THE SURFACE OF URANUS

A lthough it was discovered with a telescope, Uranus only reaches a maximum brightness or magnitude of 5.5 and can be seen by the naked eye as a faint point of light on a very clear, dark night sky. Voyager 2 took many photos of Uranus that show it as being a featureless disk, except for some considerable darkening toward its edges.

U ranus's average distance from the Sun is 2.88 billion km (1.79 billion miles), and the planet takes about 84 Earth years to make one complete revolution about the Sun. Voyager 2 discovered that one day is generally 17.24 hours.

U ranus has an equatorial diameter of 51,100 km (31,750 miles), almost precisely four times that of the Earth, and a mass 14.58 times that of the Earth. Dark absorption bands were discovered in 1869 in the red part of the spectrum of Uranus. It was found to be methane gas in 1932. This red absorption is the major cause of the blue green color of the planet. The methane absorbs much of the red light from the impinging white sunlight, leaving a bluish green color in the reflected sunlight.

T he magnetic field of Uranus is very strong. This is shown by a well-developed magnetic tail that extends away from the Sun. Infrared measurements from Voyager 2 indicate that Uranus has an average temperature of -214 degrees C (-353 degrees F). Unlike the other giant planets, there is no evidence of any significant internal heat source

T he discovery on March 10, 1977, that Uranus has rings was one of the most unexpected and exciting events of modern planetary astronomy. Subsequent observations have indicated the presence of ten narrow rings of dark particles and one broad, diffuse ring. In addition there are 100 or more transient ringlets of dust-size particles, that were barely detected by the Voyager 2 images of the back lighted rings. Scientist believe the rings are geologically very young or else are frequently replenished by the breakup of small satellites.