Page 49 - Curriculum Visions Dynamic Book

Although methane makes up only 2.3% of the Uranian atmosphere, the gas strongly absorbs red light. As a result, the planet reflects only the complementary colour from the colour spectrum. That is why it looks blue-green.
Uranus has a magnetic field that is positioned in a quite different place than the geographic poles, some 58° relative to the axis on which it spins.
As on Saturn, the rotation of the planet causes centrifugal forces to pull the gases away from a truly spherical (ball-like) shape, so that it is slightly flattened (by 2.2%) at the poles.
How can the composition of Uranus be explained? Because it doesn’t have a rock core
(or if it does, it is very small), it is unlikely to have captured gas to itself by gravity like the other planets. Rather, it seems to be the case that rocky and ice materials were captured by a planet that was made up of a ball of gases.
The atmosphere
Uranus has a thick atmosphere made up primarily of hydrogen and helium. There is a greater proportion of helium in the Uranian atmosphere than on Saturn or Jupiter. The lower part of the atmosphere also contains water, ammonia, and hydrogen sulfide.
The Uranian atmosphere is almost featureless, although winds are strong, and gases
move in parallel bands. They
were faintly detected in visits
by the Voyager spacecraft. However, although winds reach over 200 m/s,
Uranus does not appear
to be a stormy planet like Saturn or Jupiter.
atmosphere The envelope of gases that surrounds the Earth and other bodies in the universe.
axis (pl. axes) The line around which a body spins.
centrifugal force A force that acts on an orbiting or spinning body, tending to oppose gravity and move away from the centre of rotation.
complementary colour A colour that is diametrically opposite another in the range, or circle, of colours in the spectrum; for example, cyan (blue) is the complement of red.
core The central region of a body.
density A measure of the amount of matter in
a space.
false colour The colours used to make the appearance of some property more obvious.
gravity The force of attraction between bodies. magnetic field The region of influence of a
magnetic body.
orbit The path followed by one object as it tracks around another.
pole The geographic pole is the place where a line drawn along the axis of rotation exits from a body’s surface.
reflect To bounce back any light that falls on a surface.
rotation Spinning around an axis.
satellite An object that is in orbit around another
object, usually a planet.
voyager A pair of U.S. space probes designed to provide detailed information about the outer regions
of the solar system.
 The atmosphere of Uranus with a grid laid over it. This shows clearly how the atmosphere is arranged in latitudinal bands.
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