Kepler-9b

Kepler-9b
	Size comparison of Kepler-9b (left) with Jupiter (right)
Discovery
Discovered by	Kepler Mission team
Discovery site	Kepler space telescope
Discovery date	26 August 2010
Detection method	Transit
Designations
Alternative names	KOI-377.01
Orbital characteristics
Semi-major axis	0.140 ± 0.001 AU (20,940,000 ± 150,000 km)
Eccentricity	0
Orbital period (sidereal)	19.24 d
Inclination	88.55
Star	Kepler-9
Physical characteristics
Mean radius	0.842 ± 0.069 RJ
Mass	43.5+2.7; −3.3 ME
Mean density	0.4±0.1 g cm−3

Kepler-9b is one of the first planets discovered outside the solar system (exoplanets) by NASA's Kepler Mission.^[1] It revolves around the star Kepler-9 within the constellation Lyra. Kepler-9b is the largest of three planets detected in the Kepler system by transit method; its mass is roughly half that of the planet Saturn, and it is the largest planet in its system. Kepler-9b and Kepler-9c display a phenomenon called orbital resonance, in which gravitational pull from each planet alters and stabilizes the orbit of the other. The planet's discovery was announced on August 26, 2010.

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