SKYLIGHTS

Astronomy news for the week starting Friday, October 23, 1998.

The Moon passes through its first quarter this week on Wednesday the 28th as it moves through the dim stars of the constellation Capricornus. It also moves slightly closer to us on its elliptical orbit, though the effect of changing distance is not visible to the eye.

Planetary news takes place at opposite ends of the week and at opposing ends of the Solar System. Saturn, a billion miles from the Sun and the last of the planets known since ancient times, has been encroaching heavily on the evening skies. On Friday the 23rd, the planet will pass opposition with the Sun, when it will rise at sunset, cross the meridian to the south at midnight, and set at sunrise, the planet now having its greatest retrograde, or westerly, motion against the starry background. Though technically in the constellation Pisces, it is very close to the point at which Pisces, Aries, and the non-zodiacal constellation Cetus all meet.

Cetus, the celestial whale or sea monster, is part of the Perseus myth, hero Perseus slaying the beast before he could devour the Princess Andromeda. Andromeda's mother, Queen Cassiopeia, a "W" shaped set of stars, is now climbing the northeastern sky in the evening, the stream of stars that represents Perseus not far behind. Pegasus, Perseus's flying horse, is represented by a prominent large square of stars that crosses the sky high to the south about 10 PM standard time (to which we will return this Sunday). Cetus, though dim and hard to find, contains one of the most famed stars of the sky, the great red long period variable Mira, which makes a naked-eye appearance for a time about once a year. The still-faint but slowly brightening star is about 10 degrees south-southeast of Saturn.

Jupiter, of course, remains the most prominent body in the sky outside of the Sun and Moon, its great distance offset by a huge size that reflects a great deal of sunlight. Curiously, both Jupiter and Saturn produce considerable energy on their own, the result of slow gravitational contraction and the condensation of internal helium that is mixed with their dominant hydrogen. If the Sun were turned off, both planets would disappear from visual view (as would the other planets), but would remain bright to our radio telescopes.