Neptune
Planet Profile
Orbit: 4,504,000,000 km (30.06 AU)
from Sun
Diameter: 49,532 km (equatorial)
Mass: 1.0247e26 kg
Composition
(TFS) - Neptune's composition is probably similar
to Uranus': various "ices" and rock with about 15% hydrogen and a
little helium. Like Uranus, but unlike Jupiter and Saturn, it may not have a
distinct internal layering but rather to be more or less uniform in
composition. But there is most likely a small core (about the mass of the
Earth) of rocky material. Its atmosphere is mostly hydrogen and helium with a
small amount of methane.
Neptune's Composition
Neptune's
blue color is largely the result of absorption of red light by methane in the
atmosphere but there is some additional as-yet-unidentified chromophore which
gives the clouds their rich blue tint.
Like
a typical gas planet, Neptune has rapid winds confined to bands of latitude and
large storms or vortices. Neptune's winds are the fastest in the solar system,
reaching 2000 km/hour.
Like
Jupiter and Saturn, Neptune has an internal heat source -- it radiates more
than twice as much energy as it receives from the Sun.
At
the time of the Voyager encounter, Neptune's most prominent feature was the
Great Dark Spot (pic) in the southern hemisphere. It was about half the size as
Jupiter's Great Red Spot (about the same diameter as Earth). Neptune's winds
blew the Great Dark Spot westward at 300 meters/second (700 mph). Voyager 2 also
saw a smaller dark spot in the southern hemisphere and a small irregular white
cloud that zips around Neptune every 16 hours or so now known as "The
Scooter" (right). It may be a plume rising from lower in the atmosphere
but its true nature remains a mystery.
Great Dark Spot on Neptune
Voyager 2
However,
HST observations of Neptune (left) in 1994 show that the Great Dark Spot has
disappeared! It has either simply dissipated or is currently being masked by
other aspects of the atmosphere. A few months later HST discovered a new dark
spot in Neptune's northern hemisphere. This indicates that Neptune's atmosphere
changes rapidly, perhaps due to slight changes in the temperature differences
between the tops and bottoms of the clouds.
Neptune also has rings. Earth-based observations
showed only faint arcs instead of complete rings, but Voyager 2's images showed
them to be complete rings with bright clumps. One of the rings appears to have
a curious twisted structure (right).
Like Uranus and Jupiter, Neptune's rings are very dark
but their composition is unknown.
Neptune's rings
have been given names: the outermost is Adams (which contains three prominent
arcs now named Liberty, Equality and Fraternity), next is an unnamed ring
co-orbital with Galatea, then Leverrier (whose outer extensions are called
Lassell and Arago), and finally the faint but broad Galle.
Neptune's Rings
Neptune's magnetic field is, like Uranus', oddly
oriented and probably generated by motions of conductive material (probably
water) in its middle layers.
Neptune's
Satellites
Neptune has 14 known moons; 7 small named ones and
Triton , plus four discovered in 2002, one discovered in 2003 and S/2004 N1
discovered in 2013 by NASA.
Neptune's moons
SBB
source: http://nineplanets.org/neptune.html
