Kepler-70

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Kepler-70
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus[1][note 1]
Right ascension 19h 45m 25s[1]
Declination +41° 5′ 34″[1]
Apparent magnitude (V) 14.87[2]
Characteristics
Spectral type sdB[1]
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
Distance 3849 ± 310[1] ly
(1180 ± 95[1] 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
2MASS J19452546+4105339, KIC 5807616, KOI-55, UCAC2 46165657, UCAC3 263-170867, USNO-B1.0 1310-00349976.[2]
Database references
SIMBAD data
KIC data

Kepler-70, formerly known as KOI-55, is a star 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.[3]

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.[4] The star is host to a planetary system with two planets, Kepler-70b and Kepler-70c.[5] The innermost planet has the highest temperature of any known planet known so far.

Planetary system[edit]

On December 26, 2011, evidence for two extremely short-period planets was announced. 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 confirmed planets; this remains unconfirmed.

Orbits of Kepler-70b and Kepler-70c have 7:10 orbital resonance and have the closest approach between planets of any known planetary system.

The Kepler-70 planetary system[5]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b 0.440 M 0.0060 0.2401 20–80, likely 65 [note 2]° 0.759 R
KOI-55.03 (unconfirmed) 0.222 M 0.0065  0.605 R
c 0.655 M 0.0076 0.34289 20–80, likely 65° 0.867 R

Notes[edit]

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

References[edit]

  1. ^ a b c d e f g h i "Notes for Planet KOI-55 b". Extrasolar Planet Database. Archived from the original on 19 January 2012. Retrieved 1 January 2012. 
  2. ^ a b c d e f g h i "KPD 1943+4058". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 1 January 2012. 
  3. ^ 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 
  4. ^ Cain, Fraser (4 February 2009). "White Dwarf Stars". Universe Today. Retrieved 8 January 2012. 
  5. ^ 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 

External links[edit]