47.524s[1]
Declination +42° 20′ 19.30″[1]
Apparent magnitude (V) 12.51[2]
Characteristics
Spectral type G8[3]
Astrometry
Proper motion (μ) RA: –4.2[1] mas/yr
Dec.: –26.3[1] mas/yr
Distance ca. 950 ly
(290 ± 30[4] pc)
Details
Mass 0.912±0.035[4] M☉
Radius 0.944+0.06
−0.095[4] R☉
Temperature 5466±93[4] K
Metallicity [Fe/H] 0.02±0.04[4] dex
Age 8.8+4.7
−2.7[4] Gyr
Other designations
KOI-070, KIC-6850504, 2MASS J19104752+4220194.[3]

Kepler-20 is a star 950 light-years from Earth[5] in the constellation Lyra with a system of five known planets.[6] The apparent magnitude of this star is 12.51, so it cannot be seen with the unaided eye. Viewing it requires a telescope with an aperture of Lua error in Module:Convert at line 1851: attempt to index local 'en_value' (a nil value). or more.[7] It is slightly smaller than the Sun, with 94% of the Sun's radius and about 91% of the Sun's mass. The effective temperature of the photosphere is slightly cooler than that of the Sun at 5466 K, giving it the characteristic yellow hue of a stellar class G8 star.[8][9] 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.[4]

Planetary system

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

On December 20, 2011, the Kepler Space Telescope team reported the discovery of a five planet system containing three small gas giants and the first two Earth-sized 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,[5] 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.[12][13]

The masses of e and f are expected masses. Their masses are uncertain as they are too small to detect via radial velocity with current technology.[14]

All planets are at small near resonances; proceeding outwards, they are 3:2, 4:2, 2:1, 4:1.

The Kepler-20 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 8.7 M⊕ 0.04537 3.6961219 <0.32 — 1.91 R⊕
e 0.39–1.67 M⊕ 0.0630 6.098493 <0.28 — 0.868 R⊕
c 16.1 M⊕ 0.0930 10.854092 <0.40 — 3.07 R⊕
f 0.66–3.04 M⊕ 0.1370 19.57706 <0.32 — 1.034 R⊕
d <20.1 M⊕ 0.3453 77.61184 <0.60 — 2.75 R⊕

See also

References

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External links

Coordinates: Sky map 19h 10m 47.5s, +42° 20′ 19.4″

  1. ↑ 1.0 1.1 1.2 1.3 Lua error in package.lua at line 80: module 'strict' not found. See the online data VizieR results for 3UC 265-159969.
  2. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ http://kepler.nasa.gov/news/nasakeplernews/index.cfm?FuseAction=ShowNews&NewsID=172
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ http://arxiv.org/abs/1112.4550
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