Watch transit of venus 2012

Tuesday, June 5 is the last chance in your lifetime to see the transit of Venus across the face of the sun.

The last transit of Venus happened in 2004, but the next won't be until 2117.

Venus won’t visibly pass between the Earth and the sun again until 2117, so get your special sun-viewing glasses now. In North America, the transit will start in the hours before sunset on June 5. Viewers in Asia, Australia, Africa and Europe can catch the transit at sunrise on June 6. The transit will begin at about 6:03 p.m. EDT, 5:04 p.m. CDT, 4:05 p.m. MDT and 3:06 p.m. PDT.

What is a transit of Venus?

When Venus passes directly between earth and the sun, we see the distant planet as a small dot gliding slowly across the face of the sun. Historically, this rare alignment is how we measured the size of our solar system. The view is like a front row seat to the transit method, by which we now find planets around distant stars.

Why so rare?

Transits of Venus are so rare because the planet must pass between earth and the sun while lining up vertically, as well.

Transits of Venus occur in pairs eight years apart separated by either 105.5 years or 121.5 years. The last Venus transit occurred in 2004, and the next pair won’t happen until 2117 and 2125. The reason transits are so rare is that Venus’ orbit is off-kilter from Earth’s orbit by about 3.4 degrees. That means that when Venus does pass between the Earth and the sun, it’s often too low or high to cross in front of the sun’s face.

“We tend to think of our solar system layout as perfectly organized with all the planets going around in the same direction all lined up,” Schneider told LiveScience. “The truth is that small amounts of misalignment matter a lot.”

There have been only seven transits of Venus since the invention of the telescope in 1610, according to NASA. They occurred in 1631, 1639, 1761, 1769, 1874, 1882 and 2004. [Gallery: Views of Venus]

Venus Transit of the Sun: A 2012 Observer’s Guide