The Planetary Paradetesttest
Sunset reveals Jupiter high in the south, shining far brighter than any other object. The king of planets is truly massive — more than twice as large as all the other planets combined. That’s a lot of reflective surface, which makes up for its distance from the sun. While more than three times as far from the sun as its inner neighbor Mars, Jupiter is second in brightness only to Venus. And despite its huge girth, Jupiter spins faster than any other planet, so that one Jovian day is less than 10 Earth hours.
As darkness settles, scan the southwest horizon for another bright planet, fleet Mercury. The next two weeks will be its best evening appearance until spring. The innermost planet, Mercury never strays far from the sun, and even then it never climbs more than 15 degrees above the horizon and never lingers for more than an hour or so. Unlike the other planets, which appear for months, even seasons at a time, Mercury’s appearances are few and fleeting. Yet the planet outshines all but the brightest stars. Of all the planets, Mercury spins the slowest, taking two Earth months to complete one rotation.
Mars, too, hovers above the southwest horizon immediately after evening twilight. You may need binoculars to pick out the red planet, several times dimmer than Mercury, from twilight’s haze.
Rising in the east at 4am, Saturn fills the sky’s planetary void. Almost twice as far from the sun as Jupiter, Saturn appears at first blush as a typical star. But with even a modest telescope, Saturn’s rings come into view as well as some of the larger of its 25 known moons.
Venus rises an hour after Saturn, but there should be no mistaking this planet for a star; it is the single brightest celestial object other than the sun and moon. Midway between it and Saturn is the blue-white star Spica.