Page:The Music of the Spheres.djvu/209

 by one observer as "pale orange, lilac and gray." Castor is equally interesting, for a 3-inch telescope resolves it into two brilliant stars. The spectroscope, making further discoveries, disclosed the fact that a companion whirls around the fainter component, completing its orbit in 3 days, while the brighter component also has a companion which completes its orbit in 9 days. These four stars, which form the star we call Castor, revolve in pairs about a common center of gravity, completing their period in about 900 years.

The Heavenly Twins claim a unique distinction—that of having a planet found at their feet; Sir William Herschel, an English astronomer, has the equally unique distinction of having found the planet. This planet was surely an odd and interesting thing for a mortal to discover for it is not only a gaseous globe 32,000 miles in diameter, but its pole points almost at the sun at one time in its 84-year journey, causing it to have 42 years of daylight and 42 years of night! This was the first planet added to the five known since antiquity and its discovery was a joyful surprise. The boundary line of the solar system was now greatly increased for Uranus travels in an orbit which lies at an average distance of 1,771,000,000 miles from the sun. In accordance with the ancient custom of naming the planets after the immortals on Mount Olympus, the planet was named Uranus, after the God of the starry sky.

A wonderful star cluster was later discovered also at the feet of the Twins,—a little northwest of the feet of Castor. This is designated at 34M on star-maps and may be located in the sky even with a field-glass.

Castor and Pollux may be found a little south of the zenith during the evenings of February and March. Castor, which is the higher star, passes the meridian first, but Pollux, the brighter