Kepler-186f
| Exoplanet | List of exoplanets | |
|---|---|---|
 |
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| Parent star | ||
| Star | Kepler-186 | |
| Constellation | Cygnus | |
| Right ascension | (α) | 19h 54m 36.651s |
| Declination | (δ) | +43° 57′ 18.06″ |
| Apparent magnitude | (mV) | 14.625 |
| Distance | 558 ly (171 pc) |
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| Spectral type | M1V | |
| Mass | (m) | 0.544 (± 0.02) M☉ |
| Radius | (r) | 0.523 (± 0.02) R☉ |
| Temperature | (T) | 3755 (± 90) K |
| Metallicity | [Fe/H] | −0.26 (± 0.12) |
| Age | 4.0 (± 0.6) Gyr | |
| Physical characteristics | ||
| Mass | (m) | 1.4M⊕ |
| Radius | (r) | 1.17 (± 0.08)R⊕ |
| Stellar flux | (F⊙) | 0.32 +0.06 −0.04⊕ |
| Temperature | (T) | 188 K (−85 °C; −121 °F) |
| Orbital elements | ||
| Semi-major axis | (a) | 0.432 (± 0.01)AU |
| Eccentricity | (e) | 0.04 |
| Orbital period | (P) | 129.9444 (± 0.0012) d (0.355772 y) |
| Inclination | (i) | 89.9° |
| Discovery information | ||
| Discovery date | 17 April 2014 | |
| Discoverer(s) | Elisa Quintana | |
| Discovery method | Transit | |
| Discovery site | Kepler Space Observatory | |
| Discovery status | Published refereed article | |
| Other designations | ||
|
KOI-571.05; Kepler-186 f; K00571.05; 2MASS J19543665+4357180 f; KIC 8120608 f; KOI-571 f; WISE J195436.65+435717.9 f
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| Database references | ||
| Extrasolar Planets Encyclopaedia |
data | |
| SIMBAD | data | |
| Exoplanet Archive | data | |
| Open Exoplanet Catalogue | data | |
Kepler-186f (also known by its Kepler Object of Interest designation KOI-571.05) is an exoplanet orbiting the red dwarf Kepler-186, about 500 light-years (171 parsecs, or nearly 5.298×1015 km) from the Earth. It is the first planet with a radius similar to Earth's to be discovered in the habitable zone of another star. NASA's Kepler spacecraft detected it using the transit method, along with four additional planets orbiting much closer to the star (all modestly larger than Earth). Analysis of three years of data was required to find its signal. The results were presented initially at a conference on 19 March 2014 and some details were reported in the media at the time. The public announcement was on 17 April 2014, followed by publication in Science.
The only physical property directly derivable from the observations (besides the orbital period) is the ratio of the radius of the planet to that of the central star, which follows from the amount of occultation of stellar light during a transit. This ratio was measured to be 0.021. This yields a planetary radius of 1.11±0.14 times that of Earth, taking into account uncertainty in the star's diameter and the degree of occultation. Thus, the planet is about 11% larger in radius than Earth (between 4.5% smaller and 26.5% larger), giving a volume about 1.37 times that of Earth (between 0.87 and 2.03 times as large).
A very wide range of possible masses can be calculated by combining the radius with densities derived from the possible types of matter from which planets can be made. For example, it could be a rocky terrestrial planet or a lower density ocean planet with a thick atmosphere. A massive hydrogen/helium (H/He) atmosphere is thought, however, to be unlikely in a planet with a radius below 1.5 R⊕. Planets with radii of more than 1.5 times that of Earth tend to accumulate the thick atmospheres that would make them less likely to be habitable. Red dwarfs emit a much stronger extreme ultraviolet (XUV) flux when young than later in life. The planet's primordial atmosphere would have been subjected to elevated photoevaporation during that period, which would probably have largely removed any H/He-rich envelope through hydrodynamic mass loss.
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