National Geographic News
An occultation of Venus by the moon.

Seen in a crescent phase, Venus (bottom) disappears behind the moon (file picture).

Photograph by Tom Fleming, Photo Researchers

Andrew Fazekas

for National Geographic News

Published August 13, 2012

Venus will play a disappearing act this afternoon as the bright planet slowly appears to slip behind the crescent moon.

Under clear skies, sky-watchers will be able to see the moon pass over Venus during what astronomers call an occultation.

Venus—which looks like a brilliant white star to the naked eye—will appear to wink out as it goes behind the moon and then reappear from behind the unlit side of the moon, which can't be seen in the daytime.

The Venus-moon occultation path first crosses eastern Russia, Japan, North and South Korea, and eastern China, where it will be visible just after sunrise.

The event will then be visible throughout most of North America, especially in the Pacific region.

In the U.S. West, sky-watchers looking southwest will see Venus duck behind the sunlit portion of the moon between 1:05 and 2:45 pm PT before the planet reappears on the unlit side between 2:20 and 2:50 pm PT.

The sky show will be most difficult to observe along the U.S. East Coast and the Gulf of Mexico, where the crescent moon will blot out Venus while the pair is sinking close to the western horizon in the late afternoon, between 4:35 and 4:55 pm ET.

(See "Transit of Venus 2012—Sun Show Will Be Last for a Century.")

How to See the Venus Sky Show

Because the Venus "eclipse" will occur in broad daylight, the biggest challenge for sky-watchers without a telescope will be to locate the moon. Binoculars will make the event much easier to witness, said Anthony Cook, astronomer at Griffith Observatory in Los Angeles, California.

"Once you find the moon, though, it will give your eye something to focus on, and you should find Venus to be surprisingly easy to see, as it is brighter ... than the moon," Cook said.

"Even though you won't be able to see the shape of Venus by unaided eye, you will be able to see it fade during the 30 seconds to 1 minute that it takes to disappear and appear.

"A telescope will additionally reveal the phase of Venus, which will be just shy of half-lit," he said.

Because of the relative positions of Venus and Earth in their orbits around the sun, Venus undergoes phases similar to those our moon.

Venus Eclipse Resembles Earthrise

On average there's a Venus eclipse visible somewhere on Earth every year.

(See "Venus Spinning Slower Than Thought—Scientists Stumped.")

"Through a telescope, seeing Venus over the cratered surface of the moon reminds me of the iconic Earthrise, as seen by Apollo 8," Cook said.

The next opportunity to see an occultation of Venus will be on September 8, 2013, in Chile and Argentina, while observers in North and Central America will get their chance on December 7, 2015.



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