(outer-most solar system planet)
Neptune is the outer-most known planet in the solar system.
Among the solar system planets,
it is most similar to Uranus,
having a slightly larger mass and a slightly smaller radius.
It has 14 moons, of which one, Triton, is substantial.
Triton has a retrograde orbit, suggesting it is a captured minor planet.
Pluto and Neptune have a 3:2 orbital resonance.
The only mission to near Neptune was Voyager 2 in 1989.
Among its observations was a spot on the surface analogous to Jupiter's,
Neptune's called the Great Dark Spot (GDS or GDS-89), a storm
in Neptune's atmosphere. Subsequent HST observation
has shown the spot disappeared and later has shown another such spot.
The term Neptune is also used for Neptune-like
extra-solar planets, specifically significantly larger than
Earth and smaller than Jupiter or Saturn,
and typically a gas planet, perhaps with other
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Referenced by pages:
astronomical unit (AU)
equilibrium temperature (Teq)
Gliese 436 b (GJ 436 b)
Kuiper Belt (K Belt)
late heavy bombardment (LHB)
moment of inertia factor
solar mass (MSun)
Outer Solar System Origins Survey (OSSOS)
supercritical fluid (SCF)
Transiting Exoplanet Survey Satellite (TESS)
trans-Neptunian object (TNO)
TW Hydrae (TW Hya)