Kepler-20

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Star
Kepler-20
Search map for Kepler-20 in the constellation Lyra
Search map for Kepler-20 in the constellation Lyra
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation lyre
Right ascension 19 h 10 m 47.52 s
declination + 42 ° 20 ′ 19.3 ″
Apparent brightness 12.51 mag
Typing
Known exoplanets 5
Spectral class G8
Astrometry
distance approx. 950  ly
290 ± 30  pc  
Proper movement 
Rec. Share: -4.2  mas / a
Dec. portion: -26.3  mas / a
Physical Properties
Dimensions 0.912 ± 0.035  M ☉
radius 0.944 +0.06−0.095 R ☉
Effective temperature 5,466 ± 93  K
Metallicity [Fe / H] 0.02 ± 0.04
Age 8.8 +4.7−2.7Billion  a
Other names
and catalog entries
2MASS catalog 2MASS J19104752 + 4220194 [1]
Other names Kepler-20, KOI-070, KIC-6850504

Kepler-20 is a star in the constellation Lyra, 950 light years from Earth , with a planetary system made up of five known exoplanets . With an apparent magnitude of 12.51 mag, it cannot be seen with the naked eye. Observation requires a telescope with an aperture of at least 15 cm (6 inches) or more.

Kepler-20 is slightly smaller than the sun , has 94% of the solar radius and about 91% of the solar mass . The effective temperature of the star's photosphere is 5,466 Kelvin and is slightly cooler than that of the Sun, which gives it the characteristic yellow glow of a yellow dwarf star belonging to spectral class G8. The abundance of elements other than hydrogen or helium, known by astronomers as metallicity , is estimated to be the same as that of the sun. Kepler-20 is probably older than the Sun, but here the error range is relatively large.

Planetary system

Size comparison of the planets Kepler-20e and Kepler-20f (artistic impression) with Venus and Earth (current photographs)

On December 20, 2011, the team of scientists at the Kepler Space Telescope announced the discovery of a system of five planets, consisting of three gas planets and the two roughly Earth-sized planets Kepler-20e and Kepler-20f. Kepler-20e is the first known exoplanet around a main sequence star that is smaller than Earth.

Although the two planets are roughly the size of Earth, they are in no way to be called Earth-like, as they orbit their star at a much smaller distance than the Earth orbits the Sun and they are therefore far outside the habitable zone , with temperatures on theirs Surface is estimated to reach 760 ° C and 427 ° C, respectively. The three other planets Kepler-20b, Kepler-20c, and Kepler-20d are roughly the size of Neptune and also orbit the central star in very close orbits.

The masses of Kepler-20e and Kepler-20f are estimated. Their mass determination is uncertain because they are too small to be detected with current technology using the radial velocity method .

All planets are in orbital resonances . From the inside out, these are 3: 2, 4: 2, 2: 1 and 4: 1.

Planetary system from Kepler-20

Planet
(by distance from the star) 		Discovery
(year) 		Radius
(in ) 		Mass
(in M ⊕ ) 		Cycle time
(in days) 		Major semi-axis
(in AU ) 		Orbit inclination
(in ) 		eccentricity
Kepler-20b 2011 1.91 8.7 3,6961219 0.04537 - <0.32
Kepler-20e 2011 0.868 0.39-1.67 6,098493 0.0630 - <0.28
Kepler-20c 2011 3.07 16.1 10.854092 0.0930 - <0.40
Kepler-20f 2011 1.034 0.66-3.04 19.57706 0.1370 - <0.32
Kepler-20d 2011 2.75 <20.1 77.61184 0.3453 - <0.60

See also

Individual evidence

  1. ↑ a b c d e f g Zacharias, N. et al .: The Third US Naval Observatory CCD Astrograph Catalog (UCAC3) . arxiv : 1003.2136 .
  2. ↑ Lasker, Barry M. et al .: The Second-Generation Guide Star Catalog: Description and Properties . arxiv : 0807.2522 .
  3. ↑ a b c SIMBAD: Kepler-20 - Star. Retrieved April 9, 2015 .
  4. ↑ a b The Extrasolar Planets Encyclopaedia: Planet Kepler-20 b. Retrieved April 9, 2015 .
  5. ↑ a b Eric Hand: Kepler discovers first Earth-sized exoplanets. Retrieved April 9, 2015 .
  6. ^ National Aeronautics and Space Administration: NASA Discovers First Earth-size Planets Beyond Our Solar System. Retrieved April 9, 2015 .
  7. ↑ Sherrod, P. Clay; Koed, Thomas L .: A Complete Manual of Amateur Astronomy: Tools and Techniques for Astronomical Observations. Retrieved April 9, 2015 .
  8. ^ Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organization): The Color of Stars. Retrieved April 9, 2015 .
  9. ↑ Fressin, Francois; Torres, Guillermo; Rowe, Jason F .; Charbonneau, David; Rogers, Leslie A .; Ballard, Sarah; Batalha, Natalie M .; Borucki, William J .; Bryson, Stephen T .; Buchhave, Lars A .; Ciardi, David R .; Désert, Jean-Michel; Dressing, Courtney D .; Fabrycky, Daniel C .; Ford, Eric B .; Gautier III, Thomas N .; Henze, Christopher E .; Holman, Matthew J .; Howard, Andrew; Howell, Steve B .; Jenkins, Jon M .; Koch, David G .; Latham, David W .; Lissauer, Jack J .; Marcy, Geoffrey W .; Quinn, Samuel N .; Ragozzine, Darin; Sasselov, Dimitar D .; Seager, Sara; Barclay, Thomas; Mullally, Fergal; Seader, Shawn E .; Still, Martin; Twicken, Joseph D .; Thompson, Susan E .; Uddin, Kamal: Two Earth-sized planets orbiting Kepler-20 . arxiv : 1112.4550 .
  10. ^ National Aeronautics and Space Administration: Kepler-20 system: 5 planets including two that are Earth-size. Retrieved April 9, 2015 .
  11. ↑ National Aeronautics and Space Administration: Artist's Concept of Kepler-20e. Retrieved April 9, 2015 .
  12. ↑ New York Times, December 20, 2011: Two Earth-Size Planets Are Discovered. Retrieved April 9, 2015 .
  13. ^ Tate, Karl: At Last, Earth-Sized Alien Worlds (Infographic). Retrieved April 9, 2015 .
  14. ^ Francois Fressin, Guillermo Torres, Jason F. Rowe, David Charbonneau, Leslie A. Rogers, Sarah Ballard, Natalie M. Batalha, William J. Borucki, Stephen T. Bryson, Lars A. Buchhave, David R. Ciardi, Jean- Michel Desert, Courtney D. Dressing, Daniel C. Fabrycky, Eric B. Ford, Thomas N. Gautier III, Christopher E. Henze, Matthew J. Holman, Andrew W. Howard, Steve B. Howell, Jon M. Jenkins, David G. Koch, David W. Latham, Jack J. Lissauer, Geoffrey W. Marcy, Samuel N. Quinn, Darin Ragozzine, Dimitar D. Sasselov, Sara Seager, Thomas Barclay, Fergal Mullally, Shawn E. Seader, Martin Still, Joseph D. Twicken, Susan E. Thompson, Kamal Uddin: Two Earth-sized planets orbiting Kepler-20 . arxiv : 1112.4550 .

Web links

Commons : Kepler-20  - collection of pictures, videos and audio files