# Kepler-46

Observation data Characteristics Epoch J2000      Equinox J2000 Artist's conception of the Kepler-46 system showing the two planets. Planet b transits its star, the same method by which it was detected. Constellation Lyra Right ascension 19h 17m 4.449s[1] Declination 42° 36′ 15.03″[1] Spectral type Unknown Apparent magnitude (H) 13.436[1] Apparent magnitude (K) 13.347[1] Distance 2795 ± 226 ly (857 ± 69 pc) Absolute bolometric magnitude (Mbol) 5.18 (predicted)[note 1] Mass 0.902 ± 0.04[2] M☉ Radius 0.94 ± 0.04[2] R☉ Temperature 5155 ± 105[2] K Metallicity [Fe/H] 0.41 ± 0.1[2][note 2] dex Age 9.9 +3.5-3.1[2] Gyr 2MASS J19170449+4236150, KIC 7109675[1]

Kepler-46, previously designated KOI-872, is a star located in the constellation Lyra. Observed since 2009 by the Kepler space observatory, it has since been found to possess a planetary system consisting of at least two planets and while it has a similar mass to the Sun (90%) it is significantly older at ten billion years.[2]

Kepler-46 b (previously KOI-872.01), was the first planet discovered in the system. It was found through detailed analysis of Kepler space observatory data. An additional planet, Kepler-46 c, was discovered by an outside group using Kepler public data through analysis of transit timing variations. While only one additional planet was confirmed by the analysis, the study revealed the potential existence of either an unconfirmed planet KOI-872.03 (KOI-872 d)[citation needed]. Validation by multiplicity method allowed to confirm the existence of this planet which was then renamed Kepler-46d.

## Planetary system

Planet b is a superjovian gas giant with 6 times the mass of Jupiter. The second planet in the system was among the first to be discovered through the method of transit timing variations, and through its confirmation of KOI-872 c with a 99% confidence level has shown that the method of detection may be used to detect future extrasolar planets and, possibly, extrasolar moons.[3] This second planet exerted a gravitational force on the first planet, orbiting its host star in just 34 days. While this usually occurs on an extremely regular schedule, additional planets within the system can disrupt the time of the transit, and these disruptions can indicate the presence of a planet, even if the disrupting planet does not pass in front of the host star itself.[3]

The data show that Kepler-46 c is an approximately Saturn-mass object with an orbital period of 57 days.[3] As the planet does not itself transit its host star, there is no way of knowing its size (probably a similar size to its sibling). The measurements also suggest the existence of another planet orbiting with a period of about 6.8 days, but this planet is unconfirmed.[2]

The method in which the planet was detected is similar to the way that the planet Neptune was discovered, in which the newly discovered planet is known by its pull on another which is already known to exist.[4]

The Kepler-46 planetary system[2]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
b <6 MJ 0.1967 ± 0.0029 33.60134 ± 0.00021 0.01 ± 0.01 0.812 ± 0.043 RJ
c 0.376 ± 0.023 MJ 0.2799 ± 0.0041 57.004 +0.091-0.1 0.01 ± 0.01
d 0.068 ± 0.003 6.76671 ± 0.00013 0.1513 ± 0.0089 RJ

## References

1. "Basic data: 2MASS J19170449+4236150". SIMBAD. University of Strasbourg. 2012. Retrieved May 16, 2012.
2. Schneider, Jean. "Notes for Star Kepler-46". Extrasolar Planets Encyclopaedia. Retrieved May 16, 2012.
3. ^ a b c Moskowitz, Clara (May 10, 2012). "Hidden Alien Planet Revealed by Its Own Gravity". Space.com. Space.com. Retrieved May 10, 2012.
4. ^ Crockett, Christopher (May 12, 2012). "New planet found in distant solar system by its tug on another world". EarthSky. Earthsky Communications. Retrieved May 19, 2012.

## Notes

1. ^ Figure based on the following equations, which calculated bolometric (total) luminosity across all spectra based on effective temperature: $m_{\rm star}=m_{\rm sun}-2.5\log_{10}\left({ L_{\rm star} \over L_{\odot} } \cdot \left(\frac{ d_{\rm sun} }{ d_{\rm star} }\right)^2\right)$ (cf. Luminosity) and $M = m_{\rm star} - 5 ((\log_{10}{D_L}) - 1)\!\,$ (cf. Absolute magnitude)
2. ^ This measurement indicates the log10 of the relative abundance of iron in the measured star to that of the Sun.