Kepler-20f
| Exoplanet | List of exoplanets | |
|---|---|---|
 |
||
| Parent star | ||
| Star | Kepler-20 (KOI-070) | |
| Constellation | Lyra | |
| Right ascension | (α) | 19h 10m 47.524s |
| Declination | (δ) | +42° 20′ 19.30″ |
| Apparent magnitude | (mV) | 12.51 |
| Distance | 950 ly (290±30 pc) |
|
| Spectral type | G8V | |
| Mass | (m) | 0.912±0.035 M☉ |
| Radius | (r) |
0.944+0.06 −0.095 R☉ |
| Temperature | (T) | 5466±93 K |
| Metallicity | [Fe/H] | 0.02±0.04 |
| Age |
8.8+4.7 −2.7 Gyr |
|
| Physical characteristics | ||
| Mass | (m) | ~1 M⊕ |
| Radius | (r) |
1.003+0.050 −0.089 R⊕ |
| Stellar flux | (F⊙) | 59 ⊕ |
| Temperature | (T) | 705 K (432 °C; 809 °F) |
| Orbital elements | ||
| Semi-major axis | (a) | 0.1104 AU |
| Eccentricity | (e) | <0.32 |
| Orbital period | (P) | 19.57706 d |
| Inclination | (i) |
88.68+0.17 −0.14° |
| Discovery information | ||
| Discovery date | 20 December 2011 | |
| Discoverer(s) | Kepler team | |
| Discovery method | Transit (Kepler Mission) | |
| Discovery status | Conference announcement | |
| Other designations | ||
|
2MASS J19104752+4220194 f, KOI-70.05, KOI-70 f, KIC 6850504 f
|
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| Database references | ||
| Extrasolar Planets Encyclopaedia |
data | |
| SIMBAD | data | |
| Exoplanet Archive | data | |
| Open Exoplanet Catalogue | data | |
Kepler-20f (also known by its Kepler Object of Interest designation KOI-70.05) is an exoplanet orbiting the Sun-like star Kepler-20, the second outermost of five such planets discovered by NASA's Kepler spacecraft. It is located approximately 950 light-years (290 parsecs, or about 8.988×1015 km) from Earth in the constellation Lyra. The exoplanet was found by using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. The planet is notable as it has the closest radius to Earth known so far.
Kepler-20f is very likely (>95% chance) a rocky planet because of its radius, which is notable as being the closet to Earth yet: 1.004 R⊕. However, although its radius is almost the same as Earth's, its surface conditions are not Earth-like in any way. The equilibrium temperature of Kepler-20f is approximately 705 K (432 °C; 809 °F), too hot to support liquid water on its surface and hot enough to melt some types of metal. But because of its size, it can be expected to have an atmosphere of water vapor. The mass of the planet can be approximated to around 0.66–3.04 M⊕, depending on its composition. An Earth-like composition would have its mass to be around 1.2 M⊕.
Kepler-20 is a Sun-like star in the constellation Lyra with a mass of 0.91 (± 0.03) M☉ and a radius of 0.94 (± 0.06) R☉, and is thought to be 8.8 billion years old, though there is a large uncertainty in its age. In other words, Kepler-20 is approximately 9% less massive and 6% shorter than the Sun. The star's metallicity is 0.01 (± 0.04), meaning that the level of iron (and, presumably, other elements) in the star is almost the same as that of the Sun. Metallicity plays an important role in planetary systems, and stars with higher metallicity are more likely to have planets detected around them. This may be because the higher metallicity provides more material with which to quickly build planets into gas giants or because the higher metallicity increases planet migration towards the host star, making the planet easier to detect. The star has four other known planets in orbit: Kepler-20b, Kepler-20c, Kepler-20d, and Kepler-20e. All of the planets in the system would fit inside the orbit of Mercury.
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