Community Corner

Watch Venus Transit the Sun Tuesday

Astronomers say the 2012 phenomenon won't be visible from Earth again until 2117.

A little after 3 p.m. on Tuesday, Lake Forest residents will have the opportunity to witness one of the rarest predictable celestial events: a transit of Venus.

After the sun and the moon, Venus—also known as the Morning Star or Evening Star—is the brightest natural object we can spot in the sky. As the second planet from the sun, Venus is closer to the sun than we are here on Earth.

A "transit" of Venus occurs when Venus passes between us and the sun in such a way that Venus' silhouette is backlit by the sun's rays. 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.

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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. (Many Southland residents recently got the chance to witness an eclipse: if you missed it, .)

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.

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Locally, assuming sufficiently clear skies, the transit will be visible starting at about 3:04 p.m. on Tuesday and will be visible in its entirety only from the western Pacific, eastern Asia, and eastern Australia and at high northern latitudes. It will take place on June 6 for skywatchers in the Eastern Hemisphere.

Scientific Importance of the Transit

Curious as to the scientific importance of the transit of Venus? Tammy Smecker-Hane, director of the University of California, Irvine, observatory, explains:

Astronomer Sir Edmund Halley first suggested that the distance to Venus could be determined by observing the timing of the transit of Venus from two, widely-spaced locations on the Earth using an effect known as parallax. That would then allow astronomers to estimate the size of our Solar System. Astronomers flocked to various places on the globe to view the transit of Venus in the 1760s, but their measurements were not good enough to do the job. Astronomers had to patiently wait for the transit of Venus in the late 1800s when the invention of cameras and photography finally made this measurement possible.

Even today, transits of planets across the faces of the stars they orbit are very important to astronomers because its one of the few way we can actually find planets in other solar systems. If the geometry of the orbit is just right, a planet will cross in front of its star, causing an observer to see the star's light dim by a small amount depending on the size of the planet. If the star is similar to the Sun, then it dims by 1 percent if the planet is similar in size to Jupiter or 0.002 percent if the planet is similar in size to the Earth. This is the only way astronomers can actually determine the radius of a planet.

However by also measuring the velocity of the planet and star as a function of time, astronomers can then determine the planet's mass and density, too, and find out whether its similar to a terrestrial planet like Earth or a gas giant like Jupiter. Therefore transits are a crucial way we study solar systems other than our own.

Watch the Transit From Home

The transit of Venus happens in pairs, every century; the last time it occurred was in 2004. Such an event has been observed in the modern era only six times previously.

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.

Never look directly at the sun with your naked eyes. You can damage your eyes. Likewise, viewing the sun with either binoculars or a telescope can direct the sun's magnified rays directly into your eyeball and cause serious injury―think about what happens to ants under a magnifying glass.

Sunglasses do not provide sufficient protection. If you know someone who works in plumbing or construction, ask them if they have any #14 welder's glass. You can look directly at the sun through this material without risking injury.

If you have a tripod or a partner and a pair of steady hands, you can use binoculars to project an image of the sun onto a white piece of paper. Remember, don't look through your binoculars at the sun!

If you want to join other Orange County residents to watch the event, the UCI observatory is hosting a viewing party from 3 to 9 p.m. Get driving directions to the observatory here.

Watch the Transit Online

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

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


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