Kepler-9 is a G-type main-sequence star located 2,090 light years away from Earth in the constellation Lyra. It was discovered by the Kepler Space Telescope in 2010, and was the first system with multiple planets to be found by the transit method.
Nomenclature and history[]
The name "Kepler-9" comes from the Kepler Mission. It does not have a proper name.
In June 2010, about 43 days after Kepler came online, around 700 exoplanet candidates were submitted - Kepler-9 was one of those systems. It was found to be a multiplanetary system. Kepler-9 is the first system with multiple planets to have been found using the transit method. It is also the first planetary system where transiting planets were confirmed through transit timing variations method, allowing to calculate the masses of planets.
The discovery was announced on August 26, 2010.
Characteristics[]
Kepler-9 is very similar to our Sun, as it is a G2V type star. As such, it is nearly a solar twin, and contains a mass of 1.07 solar masses and a radius of 1.02 solar radii. It has nearly the exact same size and width. It has a temperature of 5777 K, one degree off the Sun's 5778 K, and is more metal-rich than the Sun (in terms of iron), by approximately 32%. It is also younger than the Sun, and is estimated to be around one billion years old.[1]
Planetary system[]
The system currently has three confirmed planets, all of which are in direct orbit. The closest one is Kepler-9d, while Kepler-9b is the second, with Kepler-9c following. Kepler-9d orbits extremely closely to the star, only taking 1.6 days to finish an orbit around the star. Kepler-9d is a super-Earth planet with a radius that is 1.64 times that of Earth.
It is thought that originally, Kepler-9b and 9c formed beyond the frost line, and migrated inward due to interactions with the remains of the protoplanetary disk.
| Planet | Mass | Semimajor axis | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 44.71 Earth mass | 0.142 AU | 19.247 days | 0.063 | 88.936° | 8.252 Earth radius |
| c | 30.79 Earth mass | 0.228 AU | 38.944 days | 0.067 | 89.180° | 8.077 Earth radius |
| d | N/A | 0.027 AU | 1.592 days | 0 | N/A° | 1.64 Earth radius |