Urunas
in astronomy, one of the superior planets between Saturn and Neptune. It was not known to the ancients. When Sir William Herschel, after the construction of his great reflecting telescope, was systematically examining with it all the stars above a certain magnitude, he, on March 13, 1781, found in the constellation Gemini a star which he recognized as having a disk which the others had not. He took it for a comet, and other contemporary astronomers held the same view. Its distance from the sun is about 1,800,000,000 miles, and it travels once around the orbit in about 87 years. It receives only URBAN about one three-thousandth part of the light and heat from the sun which fall on the earth. It is attended by at least four satellites-Ariel, Umbriel, Titania, and Oberon. Their orbits all lie in the orbits all all lie in the same plane, and are at right angles to the path of the planet itself -a circumstance not known in the case of any other planet. Called also Georgium Sidus and Herschel. See SOLAR SYSTEM .