Kepler-70
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus[note 1]
Right ascension 19h 45m 25.47457s[1]
Declination +41° 05′ 33.8822″[1]
Apparent magnitude (V) 14.87[2]
Characteristics
Spectral type sdB[3]
Apparent magnitude (U) 13.80[2]
Apparent magnitude (B) 14.71[2]
Apparent magnitude (R) 15.43[2]
Apparent magnitude (I) 15.72[2]
Apparent magnitude (J) 15.36[2]
Apparent magnitude (H) 15.59[2]
Astrometry
Proper motion (μ) RA: 7.217(29) mas/yr[1]
Dec.: −3.148(30) mas/yr[1]
Parallax (π)0.9086 ± 0.0247 mas[1]
Distance3,590 ± 100 ly
(1,100 ± 30 pc)
Details
Mass0.496 ± 0.002[3] M☉
Radius0.203 ± 0.007[3] R☉
Luminosity (bolometric)22.9 ±  3.1 L☉
Temperature27,730 ± 260[3] K
Other designations
2MASS J19452546+4105339, KIC 5807616, KOI-55, UCAC2 46165657, UCAC3 263-170867, USNO-B1.0 1310-00349976.[2]
Database references
SIMBADdata
KICdata

Kepler-70, also known as KIC 5807616 and KOI-55, is a star about 3,600 light-years (1,100 parsecs) away in the constellation Cygnus, with an apparent visual magnitude of 14.87.[2] 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.

Properties

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

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 would have a temperature of about 7288 K,[10] the same as that of an F0 star. The hottest confirmed exoplanet and the hottest with a measured temperature is KELT-9b, with a temperature of about 4,600 K.[11]

The Kepler-70 planetary system[6]
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⊕
c (unconfirmed) 0.655 M⊕ 0.0076 0.34289 — 20–80, likely 65° 0.867 R⊕

Notes

  1. ↑ This is inferred from the RA and declination of the star.
  2. ↑ inclinations are derived from brightness variations and lack of transits.

References

  1. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. 1 2 3 4 5 6 7 8 9 "KPD 1943+4058". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 1 January 2012.
  3. 1 2 3 4 "Notes for Planet KOI-55 b". Extrasolar Planets Encyclopaedia. Archived from the original on 19 January 2012. Retrieved 1 January 2012.
  4. ↑ 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
  5. ↑ Cain, Fraser (4 February 2009). "White Dwarf Stars". Universe Today. Retrieved 8 January 2012.
  6. 1 2 3 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
  7. 1 2 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
  8. 1 2 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, arXiv:1906.03321, Bibcode:2019A&A...627A..86B, doi:10.1051/0004-6361/201835003, S2CID 182952925
  9. 1 2 3 jamesrushford (2013-10-22). "Kepler 70b: The Coolest Exoplanet". PC 120: Life in the Universe. Retrieved 2021-07-27.
  10. 1 2 3 4 5 jarrettkong (2013-10-23). "Kepler-70b: The Remnant of a Time Long Past". PC 120: Life in the Universe. Retrieved 2021-07-27.
  11. ↑ Jones, K.; Morris, B. M.; et al. (October 2022). "The stable climate of KELT-9b". Astronomy & Astrophysics. 666: A118. arXiv:2208.04818. Bibcode:2022A&A...666A.118J. doi:10.1051/0004-6361/202243823.
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