LOS ANGELES >> It’s a spectacle that won’t repeat for another century — the sight of Venus slowly inching across the face of the sun.

So unless scientists discover the fountain of youth, none of us alive today will likely ever witness this celestial phenomenon again, dubbed a "transit of Venus."

It’s so unique that museums and schools around the globe are hosting Venus viewing festivities — all for a chance to see our star sport a fleeting beauty mark. Even astronauts aboard the International Space Station plan to observe the event.

The drama unfolds Tuesday afternoon from the Western Hemisphere.

Skygazers who want the full experience are flocking to Hawaii, considered one of the prime viewing spots since the whole transit will be visible. From the world-famous Waikiki Beach on Oahu to the summit of Mauna Kea on the Big Island, eclipse glasses will be passed out so that people can safely see Venus crossing without damaging their eyes.

Just remember to have patience.

"There’s no one big climactic moment. It takes longer to happen" than a solar or lunar eclipse, said Larry O’Hanlon, who does outreach at the W.M. Keck Observatory on the Big Island.

Venus will appear as a small black dot gliding across the disk of the sun. As in a solar eclipse, do not stare directly at the sun; wear special protective glasses.

The entire transit, lasting 6 hours and 40 minutes, will be visible from the western Pacific, eastern Asia and eastern Australia.

Skywatchers in the United States, Canada, Mexico, Central America, and the northern part of South America will see the beginning of the show before the sun sets. Europe, western and central Asia, eastern Africa and western Australia will catch the tail end after sunrise. Those who don’t want to leave their homes can follow live webcasts by NASA and various observatories.

"Anything silhouetted on the sun looks interesting. Seeing Venus is extremely rare," said astronomer Anthony Cook of the Griffith Observatory.

Perched on the south slope of Mount Hollywood in Los Angeles, the observatory is girding for heavy traffic Tuesday afternoon as throngs were expected to peer through telescopes with special filters set up on the lawn.

The second planet from the sun between Mercury and Earth, Venus is about the same size as Earth. It appears as one of the brightest objects in the night sky because its thick clouds reflect much of the sunlight back into space.

There will be no obvious change to the brightness of the sky during the event; Venus only blocks out a tiny fraction of the sun.

"You have to know it’s happening," said David DeVorkin, a senior curator at the Smithsonian’s National Air and Space Museum.

Venus is the third celestial show to grace the sky in less than a month. Just a day earlier, a partial lunar eclipse will be visible from western North America, South America, Australia and eastern Asia. And there was the much-hyped "ring of fire" solar eclipse on May 20.

Unlike eclipses, Venus transits are truly rare. They come in pairs, separated by more than 100 years. The last one occurred in 2004 and next pair in 2117 and 2125.

Since the German astronomer Johannes Kepler first predicted it in the 17th century, only six have been observed. The upcoming one will be the seventh.

Only two people were said to have seen the transit of 1639. The 1882 transit was a bigger deal — people jammed the sidewalks of New York City and paid 10 cents to peek through a telescope. John Philip Sousa even composed a score called "Transit of Venus March."

The one in 2004 was viewed by millions — in person and online.

University of Alabama astronomer William Keel was determined not to miss the 2004 transit, the first one in 122 years. But he only caught 45 minutes of the action before clouds rolled in. This time, he plans to set up telescopes on the roof and hopes for clear skies.

The early Venus viewings were a big deal to scientists who used the alignment to measure the size of our solar system. The technique is still used today to search for alien worlds outside our solar system.

___

Highlights of Bishop Museum’s Transit of Venus Festival on June 5

For Hawaii, the transit of Venus will start at 12:09 p.m. on June 5 and end at 6:42 p.m. Bishop Museum has planned a host of programs for the celestial event:

Planetarium  

>> During the festival the museum will offer showings of the full-dome show “When Venus Transits the Sun” (30 minutes) at 9:30 a.m., 11:30 a.m, 1:30 p.m., and 3:30 p.m. This planetarium show from Bays Mountain Planetarium explores the nature of the transit of Venus and covers the famous 1769 expedition of Captain Cook to observe the transit from Tahiti. 

>> The museum will also debut a new dome program called “Rekindling Venus” (22 minutes) which will show at 10:30 a.m. and 2:30 p.m. on June 5. Bishop Museum is taking part in the international debut of this program. “Rekindling Venus” is not primarily about astronomy but rather about the sea; the program immerses the viewer in the intricate, complex life of the marine environment. 

>> Also,  the live sky tour “The Sky Tonight” is scheduled for 12:30 and 4:30 p.m. (30 minutes) 

Talks

>> At 10:45 a.m. and 2 p.m., Michael Chauvin will present a talk titled “A Transit of Venus and a Transient Romance: Bernice Pauahi Bishop and Chester Smith Lyman.” Chauvin will discuss the 1874 transit of Venus from Hawaii, the topic of his Bishop Museum Press book “Hokuloa: The British 1874 Transit of Venus Expedition to Hawaii.” 

>> At 11:30 a.m. and 4:30 p.m., Gareth Wynn-Williams, professor of astronomy, Institute for Astronomy, University of Hawaii at Manoa, will discuss the transit. Wynn-Williams will discuss the history of transits of Venus overall, and provide an overview of the 2012 event. 

>> At 1:00 and 3:45 p.m., Paul Coleman of the Institute for Astronomy will give a talk on “Astronomy and the Transit of Venus in Hawaii”. Coleman will discuss how astronomy in general, and the transit of Venus in particular, are important in the history of Hawaii.

>> At 3:00 p.m., Peter Mouginis-Mark, of the Hawaii Institute of Geophysics and Planetology, UH-Manoa will talk about “The Geology of Venus.”

Also

>> Volunteers from the Hawaii Astronomical Society will be on campus from noon to 5 p.m. with their telescopes, to allow safe viewing of the transit through solar filters.

>> A  performance of John Phillips Sousa’s “Transit of Venus March” at 12:45 p.m.

>> “Venus: The World Beneath the Clouds” (20 min), a new program for Science on a Sphere, allows visitors to explore our sister planet Venus at 11 a.m., 1 p.m., and 3 p.m.  

Before June 5

In addition to the events on June 5, the museum will offer this additional programming in the run up to the transit:

>> Daily (except Tuesdays) from May 26-June 4: “When Venus Transits the Sun.” This full dome planetarium program about the transit will be shown at 2:30 daily except Tuesdays (30 minutes.) The program is included in regular admission to the museum.

>> Weekend of June 2-3: Special programming for the weekend before the transit. Programs are included in regular museum admission. The programs include: Staff from NASA Goddard’s Space Flight Center talk about the transit of Venus (at 1 p.m. at Atherton Halau); the planetarium show “When Venus Transits the Sun” at 11:30 a.m. and 2:30 p.m.; the Science on a Sphere program “Venus Below the Clouds” at 11 a.m., 3 p.m. and 4 p.m. 

———

Source: Bishop Museum

Online:

Transit details: http://eclipse.gsfc.nasa.gov/OH/transit12.html