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This Week’s Sky: May 20 – 27

A quartet of planets span the sky from dusk to dawn.

M5 by Ron Brecher

The evening sky features several fine globular star clusters, including this one, M5 in Serpens. Courtesy Ron Brecher

All Week

The view facing west-northwest, one hour after sunset.

The view facing west-northwest, one hour after sunset.

The evening sky features two planets—one nearing the end of its run, the other entering its prime. Mars shines at magnitude 1.7 low in the west-northwest at dusk. Although its steady, eastward motion ensures the red planet will remain visible for some time yet, it’s gradually losing ground to encroaching twilight. As Mars sinks into the horizon haze, brilliant Jupiter rises in the southeast. Gleaming at magnitude –2.6, the giant world is a wondrous telescopic sight—but wait until it’s had time to gain altitude before beginning your observing session. Jupiter is at its highest around 2:30 a.m., local daylight time. Rising shortly after midnight is Saturn. At magnitude 0.3, the ringed wonder easy to pick out from the rather dim stars of eastern Sagittarius. Saturn is at is best around 4:45 a.m., as morning twilight begins to noticeably brighten the sky. Last to appear is brilliant Venus. The magnitude –3.8, the morning “star” should be an easy find, but you’ll need an unobstructed east horizon because Venus comes up less than an hour before daybreak.

May 21

Mercury is in conjunction with the Sun today. The swift, innermost world will re-emerge in the evening sky next month.

May 23

Facing south-southeast at 2 a.m., EDT.

Facing south-southeast at 2 a.m., EDT.

This morning, as the waning gibbous Moon and Saturn rise, they’ll be separated by just over five degrees. If you have wide-angle binoculars—such as 7×50s—you’ll be able to take in both objects in a single view. Otherwise, you can simply enjoy the naked-eye scene.

May 26

The Moon is at last-quarter phase at 12:33 p.m., EDT.

Weekend Stargazer

M5 Finder Chart

Use this chart to locate globular cluster, M5. (Click on the image for a full-size version.)

The May 24 – 26 weekend features moonfree evenings suitable for deep-sky hunting. One object that’s currently well positioned is globular cluster M5, in the constellation Serpens Caput.

Locating M5 is a straightforward affair if you picture it as the westernmost point in an equilateral triangle that also includes the stars Alpha (α) and Mu (μ) Serpentis. Although not as famous as M13, in Hercules, M5 is actually a touch brighter—magnitude 5.7 versus 5.8. Indeed, M5 holds the distinction of being the brightest globular cluster in the northern sky! The Serpens cluster is, unsurprisingly, an easy binocular target, though the low magnification typical of binos makes all but a few globulars appear nearly stellar. Thankfully, M5 is conveniently parked next to a similarly bright star—5th-magnitude 5 Serpentis. The ready comparison makes the slightly fuzzy nature of the globular more obvious.

In a telescope M5 is a splendid sight—and the greater the aperture, the better the view. Although small instruments do a fine job with the globular, it’s hard to beat the light-gathering and resolution capabilities of a big scope. The most memorable view I’ve ever had of M5 was with a friend’s 17.5-inch Dob. The cluster was simply stunning, its luminous, tightly packed central knot enveloped in a spherical swarm of faint stars. Beautiful.

At SkyNews we love to read about your experiences and see your photos. You can share them with us by e-mailing [email protected].

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