Three Plus One = Four Planets At Dusk!

A dramatic trio of planets play tag with each other after sunset low in the west-northwestern sky during the last week of this month–along with a lone lovely planet in the southeastern one all month long. Here’s an opportunity to see the two innermost and fastest-moving planets bunched together with the largest of all such worlds, and across the evening sky the most beautiful planet in the entire heavens.

For nearly a week beginning on the evening of May 24 and extending into the 28th or so, Mercury and Venus, together with mighty Jupiter, will present a naked-eye and binocular spectacle above the sunset horizon some 45 minutes after sundown. While Jupiter slowly descends into the evening twilight all month long, Venus creeps upward towards it. And when they are having their close encounter, swift-moving Mercury joins the scene. While all three planets will be obvious to the unaided eye given an unobstructed horizon, they will be truly spectacular as seen together in binoculars, which will easily encompass all three of them in a single view. Their relative motion from evening to evening will be both obvious and thrilling, making it clear why the ancients called these restless worlds "planets" (Greek for "wanderers").

But there’s still more. Telescopes will show the differing apparent sizes and appearance of each planet, with Mercury’s and Venus’ partially illuminated disks contrasted with Jupiter’s nearly full one. And depending on when you look, you will see up to all four of the giant planet’s "Galilean" satellites (those discovered by Galileo with his primitive telescope) changing position about their host world from night-to-night. Should you be fortunate enough to own a low-power, wide-field telescope like the famed Edmund Astroscan-Plus with its amazing 3-degree apparent field of view (that’s 6 full-Moon-diameters of sky!), when closest on the evenings of the 26th and 27th the trio will easily fit within a single eyepiece field of view! What a truly wonderful and rare sight that promises to be!

Meanwhile, across the sky, Saturn graces the southeastern heavens at dusk during May and is highest in the south late in the evening. Its magnificent ring system is a beautiful sight in any optically sound telescope at magnifications of 25X or more. In the Scientifics 60mm refractor at 35X, its tiny image looks like an exquisite piece of cosmic jewelry! While the view in large amateur and observatory-class scopes is quite beyond any words to adequately describe, I still enjoy looking at Saturn’s crisp, tiny, and remote-looking countenance as seen at low power in a small telescope. Today, we’re all used to seeing this amazing other-worldly sight. But can you imagine how astounded the earliest stargazers were to come upon the sight of a ringed-planet? No wonder that many of them doubted both their eyes and their telescopes. You may well have too when you saw it for the very first time—I know I certainly did!

— James Mullaney
Former assistant editor at Sky & Telescope magazine & author of nine books on stargazing.