Space Station Info >> Physical Characteristics Of Uranus
Physical Characteristics Of Uranus
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Composition
Uranus is mainly composed of rocks and various
ices, with only about 15% hydrogen and a little
helium. Uranus (like Neptune) is analogous to
the cores of Jupiter and Saturn minus the substantial
liquid metallic hydrogen envelope. It seems that
Uranus does not have a hard core like Jupiter
and Saturn however that its material is more or
less equally
dispersed. Uranus' cyan color is due to the absorption
of red light by atmospheric methane.
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Axial
Tilt
One of the most typical features of Uranus is
its axial tilt of ninety-eight degrees. As a result,
for part of its orbit one pole faces the Sun frequently
even as the other pole faces away. At the alternative
side of Uranus' orbit the orientation of the poles
towards the Sun is reversed. Between these two
extremes of its orbit the Sun rises and sets around
the equator usually.
At the time of Voyager 2's passage in 1986,
Uranus' south pole was pointed about directly
at the Sun. Uranus can either be described
as having an axial tilt of slightly more than
90°, or it can be described as having
an axial tilt of some what less than 90°
and rotating in a retrograde direction; these
two descriptions are exactly correspondent
as physical descriptions of the planet but
result in different definitions of which pole
is the North Pole and which is the South Pole. |
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Magnetic
Field
Uranus' magnetic field is peculiar in that it
is not centered on the center of the planet and
is tilted about 60° with respect to the axis
of rotation. It is perhaps generated by motion
at relatively shallow depths within Uranus. Neptune
likewise has a displaced magnetic field, suggesting
that this is not necessarily a result of Uranus'
axial tilt. The magnetotail is twisted by the
planet's rotation into a long corkscrew shape
behind the planet. The magnetic field's source
is unknown; the electrically conductive, super-pressurized
ocean of water and ammonia once thought to lie
between the core and the atmosphere now appears
to be nonexistent.
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