Sky Talk February 2012: Crescent Moon Visits Venus & Jupiter

Mark the evenings of February 25th and 26th on your calendar. If clear, head out after sunset and look toward the western sky. There you will see two of the brightest objects in the night sky—the planets Venus and Jupiter—being “sideswiped” by the brightest of all nighttime objects, the Moon. The spectacle will be readily visible with the unaided eye, and a truly fascinating sight in binoculars.

Other than a meteor shower, the occasional bright comet, or an eclipse, most people think of the sky as static and unchanging. But nothing could be further from the truth—everything in the sky is constantly in motion! The most obvious example of this is the slow movement of the stars from east to west due to the daily rotation of the Earth on its axis. And the very word “planet” comes from the Greek for “wanderers,” indicating that ancient skywatchers recognized that these bodies moved in relation to the stars themselves.

Venus and Jupiter are currently slowly drawing closer together each week as they prepare to meet in a spectacular celestial embrace (or “conjunction”) in March that will be covered in the next issue of Sky Talk. Most of this movement is due to Venus rapidly gaining altitude in the sky and catching up to Jupiter. On the evening of February 25th, Venus will be joined by the beautiful crescent Moon to its upper right. The following evening, the Moon will have moved upward (actually eastward in the sky) and to the right of Jupiter. The view on either of these evenings through your Edmund binoculars will be quite a sight! And should you have a rich-field telescope with a very wide field of view such as the Scientifics’ Astroscan Plus, both Moon and planet may actually fit in the same eyepiece field for a brief time. Whether using binoculars or telescope, be sure to notice the “Earthshine” illuminating the dark portion of the Moon itself. As discussed in past Sky Talk installments, this is sunlight from the Pacific Ocean where it’s still daylight reflecting back onto our satellite. (This glow is also visible to the unaided eye.)

Through a telescope at a magnification of about 30x, Venus will appear just over half-full (or slightly gibbous) during February. The best time to observe it is during twilight when the bright sky background cuts down on the glare from this radiant orb, which overpowers the planet in a dark sky. At the same magnification, Jupiter’s four bright Galilean satellites will be visible in constantly changing positions as they orbit the giant planet. And after it passes Venus and Jupiter, the Moon moves out of the scene in its never-ending eastward journey, clipping along at an orbital velocity of over 2,200 miles per hour. Truly, the heavenly canopy above us is not static but rather an ever-changing (and absolutely free) skyshow!

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


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