Kepler-42
 Artist's impression of the Kepler-42 (KOI-961) system Credit: NASA | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus |
| Right ascension | 19h 28m 52.5688s[1] |
| Declination | 44° 37′ 08.990″[1] |
| Apparent magnitude (V) | 16.12[2] |
| Characteristics | |
| Spectral type | M5V[3] |
| Details | |
Rotational velocity (v sin i) | 2.9±0.4[3] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
| KIC | data |
Kepler-42, formerly known as KOI-961, is a
extrasolar planets, all of which are smaller than Earth in radius,[5] and likely also in mass.[citation needed
]
Characteristics
Kepler-42's mass is estimated to be 0.13 times that of the Sun, and a radius 0.17 times that of the Sun, just 1.7 times that of the
mas/yr.[3] Due to its small size and low temperature, the star's habitable zone
is much closer to the star than Earth is to the Sun.
Planetary system
The planetary system comprising three
hot Jupiters) resemble the moon systems of giant planets such as Jupiter or Saturn more than it does the Solar System
. Despite these planets' small size and the star's being one of the faintest stars in Kepler field with confirmed planets, the detection of these planets was possible due to the small size of the star, causing these planets to block a larger proportion of starlight during their transits.
Not all of the orbital parameters of the system are known. For example, as with all transiting planets that have not had their properties established by means of other methods such as the
radial velocity method, the orbital eccentricity
remains unknown.
Based on the orbits of the planets and the luminosity and effective temperature of the host star, the
Kepler-42 d would have an equilibrium temperature of about 280 K (7 °C),[7] similar to Earth's 255 K (−18 °C).[8]
Estimates for the known planets are in the tables below:
| Temperature comparisons |
Kepler-42c | Kepler-42b
|
Kepler-42d
|
Earth |
| Global equilibrium temperature |
728 K 455 °C 851 °F |
524 K 251 °C 483.8 °F |
454 K 181 °C 357.8 °F |
255 K −18 °C −0.4 °F |
| References:[7][note 2] | ||||
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| c | <2.06 M🜨 | 0.006 | 0.45328731±0.00000005 | 0 | — | 0.73±0.03 R🜨 |
| b | <2.73 M🜨 | 0.0116 | 1.21377060+0.00000023 −0.00000025 |
0 | — | 0.76±0.03 R🜨 |
| d | <0.9 M🜨 | 0.0154 | 1.86511236+0.00000075 −0.00000071 |
0 | — | 0.67+0.04 −0.03 R🜨 |
Notes
References
- ^ .
- ^ "Star: KOI-961 – 3 PLANETS". Extrasolar Planets Encyclopaedia. 2012-01-12. Archived from the original on February 8, 2012. Retrieved 2012-01-12.
- ^ S2CID 14889361.
- ^ S2CID 119325474
- ^ "KOI-961: A Mini-Planetary System". NASA Ames Research Center Kepler, A Search for Habitable Planets. NASA Ames Research Center Kepler. 2012-01-11. Archived from the original on 2012-03-14. Retrieved 2012-01-11.
- S2CID 38317440.
- ^ a b "Planet Equilibrium Temperature". Habitable Exoplanets Catalog. Planetary Habitability Laboratory at the University of Puerto Rico. Archived from the original on 24 August 2017. Retrieved 29 February 2012.
- ^ "Radiating Equilibrium Temperature". University of Wisconsin Marathon County - Department of Geology/Geography. Archived from the original on 3 September 2006. Retrieved 29 February 2012.
- ^ "How many exoplanets has Kepler discovered?". 2015-04-09. Archived from the original on 2010-05-27.