S&T contributing photographer Babak Tafreshi shot this photo of Venus transiting the Sun in 2004. (Click on the image for a high-res version.)

For most of North America, the transit of Venus will begin on the afternoon of June 5th and still be in progress at sunset. Those in western Pacific, eastern Asia, and eastern Australia see the whole show from beginning to end on June 6th (local date). (Click on the image for a high-res version.)

This close-up of Venus perching on the Sun's limb was shot using a webcam on a 16” Zeiss refractor, stopped to 12” with a solar filter. The very faint arc on the left side of Venus is probably due to sunlight refracting through the planet’s upper atmosphere. (Click on the image for a high-res version.)

Australian watchmaker F. Allerding recorded the “black-drop” effect as the silhouette of Venus prepared to exit the Sun’s disk on December 9, 1874. He observed through a 3½-inch refractor. Adapted from Observations of the Transit of Venus Made in New South Wales by Henry C. Russell (Sydney, 1892). (Click on the image for a high-res version.)

Transits of Venus can only occur when Venus passes between the Sun and Earth, a point on its orbit known as inferior conjunction. (Click on the image for a high-res version.)

This diagram shows how Venus's orbit around the Sun is inclined relative to Earth's orbit. The effect is exaggerated for the sake of clarity. Transits of Venus can only occur at the two nodes, where the orbital planes of Venus and Earth intersect. (Click on the image for a high-res version.)