| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cygnus[1] |
| Right ascension | 19h 47m 15.2874s[2] |
| Declination | +47° 31′ 35.665″[2] |
| Apparent magnitude (V) | 14.58 (± 0.02)[3] |
| Characteristics | |
| Evolutionary stage | subgiant[2] |
| Spectral type | F5IV[4] |
| V−Rcolor index | −0.31 |
| R−Icolor index | +0.87 |
| J−Hcolor index | 0.242 |
| J−Kcolor index | 0.266 |
| Astrometry | |
| Proper motion (μ) | RA: −1.469(22)mas/yr[2] Dec.: −6.768(20)mas/yr[2] |
| Parallax (π) | 0.4550±0.0168 mas[2] |
| Distance | 7,200 ± 300 ly (2,200 ± 80 pc) |
| Details | |
| Mass | 1.48[5] M☉ |
| Radius | 2.13[5] R☉ |
| Luminosity | 7.3[5] L☉ |
| Surface gravity (log g) | 3.89[6] cgs |
| Temperature | 5,999[6] K |
| Metallicity[Fe/H] | 0.17[6] dex |
| Rotation | 14.48 days[6] |
| Rotational velocity (v sin i) | 9.0[7] km/s |
| Age | 2.8[8] Gyr |
| Other designations | |
| KIC 10418224, 2MASS 19471528+4731357, KOI-428 | |
| Database references | |
| SIMBAD | data |
Kepler-40, formerly known asKOI-428, is anF-type star in the constellationCygnus. Kepler-40 is known to host at least one planet,Kepler-40b. The star is approximately 1.5 times more massive than the Sun, and is over two times its size; it was, at upon its discovery, the largest yet discovered with a transiting planet in its orbit.[3] Kepler-40 was first noted as home to a possible transiting object by theKepler spacecraft; the data on the system was released to the public. A team of French and Swiss scientists used follow-up data to determine the existence of theHot Jupiter planet Kepler-40b, and later had their results published in a scientific journal on January 4, 2011.
Kepler-40 was first targeted by theKepler spacecraft, an Earth-trailingNASA operation that searches for planets thattransit, or cross in front of, their host stars. It was labeled aKepler Object of Interest (KOI) during the satellite's first 33.5 days of operations, which stretched from mid-May to mid-June 2009, because of the detection of a potential transit event. The data collected by Kepler'sphotometer was publicly released, including data on Kepler-40 and its possible transiting companion.[3]
Data on Kepler-40 was analyzed by a team of French and Swiss astronomers, who first tested forfalse positives. When all obvious false positives were cleared, the science team used theSOPHIE échelle spectrograph at theHaute-Provence Observatory in southern France to gatherradial velocity measurements on the star. Collected data was then checked to see if it corresponded with that of a closely orbitingbinary star or that of a planet; it was found to be that of a planet, leading to the confirmation ofKepler-40b.[3]
After Kepler-40b was confirmed, the French and Swiss science team worked to clarify the stellar parameters its star by analyzing the star's spectrum as collected by SOPHIE. Kepler-40 is the sixth known planetary host star with aradius of more than 1.8 times that of the Sun.[3] At the time of its discovery, Kepler-40 was the most evolved star known to have a transiting planet.[3]
Kepler-40 and its exoplanet were published in the journalAstronomy and Astrophysics on January 4, 2011, after being submitted on September 15, 2010.[3]
Kepler-40 is anF-type star[3] that has 1.48 times themass of the Sun and 2.13 timesits radius.[5] The star has aneffective temperature of5,999 K,[6] making it hotter than the Sun. Itsmetallicity of [Fe/H] = 0.10 means that Kepler-40 has 1.26 times as much iron as the Sun does.[9]
Kepler-40 was, at the time of its discovery, the largest and most evolved star known to host a transiting planet. It is the sixth known host star with a radius over 1.8 times that of the Sun and a transiting planet, after stars that includeKepler-5 andKepler-7.[3]
Kepler-40 lies approximately 2200parsecs (7,200light years) away from Earth,[2] further than any star (with a known distance) with an exoplanet previously discovered by Kepler. With anapparent magnitude of 14.58, it was also dimmer than any star previously recognized by Kepler. Because of its low apparent magnitude, Kepler-40 cannot be seen with thenaked eye.[9]
Kepler-40b is the first (and only) planet discovered so far in the orbit of Kepler-40. It has amass that is 2.2 times that of Jupiter's, the rough equivalent of 700 Earths.[9] The planet also has a radius that is 1.17 timesthat of Jupiter and a density of 1.68 grams/cm3. Kepler-40b has anequilibrium temperature of 1620 K, over six times hotter than the equilibrium temperature of Earth. It orbits its star every 6.87 days at a distance of 0.081AU.[9]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 2.2 MJ | 0.081 | 6.8731697 | (0) | 85.47±0.94° | — |