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How does Uranus's unusual tilt affect its seasons?

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Images obtained by Voyager 2. — 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 has an unusual axial tilt that causes it to spin nearly on its side, with its axis lying almost parallel to its orbital plane. This orientation significantly impacts the planet's seasons, as its poles take turns pointing directly toward the Sun as the planet completes its 84-year orbit.12

During this cycle, one pole may experience long periods of continuous sunlight while the other remains in darkness. For instance, when Voyager 2 visited in 1986, the north pole was in darkness, and the Sun was positioned nearly overhead at the south pole. Over the course of half a Uranian year—approximately 42 years—the Sun shifts its position until it is nearly overhead at the opposite pole.2

Despite these extreme variations in solar illumination, observations have shown that the temperature variation between the poles is surprisingly small, likely due to efficient horizontal heat transfer and the large heat-storage capacity of the planet's deep atmosphere.3