78 Planet Uranus

Uranus was the first planet found with a telescope. Uranus was discovered by Sir William Herschel in 1781, even though others might have recorded Uranus prior to Herschel and not realized what they were seeing. Uranus is often referred to as Neptune’s twin, because of similarities in their sizes, colors, and other characteristics.

Uranus rotates on its side. It is believed that this odd rotation is due to a collision with its moon Miranda. The planet shows little atmospheric activity, and actually looks like a green billiard ball. If Uranus has a core at all, it is a very small rocky core.

In its atmosphere, Uranus has more water, ammonia, and methane ices in its atmosphere than Jupiter and Saturn; so it is often referred to as an Ice Giant . It is the coldest planet in the solar system. Like Jupiter and Saturn, Uranus also exhibits aurora activity. The planet has 13 rings, composed of dark particles made of dust to less than a meter in diameter. Uranus has 27 known moons (as of August 2014); not as many as Jupiter or Saturn, but definitely its own system of worlds which orbit the planet.

Uranus at a Glance

Characteristics to Compare


  • Hydrogen (H ), Helium (H ), Methane (CH ), Ammonia (NH ), Water (H O)


  • Short rotation — 17.3 hours retrograde (backwards)


  • Long revolution — 84.01 years


  • An intricate system of rings:
    • 13 rings total; first 9 found via airborne telescope

Magnetic Field

  • Yes, tilted about 45 . Reason for tilt unknown

Uranus Satellite of Distinction — Chevron; is this possible tectonic activity? Probably collided with Uranus.

Image of Planet Uranus, looks like a billiard ball.
Image of the planet UranusPublic Domain | Image courtesy of NASA.

Image of Black and white image of Uranus, showing its rings and small circular moons called sheepherder moons.
Rings and Sheepherder moons (in circles)Public Domain | Image courtesy of NASA.

Image of Miranda, shows a whitish chevron or check mark on the lower right of the moon.
MirandaPublic Domain | Image courtesy of NASA.


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Introduction to Astronomy Copyright © by Lumen Learning is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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