Epoch J2000 Equinox J2000
|Right ascension||19h 45m 25s|
|Declination||+41° 5′ 34″|
|Apparent magnitude (V)||14.87|
|Apparent magnitude (U)||13.80|
|Apparent magnitude (B)||14.71|
|Apparent magnitude (R)||15.43|
|Apparent magnitude (I)||15.72|
|Apparent magnitude (J)||15.36|
|Apparent magnitude (H)||15.59|
|Distance||3849 ± 310 ly
(1180 ± 95 pc)
|Mass||0.496 ± 0.002 M☉|
|Radius||0.203 ± 0.007 R☉|
|Luminosity (bolometric)||22.9 ± 3.1 L☉|
|Temperature||27,730 ± 260 K|
Kepler-70, formerly known as KOI-55, is a star in the constellation Cygnus with an apparent visual magnitude of 14.87. 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.
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. The star is host to a planetary system with two planets, Kepler-70b and Kepler-70c. The innermost planet has the highest temperature of any known planet known so far.
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.
(in order from star)
|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⊕|
- This is inferred from the RA and declination of the star.
- inclinations are derived from brightness variations and lack of transits.
- "Notes for Planet KOI-55 b". Extrasolar Planet Database. Archived from the original on 19 January 2012. Retrieved 1 January 2012.
- "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.
- 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