Stargazers ready for last look at transit of Venus until 2117

Astronomers and stargazers will get a last chance to glimpse a rare astronomical event known as the transit of Venus starting Tuesday.

The phenomenon, which occurs when Venus's orbit brings the planet between Earth and the sun, takes place roughly twice a century -- the last transit was on June 8, 2004 -- and will not happen again until 2117.

Unlike in a solar eclipse, in which the moon temporarily obscures the sun, Venus will appear as a small black dot passing across the sun in the daytime sky. Spectators are advised to wear special solar eyeglasses, or dark, polarized lenses such as welder's glasses, to prevent eye damage.

Click here to learn more about Wayne State's viewing party

Richard Vondrak, deputy director of Solar System Exploration at NASA's Goddard Space Flight Center, said studying the event is "important in understanding our place in space." The transit of Venus was critical to the determination of Earth's distance from the sun, and thus the size of the solar system, Vondrak said. In the late 19th century, scientists finally ascertained the distance based on data from several transits, after a mathematician first proposed observing the transits back in 1663.

Viewers on the East Coast of the US can watch the transit of Venus with their protective glasses from 6:00pm ET until sunset, Vondrak said. Alaska and Hawaii are the only two states from which it will be possible to view the full transit.

-It can be viewed from most parts of the world, but not from Portugal or from big swaths of Spain, South America and Africa. From many parts of Europe, people will be able to view the latter part of the 6 1/2-hour transit after sunrise.

Vondrak said people can watch the transit without special glasses by tuning in to NASA's live webcast of the event from Mauna Kea, Hawaii, starting at 5:45pm ET.

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