Page:The Music of the Spheres.djvu/246

 are as bright as first magnitude stars, although Saturn is not so easy to find unless its location is definitely known. Venus is a very white star, Jupiter a bright yellow, Saturn a pale orange, and Mars a fiery red. Mars wanders farther south than any other planet seen in the evening skies. Mercury may sometimes be seen after sunset in the spring or before sunrise in the fall, but only for a few days at a time and hence will seldom be seen by one who does not know just when, as well as where, to look for it. Uranus and Neptune are too far away and the planetoids too small to be of much interest to amateurs.

If examined with a glass the planets will show a bright round disk while a star is no more than a point of light. Mercury and Venus show phases just as our moon for their orbits lie between the earth and the sun. Venus is particularly beautiful as a crescent and is best seen in the west near the setting sun. Jupiter ranks second in popularity for even a field-glass discloses his round shining face and four of his principal moons.

Between Mars and Jupiter lies an immense lane of over 300,000,000 miles. This lane had been considered vacant until a century and a quarter ago, and since it was an exception to the general law of planetary distances, it had long been of interest to astronomers. Mercury, Venus, Earth and Mars are distant 35,750,000; 66,750,000; 92,500,000 and 141,000,000 miles, respectively, from the sun; then came this wide vacancy, with the order for the distances between the planets again resumed beyond Jupiter. When the great Kepler suggested that there must be an invisible planet revolving in this gap, many thought that the idea was only a dream of a great mind, for a planet so close would have been discovered