Kepler-138

from Wikipedia, the free encyclopedia
Star
Kepler-138
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation lyre
Right ascension 19 h 21 m 31.57 s
declination + 43 ° 17 ′ 34.7 ″
Apparent brightness 13.5 likes
Typing
Known exoplanets 3
Spectral class M0V
Astrometry
distance 217 ± 24  ly
66.5 ± 7.3  pc  
Physical Properties
Dimensions 0.57 ± 0.05  M ☉
radius 0.54 ± 0.05  R ☉
Luminosity

0.060 ± 0.008  L ☉

Effective temperature 3,871 ± 58  K
Metallicity [Fe / H] −0.28 ± 0.10
Rotation time ~ 10 d
Age > 1 billion  a
Other names
and catalog entries
2MASS catalog 2MASS J19213157 + 4317347 [1]
Other names KIC 7603200, KOI-314, Kepler-138

Kepler-138 (also KOI-314 ) is a red dwarf in the constellation Lyra , the approximately 217 light years from the sun away. The star has a planetary system with three known exoplanets .

properties

As a red dwarf, Kepler-138 is significantly smaller and cooler than the sun. It is estimated to be 57% of the solar mass and 54% of the solar radius .

Planetary system

On the basis of the observation data from the Kepler space telescope , an astronomical team was initially able to use the transit method to detect two planets around Kepler-138, the discovery of which was published in early 2014. A third possible planet was initially unconfirmed, but was detected a little later by another research group.

The innermost planet, Kepler-138b , is roughly the size of the planet Mars in the solar system, while the other two, Kepler-138c and Kepler-138d , are each about 1.2 times the radius of Earth . Variations in the transit of the planets ( transit timing ), caused by the interactions of gravitation on neighboring planets, made it possible to estimate their respective masses and thus to draw conclusions about the density. Kepler-138b became the first exoplanet that is smaller than Earth and whose mass could be determined.

According to the model calculations, the mass of Kepler-138b is smaller than that of Mars, its density is relatively low, which is why it possibly contains larger amounts of water. The mass and density of the other two planets differ significantly despite their similar size. According to the model calculations, the middle planet Kepler-138c has a density comparable to that of Earth, while the comparatively low density of Kepler-138d can possibly be explained by a larger proportion of water or hydrogen. It probably has an extensive atmosphere and is therefore more of a small gas planet (→ mini-Neptune ), comparable to Uranus and Neptune in the solar system.

Planetary system by Kepler-138
Planet
(by distance from the star) 		Discovery
(year) 		Mass
(in M ♁ ) 		Radius
(in ) 		Density
(in g / cm 3 ) 		Cycle time
(in days)
Kepler-138b 2014 0.0660 +0.0590−0.0370 0.522 ± 0.032 2.6 +2.4−1.5 10.3126 +0.0004−0.0006
Kepler-138c 2014 1.970 +1.912−1.120 1.197 ± 0.070 6.2 + 5.8−3.4 13.7813 ± 0.0001
Kepler-138d 2014 0.6400 +0.6740−0.3870 1.212 ± 0.075 2.1 +2.2−1.2 23.0881 +0.0009−0.0008

Individual evidence

  1. ↑ SIMBAD: Kepler-138. Retrieved July 25, 2015 .
  2. ^ The Extrasolar Planets Encyclopaedia: Planet Kepler-138. Retrieved July 25, 2015 .
  3. ↑ a b c d e f Pineda, JS; Bottom, M .; Johnson, JA: Planet Kepler-138 . arxiv : 1302.6231 .
  4. ↑ a b Mann, AW; Gaidos, E .; Ansdell, M .: Spectro-Thermometry of M dwarfs and their candidate planets: too hot, too cool, or just right? arxiv : 1311.0003 .
  5. ↑ a b c Kipping, DM; Nesvorny, D .; Buchhave, LA; Hartman, J .; Bakos, GA; Schmitt, AR: The Hunt for exomoons with Kepler (HEK): IV A Search for Moons around Eight M Dwarfs. . arxiv : 1401.1210 .
  6. ^ Rowe, JF et al .: Validation of Kepler's Multiple Planet Candidates. III: Light Curve Analysis & Announcement of Hundreds of New Multi-planet Systems . arxiv : 1402.6534 .
  7. ↑ a b c d Jontof-Hutter, D .; Rowe, JF; Lissauer, JJ; Fabricky, DC; Ford, EB: The mass of the Mars-sized exoplanet Kepler-138 b from transit timing . arxiv : 1506.07067 .
  8. ↑ a b Stars and Space from June 17, 2015: The first mass determination of a Mars-sized exoplanet. Retrieved July 25, 2015 .
  9. ↑ Ron Cowen: Earth-mass exoplanet is no Earth twin. Retrieved July 25, 2015 .
  10. ↑ a b c NASA Exoplanet Archives: Kepler-138. Retrieved July 25, 2015 .