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K2-9 b is a Neptune-like exoplanet (an ice giant with a thick atmosphere), about 2.3 times the radius of Earth. With an equilibrium temperature of 314 K (41°C), it lies within the habitable zone where liquid water could potentially exist on its surface. The planet completes one orbit around its star every 18.4 Earth days. It was discovered in 2015 using the transit method. It orbits the M-type star K2-9, located approximately 83 parsecs (271 light-years) from Earth.
2015
Discovered
2.25
Earth Radii
314
Temperature (K)
Discovery Information
Discovery MethodTransit
Discovery Year2,015
Discovery FacilityK2
Orbital Properties
Orbital Period18.4498 days
Semi-Major Axis0.091 AU
Inclination87.983 deg
Physical Properties
Radius (Jupiter)0.2007 RJ
Radius (Earth)2.25 R⊕
Eq. Temperature314 K
Insolation Flux1.36 S⊕
Planetary Extremes
Where K2-9 b sits on the spectrum of all known exoplanets.
Radius2.25 R⊕
TinyEnormous
Temperature314 K
FrozenInferno
Year Length18.4 days
LightningGlacial
Star Distance0.091 AU
ScorchedFrozen exile
Star System View
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Size Comparison
2.25x Earth's radius (0.20x Jupiter)
Orbit Comparison
Earth: 365.25 days (1 AU)K2-9 b: 18.4 Earth days (0.091 AU)
Host Star: K2-9
Spectral TypeM2.5 V
Effective Temperature3,390 K
Mass0.3 M☉
Radius0.31 R☉
Size vs Sun3.23x smaller
Luminosity0.012 L☉
Luminosity vs Sun83.3x dimmer
Metallicity [Fe/H]-0.25
Distance (pc)82.9631 pc
Distance (ly)270.6 light-years
Planets in the K2-9 System
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