The Solar System’s Famous Threesome

Ask someone to name the best-known planets and invariably Mars, Jupiter and Saturn will be the response. Indeed, the last two are the biggest such bodies in our solar system, while Mars—despite its diminutive size—is perhaps the most famous of all such worlds due to its long association with life elsewhere in the public mind. May evenings offer an opportunity to see all three at once. (Venus is sometimes also included, making a planetary foursome, but it’s currently a pre-dawn morning object and not visible in the evening sky.)

To find this threesome, go outside on a clear night about an hour after sunset and look first to the west where you’ll find Jupiter in Gemini, accompanied by that constellation’s two bright stars Castor and Pollux. Next face south, where about halfway up the sky in the constellation Virgo, ruddy Mars sits squarely on the celestial meridian (the imaginary north-south line in the sky passing overhead). Accompanying it to its lower left is Virgo’s bright star Spica, its bluish white hue contrasting nicely with Mars itself. Finally, turn to the southeast some distance from Mars and you’ll find Saturn positioned in the dim constellation Libra (which has no bright star to mark it). You can use your Scientifics Star and Planet Locator set for the time you’re observing to identify the above constellations. In each case, you’ll see a bright object not shown on the star chart that looks like “it shouldn’t be there”—it’s one of the wandering planets!
Even the smallest of telescopes will show Jupiter’s four bright Galilean satellites (those discovered by Galileo), depending where they are in their orbital dance about the planet. In fact, good quality 10x binoculars will reveal them when not too close to the glare of the planet itself. And while such glasses will show that Mars is not star-like in appearance, it takes a telescope to show it minute disk. Even though the planet was at opposition last month and therefore is currently relatively close to us, it’s not a favorable “flyby” of Earth this time. It’s apparent size in May is only about a third that of Jupiter, requiring a magnification for most eyes of around 100x to reveal its orange deserts, dark patches, and one of its polar ice caps.

The last member of our threesome is Saturn. If steadily held, 10x binoculars will show an egg-shaped blob—the blended image of the planet’s disk and rings. A telescope magnifying about 25x will just resolve the rings encircling the planet itself. I’ve been privileged over the years to have looked at Saturn through some of the largest telescopes in the world, and the views have been truly awesome! But there’s something alluring about seeing the ringed planet at such low power in a small telescope. To me, it appears like an exquisite piece of cosmic jewelry—too unearthly, too other-worldly, to possibly be real!

— James Mullaney
Former assistant editor at Sky & Telescope magazine & author of nine books on stargazing. His latest, Celebrating the Universe!, is available from HayHouse.com.