The Solar System

530 PART 4^ |^ THE SOLAR SYSTEM

■ Figure 24-3

Uranus rotates on an axis that is tipped
97.9° from the perpendicular to its orbit,
so its seasons are extreme. When one of its
poles is pointed nearly at the sun (a sol-
stice), an inhabitant of Uranus would see
the sun near a celestial pole, and it would
never rise or set. As it orbits the sun, the
planet maintains the direction of its axis in
space, and thus the sun moves from pole to
pole. At the time of an equinox on Uranus,
the sun would be on the celestial equator
and would rise and set with each rotation
of the planet. Compare with similar dia-
grams for Earth on page 24.

N

S

N

S

N

S

N

S

South

celestial pole

South

E celestial pole

W

NS

eC

les

tia

le

qu

at

or

E

W

NS

eC

les

tia

le

qu

at

or

Southern solstice

occurred in 1986.

Vernal equinox

occurred in 2007.

c

South pole

Cloud

Photographic

blemish

Enhanced visual image Enhanced visual image

a

Visual-wavelength image

b

■ Figure 24-4

(a) This Voyager 2 image of Uranus was made in 1986 and shows no clouds. Only when the image is computer enhanced, as in
(b), is a banded structure visible. At the time, the axis of rotation was pointed nearly at the sun. (c) Under extreme computer
enhancement, small methane clouds were visible. The geometry of the banding and the clouds suggests belt–zone circulation
analogous to that on Saturn and Jupiter. (NASA)