Live Chat: The 2012 Transit of Venus, with SA Editor George Musser

Musser, who covers space for SA, will help us prepare to watch Tuesday’s transit and explain the science behind this rare astronomical event

The 2012 Transit of Venus

Venus will pass in front of the solar disk on Tuesday, June 5. The next transit will not occur again until 2117, so don’t miss one of the rarest of sky shows

Join us below at 3 pm Eastern on Tuesday (June 5) for a live 30-minute online chat with SA Editor George Musser, who will discuss the transit of Venus occurring later that evening. We invite you to post chat questions in advance in the comments below.

On June 5 in the Americas and June 6 in the rest of the world, people will be able to see one of the rarest predictable events in astronomy: a solar transit of the planet Venus. Over a six-hour period the disk of Venus will be silhouetted against the sun. Seeing it safely requires a special eye-protection filter, or a telescope or binoculars can safely project an image onto a wall or sheet of paper. But if you miss it, your next chance won’t come until the year 2117.

Image: Flickr/NASA Goddard Photo and Video

Image: Flickr/NASA Goddard Photo and Video


Get the big picture:

Venus comes between Earth and the sun five times in the course of every eight years, but because of the inclination of the planets’ orbits, Venus usually misses passing over the sun’s disk, as seen from Earth. In fact, that passing-over phenomenon occurs only twice in the typical person’s lifetime. Two transits occur eight years apart, but each pair is separated by either 105.5 years or 121.5 years. We had a Venus transit in 2004, and we’re having another one today. The next one won’t come until 2117. So if you’re into rare sky phenomena, today is as good as it gets.


Find out when and where:

Venus’ disk begins to pass over the left edge of the sun’s disk a little after 6 p.m. ET, and makes a stately crossing that lasts until about 12:50 a.m. ET. (Of course, the sun will have set on the East Coast by then.) Some part of the transit will be visible from most locations on Earth — though you’re out of luck if you’re in eastern South America, western Africa, the Iberian Peninsula, Antarctica or the middle of the Atlantic.

The precise time when different edges of the planet’s disk cross the sun’s edge is actually a big deal. Those times vary by location on Earth, and the variations can be used to calculate dimensions and distances in the solar system. Today, so much is known about those dimensions that astronomers can predict the key times of the transit based on your location. To find out what you can see when, use the U.S. Naval Observatory’s transit computer.


Safe Solar Viewing

How to view the Sun safely for solar eclipses or to see sunspots or faculae on the sun’s surface. White light solar filters, solar projection options such as telescopic projection and pinhole projection, and unmagnified methods are all discussed. Unsafe ways to view the Sun are also part of the cautions presented, including the dangerous “eyepiece” solar filters that used to be part of many older telescope sets.


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