The 'Evening Star' is Back: How to Spot Venus

Since last summer, the dominant evening planet was Jupiter, but that has now changed. As Jupiter sank deeper into the bright glow of evening twilight, Venus emerged.

Venus is closer to the sun than Earth, so its year — the time it takes to go around the sun — is much shorter than ours. As Venus circles the sun on the inside track, it alternates from our point of view from the morning sky to the evening and back.

After its last stint in the morning sky, Venus appeared to go behind the sun — what astronomers call "superior conjunction" — on Jan. 11. For weeks it was not visible, mired deep in the brilliant glare of the sun. Yet with each passing day, it has been moving on a slow course to the east, pulling away from the sun from our point of view.

Where to look

Now Venus hangs low in the western sky at sunset, an "evening star" that will rise higher each night. Anyone with a clear view of the western horizon can now spot Venus with the naked eye just after the sun sets and for about an hour thereafter, but finding it low on the horizon and amid the sun's fading glare could prove challenging.

By Feb. 28 the difference between sunset and Venus' setting will have improved slightly to 55 minutes, giving less-experienced sky watchers a fighting chance to get their first glimpse.

Continuing to swing east of the sun during March, Venus will soon become plainly visible in the western evening sky even to the most casual of observers. Appearing as a brilliant white starlike object of magnitude ?3.9, our sister planet will set at least an hour after the sun by March 4. On this magnitude scale, smaller numbers represent brighter objects, and Venus is the brightest natural object in the sky other than the sun and moon.

Venus slowly rises higher each evening to adorn the western evening sky all during the upcoming spring and summer. By the first week of June, it will be setting more than two-and-a-half hours after the sun. The planet's greatest altitude at sunset will also be occurring at this time.

Visits with other planets

From March 28 to April 12, Venus and Mercury will make for an attractive pair in the west-northwest sky soon after sunset.? Between these two dates these two planets are within 5 degrees of each other, Venus appearing to the left and slightly above the dimmer Mercury. (Your fist on an outstretched arm measures about 10 degrees of sky.) On April 3, they will appear closest together, just a little over 3 degrees apart.?

Then in early August, Venus will become part of a "planetary trio," joining much dimmer Mars and Saturn, low in the western sky right after sunset.

Venus reaches its greatest elongation — its greatest angular distance — 46 degrees to the east of the sun on Aug. 22.?

According to the 2010 Celestial Handbook of the Royal Astronomical Society of Canada, it will be brightest in early autumn as it heads back down toward the sun, reaching its peak brilliance for this apparition on Sept. 23 at an eye-popping magnitude of ?4.8.? That would make it 23 times brighter than Sirius, the brightest star. Venus then quickly fades, vanishing from view in mid-October, and passes inferior conjunction on Oct. 28.

Within a week it reemerges as a "morning star" in the southeast.

Going through phases

Many people don't realized that Venus goes through phases, much like our moon. Between now and October, repeated observation of Venus with a small telescope will show the complete range of its phases and disk sizes.?

The planet now appears practically full (99-percent sunlit), and will be a tiny, dazzling disk.?It will become more of a gibbous shape and a little larger in apparent size by late spring.?In late August, Venus reaches dichotomy (displaying a "half moon" shape).

Then, for the rest of the year it displays an increasingly large and thinning crescent as it swings nearer to Earth. Indeed, those using telescopes will note that while the Earth-Venus distance is lessening, the apparent size of Venus' disk will grow, doubling from its present size by July 31.

When Venus has doubled again in size on Sep. 23, its large crescent shape should be easily discernable even in steadily held 7-power binoculars.

• Venus Image Gallery
• Venus Images from Around the World
• Telescope Buying Guide

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.