Part 12 (1/2)

It never appears more than three hours after sunset, and as long before the sunrise, and is never more than forty-eight degrees from the sun.

MARS.

Mars is most like the earth of any of the planets, and, although not as interesting an object to view as the 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 Scorpius, and Aldebaran in Taurus, near which it frequently pa.s.ses.

The fixed stars, however, twinkle, while Mars glows steadily. If there is any doubt in the student's mind as to the ident.i.ty 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 pa.s.s through 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 perceptible 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.

Although Jupiter appears to move slowly, it really travels at the incomprehensible rate of five hundred miles a minute.

The most interesting feature about Jupiter for the amateur astronomer consists in observing four of its moons, which are visible with a small telescope. They appear like mere dots of light, and their transit of or occultation with the planet (that is, their disappearance before or behind its disk) can be watched, and is a never failing source of pleasure. A large telescope alone reveals Jupiter's four other moons.

SATURN.

Saturn is farther removed from the earth than any of the planets in the solar system, visible to the naked eye. It is distinguished from the fixed stars by the steadiness of its light, which is dull and of a yellow hue, though to some it appears to be of a greenish tinge. It seems barely to move, so slow is its motion among the stars, for it takes two and one half years to pa.s.s through a single constellation of the Zodiac.

Saturn has eight moons. t.i.tan, its largest one, can be seen with a 3”

gla.s.s. Its celebrated rings are telescopic objects but a small gla.s.s reveals them.

URa.n.u.s.

The student will hardly mistake Ura.n.u.s for a fixed star, as it is only under the most favorable circ.u.mstances that it can be seen with the naked eye.

At its nearest approach to the earth, it is as bright as a sixth-magnitude star. Ura.n.u.s is accompanied by four moons, and takes seven years to pa.s.s through a constellation of the Zodiac.

NEPTUNE.

Neptune is the most distant of the planets in the solar system, and is never visible to the naked eye.

The earth comes properly under a discussion of the planets, but a description of it is hardly within the scope of this work.

Confusion in identifying the planets is really confined to Mars and Saturn, for Venus and Jupiter are much brighter than any of the fixed stars, and their position in the heavens identifies them, as we have seen before.

The following table of first-magnitude stars in the Zodiacal constellations confines the question of identifying the planets to a comparison of the unknown star with the following-named stars:

Castor and Pollux in Gemini.