Tomorrow, Venus will pass between the Sun and the Earth, a little black dot eclipsing the burning surface of the Sun. It will not do so again for another 115 years. Unless Ray Kurzweil is right and the singularity will have made us immortal time-travelers, we shan’t be seeing it again. Well, perhaps the youngest of Earth’s current inhabitants will.
Traditionally, transits of Mars and Venus were used to measure the solar system. With that work done, there was a surprise in 2004 when during Venus’s a glowing half-ring, or The Arc of Venus, was visible. The arc was only recently discovered and occurs as sunlight passes through a layer of Venus’s atmosphere. It can be seen from spacecraft and telescopes.
“The best times to look are ingress and egress–that is, when the disk of Venus is entering and exiting the sun,” advises astronomy professor Jay Pasachoff of Williams College. ”Ingress is between 22:09 and 22:27 UT on June 5th; egress occurs between 04:32 and 04:50 UT. Be sure your telescope is safely filtered. Both white light and H-alpha filters might possibly show the arc.”
Head over to NASA for more information on the Arc of Venus.