Dr. Jay Pasachoff, Williams College – Transit of Venus

Jun 4, 2012

In today’s Academic Minute, Dr. Jay Pasachoff of Williams College explains the rare transit of Venus taking place on June 5th.

Jay Pasachoff is the Field Memorial Professor of Astronomy, Chair of the Astronomy Department, and Director of the Hopkins Observatory at Williams College. He has taken part in expeditions to observe 59 solar eclipses, including 29 total eclipses, and the 2004 transit of Venus.  These expeditions carried out experiments to study the million-degree-temperature of the solar corona to better understand how the corona gets so hot. He holds a Ph.D. from Harvard University.

About Dr. Pasachoff

Dr. Jay Pasachoff – Transit of Venus

On June 5, we in North America will be able to see an exceedingly rare and wonderful astronomical event, a transit of Venus, when the planet Venus is silhouetted against the face of the Sun.  Many universities and groups of amateur astronomers will make it possible to see through their telescopes on that afternoon, since otherwise the Sun is too bright to stare at safely.  The whole six hours will be visible throughout the Pacific Region, including Hawaii and Alaska.  In the continental United States, the sun will set while Venus is still silhouetted against its disk.  Even without a telescope, a special, inexpensive solar filter or #14 welder’s glass would enable you to see a tiny dot, Venus, on the face of the sun.

The first transit of Venus to be observed was seen by only two people, Jeremiah Horrocks and his friend William Crabtree, in 1639.  Transits come in pairs separated by 8 years, with a gap of over 100 years between pairs.  Hundreds of expeditions were sent all over the world for the transits of 1761 and 1769, because observing them was the best way to find out how big the solar system is.  The most famous took Captain Cook to Tahiti.  Hundreds more expeditions went to observe the transits of 1874 and 1882.

My colleagues and I used a NASA spacecraft in 2004 to observe the transit.  About 20 minutes before Venus went entirely onto the Sun, we saw a lighted rim around its back edge, its atmosphere bending sunlight toward us.  On June 5, 2012, we will concentrate on observing that atmosphere.  We are treating this coming transit as local truth for interpreting the transits now being observed of hundreds of planets around other stars.

Don’t miss seeing the June 5 transit, or else you would have to wait over 105 years, until 2117, to see the next one.