Page:Field Book of Stars.djvu/140

118 more brilliant planets, Venus and Jupiter, it claims our attention chiefly because of the surmises respecting its habitability.

Mars appears to the naked eye as a bright red star, and when at a favorable opposition to the earth (which occurs only once in every fifteen years) it rivals Jupiter in splendor.

The planet may be mistaken for the first magnitude stars, Antares in ../Scorpio/, and Aldebaran in ../Taurus/, near which it frequently passes.

The fixed stars, however, twinkle, while Mars glows steadily. If there is any doubt in the student's mind as to the identity of the planet, a few nights of observation, noting the changes in the planet's position, will decide the point. It takes Mars about fifty-seven days to pass over one constellation in the Zodiac.

JUPITER.

Jupiter is the largest of all the planets in the solar system, and it is easily distinguished from the fixed stars because of its brilliancy and splendor, exceeding in brightness all the planets excepting Venus, and casting a preceptible shadow.

It moves slowly and majestically across the sky, advancing through the Zodiac at the rate of one constellation yearly. It is therefore a simple matter to forecast its position, for, in whatever constellation it is seen to-day, one year hence it will be seen equally advanced in the next constellation.