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Why is Uranus blue-green in color?
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Uranus
Two views of the southern hemisphere of Uranus, produced from images obtained by Voyager 2 on Jan. 17, 1986. In colours visible to the unaided human eye, Uranus is a bland, nearly featureless sphere (left). In a colour-enhanced view processed to bring out low-contrast details, Uranus shows the banded cloud structure common to the four giant planets (right). From the polar perspective of Voyager at the time, the bands appear concentric around the planet's rotational axis, which is pointing nearly toward the Sun. Small ring-shaped features in the right image are artifacts arising from dust in the spacecraft's camera.
Uranus appears blue-green in color primarily due to the presence of methane in its atmosphere.
While the planet's atmosphere is composed mainly of hydrogen and helium, methane molecules are highly effective at absorbing red wavelengths of sunlight. Because the red portion of the light spectrum is filtered out by this absorption, the light reflected back to observers is dominated by the blue-green wavelengths, giving the planet its characteristic hue.12