Watch Venus in Transit Tonight

A little after 6 p.m. on Tuesday, residents of our area will have an opportunity to witness one of the rarest predictable celestial events: a transit of Venus.

Often referred to as the "Evening Star" or "Morning Star," Venus is the brightest natural object in our sky after the Sun and the Moon. As the second planet from the Sun, it's closer to the Sun than the Earth is. 

A "transit" of Venus occurs when Venus passes between us and the Sun in such a way that we can see Venus's silhouette backlit by the Sun's brilliant light. It last happened in 2004, but it won't happen again until 2117. Unless you plan to shatter some human longevity records, this is probably your last chance.

Were Venus either large enough or close enough to block out the Sun's light as it passed, we would call this event an eclipse, as we do when the Moon passes between the Earth and the Sun. Venus, however, is a little bit smaller than the Earth and about 27 million miles away. When its tiny silhouette is viewed against the Sun, which lies another 66 million miles beyond, it can offer viewers a dramatic sense of the solar system's vast scale.

Assuming sufficiently clear skies, the transit will be visible for us starting after 6 p.m. on Tuesday and will remain so until the sun sets. Those in the central and western U.S. will be able to enjoy it longer, while viewers in Alaska, Japan, and large sections of Australia, China, and Russia will be able to see it in its entirety. By the time the Sun rises on the East Coast on Wednesday, Venus will have completed the transit.

Here’s the scoop:

Facts about the transit of Venus

• According to NASA, Venus will cross in front of the sun at approximately 6:09 p.m. EDT on Tuesday, June 5, 2012.
• The event will last for seven hours.
• Transits of Venus first gained worldwide attention in the 18th century.
• The celestial event has been witnessed only seven times since the time of Galileo.
• This may be the last Venus transit of our lifetime; the next transit won’t take place until 105 years from now, in the year 2117.

How to view the transit of Venus

• Weather will determine if the transit will be visible to the naked eye. The current weather prediction from NOAA for our area is cloudy with a chance of showers.
• Viewers will be able to see Venus as a black dot moving across the sun.
• Do not stare at the sun. Venus will cover too little of the sun to block its blinding glare. 
• The safest way to view the transition is indirectly, using a pinhole projector.

Where to view Venus in transit across the sky

• Find a safe spot with a clear view of the night sky.

Though it's not quite the same as viewing the phenomenon in person, there are several places to watch the transit of Venus online:

• The Slooh Space Camera will offer an 8-hour webcast of the transit that includes real-time video feeds from 10 telescopes around the world.
• Astronomers Without Borders will carry a video stream of the transit from the Mount Wilson Observatory in California.
• NASA will offer a live video feed from Mauna Kea observatory in Hawaii with expert commentary.
• The San Francisco Exploratorium will host an online video stream from the Mauna Loa telescope in Hawaii.

Lastly, there's Don Pettit, an astronaut currently aboard the International Space Station. Pettit's not doing a video feed, but he will become the first person to ever photograph a transit of Venus from outer space.