| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco |
| Right ascension | 19h 02m 43.06139s[1] |
| Declination | +50° 14′ 28.7016″[1] |
| Apparent magnitude (V) | 11.157[2] |
| Characteristics | |
| Spectral type | G2V[3] |
| Astrometry | |
| Radial velocity (Rv) | −98.44±0.24[1] km/s |
| Proper motion (μ) | RA: −18.483mas/yr[1] Dec.: 41.382mas/yr[1] |
| Parallax (π) | 5.3698±0.0103 mas[1] |
| Distance | 607 ± 1 ly (186.2 ± 0.4 pc) |
| Details | |
| Mass | 0.910±0.021[2] M☉ |
| Radius | 1.065±0.009[2] R☉ |
| Temperature | 5708±28[2] K |
| Metallicity [Fe/H] | −0.15±0.04[4] dex |
| Age | 3.7–10.6+1.5 −1.3[2] Gyr |
| Other designations | |
| KOI-72,KIC 11904151,GSC 03549-00354,2MASS J19024305+5014286[3] | |
| Database references | |
| SIMBAD | data |
| KIC | data |
Kepler-10, formerly known asKOI-72, is aSun-like star in the constellation ofDraco that lies 607light-years (186parsecs) from Earth.[5][6] Kepler-10 was targeted byNASA'sKepler space telescope, as it was seen as the first star identified by the Kepler mission that could be a possible host to a small, transiting exoplanet.[7] The star is slightly less massive, slightly larger, and slightly cooler than the Sun; at an estimated 11.9 billion years in age, Kepler-10 is 2.3 times the age of the Sun.[2]
Kepler-10 is host to aplanetary system made up of at least three planets.Kepler-10b, the first undeniably rocky planet,[7] was discovered in its orbit after eight months of observation and announced on January 10, 2011. The planet orbits its star closely, completing an orbit every 0.8 days,[8] and has a density similar to that of iron.[7] The second planet,Kepler-10c, was confirmed on May 23, 2011, based on follow-up observations by theSpitzer Space Telescope. The data shows it has an orbital period of 42.3 days and has a radius more than double that of Earth, but it was initially thought to have a higher density, making it the largest and most massive rocky planet discovered as of June 2014.[2][9][10] However, refined mass measurements have shown it to be a more typical volatile-rich planet.[11] A third planet, Kepler-10d, was discovered in 2023 byradial velocity observations.[4]
Kepler-10 was named because it was the tenth planetary system observed by the Kepler spacecraft, a NASA satellite designed to search forEarth-like planets thattransit, or cross in front of, their host stars with respect toEarth. The transit slightly dims the host star; this periodic dimming effect is then noted by Kepler.[12] After eight months of observation ranging from May 2009 to January 2010, the Kepler team established Kepler-10b as the first rocky exoplanet discovered by the Kepler satellite. Kepler-10 was the first Kepler-targeted star suspected of having a small planet in orbit. Because of that, verifying Kepler's discovery was prioritized by telescopes at theW.M. Keck Observatory in Hawaii. The discovery was successfully verified.[7] Although there had been manypotentially rocky exoplanets discovered in the past, Kepler-10b was the firstdefinitively rocky planet to have been discovered.[13]
The discovery of Kepler-10b was announced to the public at a winter meeting of theAmerican Astronomical Society on January 10, 2011 in Seattle.[13] On May 23, 2011, the existence of Kepler-10c was confirmed at the 218th AAS meeting in Boston.[14]
Kepler-10 is aG-type star, like theSun. With a mass of 0.895 (± 0.06)Msun and a radius of 1.056 (± 0.021)Rsun, the star is approximately 10% less massive than and 5% wider than the Sun. Themetallicity of Kepler-10, as measured in [Fe/H] (the amount ofiron in the star), is -0.15 (± 0.04); this means that Kepler-10 is about 70% as metal-rich as the Sun. Metallicity tends to play a large role in the formation of planets, determining if they form, and what kind of planet they will form.[15] In addition, Kepler-10 is estimated to be 11.9 billion years old and to have aneffective temperature of 5627 (± 44)K;[5] To compare, the Sun is younger and hotter, with an age of 4.6 billion years[16] and an effective temperature of 5778 K.[17]
Kepler-10 is located at a distance of 186 parsecs from the Earth, which equates to approximately 607 light years. Also, Kepler-10'sapparent magnitude, or brightness as seen from Earth, is 10.96; it therefore cannot be seen with thenaked eye.[5]
Per the usualexoplanet nomenclature, the first planet discovered to be orbiting Kepler-10 is calledKepler-10b. Announced in 2011, it was the first definitelyrocky planet identified outside theSolar System. The planet has a mass that is 3.33±0.49 times that of Earth's and a radius that is 1.47+0.03
−0.02 times that of Earth.[2] The planet orbits Kepler-10 at a distance of 0.01684AU every 0.8375 days; this can be compared to the orbit andorbital period of planetMercury, which circles the Sun at a distance of 0.3871 AU every 87.97 days.[18] Because the planet orbits so closely to its star, itseccentricity is virtually zero. It, thus, has an extremely circular orbit.[8]
Kepler-10c[9] was also discovered by NASA'sKepler Mission,[19] the second exoplanet found to orbit Kepler-10. Radial-velocity measurements of the body initially suggested that it has a mass of 17.2±1.9 Earth masses and a radius of 2.35 Earth radii, which would have made it the largest known rocky planet as of 2014[update]. Kepler-10c would orbit Kepler-10 at a distance of 0.24 AU every 45.29 days.[2] However, in July 2017, more careful analysis of HARPS-N and HIRES data showed that Kepler-10c was much less massive than originally thought, instead around7.37+1.32
−1.19ME with a mean density of 3.14 g/cm3. Instead of a primarily rocky composition, the more accurately determined mass of Kepler-10c suggests a world made almost entirely of volatiles, mainly water.[11]
A candidate third planet with an orbital period of about 102 days, given the provisional designation KOI-72.X, was identified in 2016 based ontransit-timing variations.[20][11] In 2023, the presence of a third planet, Kepler-10d, was confirmed byradial velocity observations. It has an orbital period of 151 days and aminimum mass about 13 times that of Earth.[4]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 3.24±0.32 M🜨 | 0.01685±0.00013 | 0.8374907±0.0000002 | 0 | 84.8+3.2 −3.9° | 1.470+0.030 −0.020 R🜨 |
| c | 11.29±1.24 M🜨 | 0.2410±0.0019 | 45.294301±0.000048 | 0.121+0.035 −0.018 | 89.623±0.011° | 2.355±0.022 R🜨 |
| d | ≥13.00+0.73 −2.44 M🜨 | 0.5379±0.0044 | 151.09+0.18 −0.41 | 0.190+0.027 −0.070 | — | — |
Kepler-10 system | |
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