Kepler-70
Kepler-70, also known as KIC 5807616 and formerly as KOI-55, is a star in the constellation Cygnus with an apparent visual magnitude of 14.87,[3] and is 4200 light-years away. This is too faint to be seen with the naked eye; viewing it requires a telescope with an aperture of 40 cm (20 in) or more.[4] A subdwarf B star, Kepler-70 passed through the red giant stage some 18.4 million years ago. In its present-day state, it is fusing helium in its core. Once it runs out of helium it will contract to form a white dwarf. It has a relatively small radius of about 0.2 times the Sun's radius; white dwarfs are generally much smaller.[5] The star may be host to a planetary system with two planets,[6] although later research[7][8] indicates that this is not in fact the case. If they are confirmed to exist, then the innermost planet has the highest temperature of any known planet.
The Kepler-70 system if confirmed | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus[1][note 1] |
| Right ascension | 19h 45m 25.4746s[2] |
| Declination | +41° 5′ 33.8820″[2] |
| Apparent magnitude (V) | 14.87[3] |
| Characteristics | |
| Spectral type | sdB[1] |
| Apparent magnitude (U) | 13.80[3] |
| Apparent magnitude (B) | 14.71[3] |
| Apparent magnitude (R) | 15.43[3] |
| Apparent magnitude (I) | 15.72[3] |
| Apparent magnitude (J) | 15.36[3] |
| Apparent magnitude (H) | 15.59[3] |
| Astrometry | |
| Proper motion (μ) | RA: 7.185±0.061[2] mas/yr Dec.: −3.134±0.060[2] mas/yr |
| Parallax (π) | 0.7850 ± 0.0314 mas[2] |
| Distance | 4,200 ± 200 ly (1,270 ± 50 pc) |
| Details | |
| Mass | 0.496 ± 0.002[1] M☉ |
| Radius | 0.203 ± 0.007[1] R☉ |
| Luminosity (bolometric) | 22.9 ± 3.1 L☉ |
| Temperature | 27,730 ± 260[1] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
| KIC | data |
Properties edit
Kepler-70 is an sdB (B-type subdwarf star with a temperature of 27,730 K,[9] equivalent to that of a B0-type star. It has a luminosity of 18.9 L☉,[10][9] a radius of 0.203 R☉, and a mass about half of that of the sun. The star was an evolutionary giant less than 20 million years ago.[10]
Kepler-70 is still fusing.[9][10] When it runs out of helium, it will contract into a white dwarf.[10]
Planetary system edit
On December 26, 2011, evidence for two extremely short-period planets, Kepler-70b and Kepler-70c, was announced by Charpinet et al.[6] They were detected by the reflection of starlight caused by the planets themselves, rather than through a variation in apparent stellar magnitude caused by them transiting the star.
The measurements also suggested a smaller body between the two candidate planets; this remains unconfirmed.
If these planets exist, then the orbits of Kepler-70b and Kepler-70c have 7:10 orbital resonance and have the closest approach between planets of any known planetary system. However, later research[7] suggested that what had been detected was not in fact the reflection of light from exoplanets, but star pulsation "visible beyond the cut-off frequency of the star." Further research[8] indicated that star pulsation modes were indeed the more likely explanation for the signals found in 2011, and that the two exoplanets probably did not exist.
If Kepler-70b exists, then it has a temp of 7288 K,[10] the same as that of an F0 star.
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b (unconfirmed) | 0.440 M🜨 | 0.0060 | 0.2401 | — | 20–80, likely 65 [note 2]° | 0.759 R⊕ |
| d (unconfirmed) | — | — | — | — | — | — |
| c (unconfirmed) | 0.655 M🜨 | 0.0076 | 0.34289 | — | 20–80, likely 65° | 0.867 R⊕ |
Notes edit
References edit
- ^ a b c d e . Extrasolar Planet Database. Archived from the original on 19 January 2012. Retrieved 1 January 2012.
- ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c d e f g h i "KPD 1943+4058". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 1 January 2012.
- ^ Sherrod, P. Clay; Koed, Thomas L. (2003), A Complete Manual of Amateur Astronomy: Tools and Techniques for Astronomical Observations, Astronomy Series, Courier Dover Publications, p. 9, ISBN 0-486-42820-6
- ^ Cain, Fraser (4 February 2009). "White Dwarf Stars". Universe Today. Retrieved 8 January 2012.
- ^ a b Charpinet, S.; et al. (December 21, 2011), "A compact system of small planets around a former red-giant star", Nature, 480 (7378): 496–499, Bibcode:2011Natur.480..496C, doi:10.1038/nature10631, PMID 22193103, S2CID 2213885
- ^ a b Krzesinski, J. (August 25, 2015), "Planetary candidates around the pulsating sdB star KIC 5807616 considered doubtful", Astronomy & Astrophysics, 581: A7, Bibcode:2015A&A...581A...7K, doi:10.1051/0004-6361/201526346
- ^ a b Blokesz, A.; Krzesinski, J.; Kedziora-Chudczer, L. (4 July 2019), "Analysis of putative exoplanetary signatures found in light curves of two sdBV stars observed by Kepler", Astronomy & Astrophysics, 627: A86, Bibcode:2019A&A...627A..86B, doi:10.1051/0004-6361/201835003, S2CID 182952925
- ^ a b c jamesrushford (2013-10-22). "Kepler 70b: The Coolest Exoplanet". PC 120: Life in the Universe. Retrieved 2021-07-27.
- ^ a b c d e jarrettkong (2013-10-23). "Kepler-70b: The Remnant of a Time Long Past". PC 120: Life in the Universe. Retrieved 2021-07-27.