An Ancient Universe: How Astronomers Know the Vast Scale of Cosmic Time


This beautiful image of the planet Saturn was taken in August 1981 by the Voyager 2 spacecraft when it was 21 million kilometers from the planet. Saturn is one of the giant outer planets in our solar system, made mostly of liquid and gas. It has the most dramatic ring system among the four in our solar system. Such rings are made of large numbers of small icy and dusty pieces. Three of Saturn's icy moons (Tethys, Dione, and Rhea) are visible as small dots of light at the bottom of the picture. The shadow of Tethys can be seen under Saturn's rings. (Courtesy of the Jet Propulsion Laboratory/NASA)

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