Venus to Make Final Passage Across Sun Until 2117

NNN--- VENUS MAKES RARE TREK ACROSS SUN. Another once-in-a-lifetime kind of transit of planet Venus (a planet crossing the face of Sun) started in Mabul Island, Sarawak, Malaysia on 6 June 2012 from 6.10am to 12.40pm. Size of planet Venus when viewed from Earth appeared to be a small black circle crossover on the surface of the Sun. The transit phenomenon has occurred in 1874 and 1882, and then in 2004 and 2012. One of the rarest astronomical events occurs, when the planet Venus passes directly between the Sun and Earth, which will only occur again on 2117. Photo courtesy images.bernama.com---NNN

Skywatchers around the world will have the chance to witness one of the galaxy's rarest astronomical events - Venus passing between the Sun and the Earth.

The six-and-a-half hour long passage begins Tuesday at 2209 UTC. Skywatchers on all seven continents will be able to view it - except for a large portion of South America and western Africa. 

Venus will appear as a small, black dot as it crosses in front of the Sun. However, experts warn to never look directly at the Sun - doing so can permanently damage eyesight or cause blindness. 

The passage will be shown on a number of websites including NASA's and the European Space Agency's.

Transits of Venus always occur in pairs, eight years apart, with more than a century separating each pair. 

Tuesday's transit bookends the 2004-2012 pair and will be the last time the phenomena occurs until 2117. The last passage occurred in 1874.

Beauty Spot on Sun: Transit of Venus on June 06, 2012. PIB Photo

Observations of transits in previous centuries allowed astronomers to calculate the distance between the Earth and the Sun - some 150 million kilometers. 

The Earth-to-Sun measurement gave scientists the final piece of information they needed to accurately determine the size of the solar system for the first time - and ultimately, the sizes and distances of everything in the cosmos. ---VOA News