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Pinedale Online > News > June 2012 > Venus to pass across sun June 5th and 6th
Venus to pass across sun June 5th and 6th
June 4, 2012

Sky watchers will have a rare opportunity to see the planet Venus move in front of the sun June 5th-6th. The upcoming transit by Venus will last for about 6˝ hours and can be seen from more than half of Earth's surface. However, the disk of Venus is tiny compared to the sun and not much will be seen. Depending on where you live worldwide, the transit of Venus will happen on June 5 or 6, 2012. If you live in the world’s Western Hemisphere (North America, northwestern South America, Hawaii, Greenland or Iceland), the transit will start in the afternoon hours on June 5. In the world’s Eastern Hemisphere (Europe, Africa, Asia, Australia or New Zealand), the transit will first be seen at sunrise or in the morning hours on June 6. The astronomical occurrence will be visible to Wyoming residents and predicted to happen from 4:00PM until 7:25PM on Tuesday, June 5th. The next transit of Venus across the sun won’t happen again until 2117, 105 years from now.

Transit of Venus: June 5, 2012
By astronomers Ron Canterna, University of Wyoming; Jay Norris, Challis, Idaho Observatory; and Daryl Macomb, Boise State University.

The apparent diameter of the sun is sufficiently large (1/2 degree) and the orbital planes of Earth and our sister planet Venus sufficiently similar, that Venus infrequently transits, or crosses in front of the sun, as seen from Earth. These transits occur in pairs separated by eight years, with the pairs currently recurring after gaps of 105.5 or 121.5 years -- a "twice in a human lifetime event" if one happens to be born in a lucky year. The last transit occurred June 8, 2004, and its paired event will occur June 5-6.

In the United States, the start of the transit will be visible June 5, weather permitting, just after 4 p.m. MDT, with time of greatest excursion onto the sun's disk around 7:25 p.m. During the transit the apparent diameter of Venus will be close to one arc minute, or about 1/30 of the sun's diameter.

A small telescope (mirror or objective lens just a few inches in diameter) combined with an eyepiece providing low magnification (about 10-40 times) are quite ample to study progress of the black disk of Venus against the bright sun.

However, maximum warning -- the most important and imperative piece of equipment -- is a solar filter to block 99.999 percent of the sun's light. Without this filter, just an instant of looking at the sun through even a small telescope (or binoculars) will result in severe and often permanent damage to the eye's retina (this happened to the author while viewing the sun emerging from total eclipse). DANGER! RISK OF BLINDNESS! DO NOT LOOK DIRECTLY AT THE SUN TO VIEW THIS EVENT!!

Alternatively, but using a similar solar filter (e.g., grade 14 welder's glass), the transit can be viewed without aid of a telescope, as Venus' apparent diameter will be comparable to large sunspots.

Historically, transits of Venus were employed to obtain an accurate measure of the distance between Earth and the sun through the method of parallax. The next pair of transits of Venus will take place in the next century, in 2117 and 2125.

Related Links
  • Transit of Venus - Wikipedia
  • Northern Rockies Skies for June - University of Wyoming
  • Transit of Venus: June 5–6, 2012 - Sky & Telescope
  • Pinedale Online > News > June 2012 > Venus to pass across sun June 5th and 6th

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