The transit of Venus across the disc of our sun tonight will mark the last time we will be able to see the astronomical event in our – relatively -- short lifetimes. It will be another 105 years before another Venus transit will be visible from earth.
The Venus transit will begin shortly after 3 p.m. PDT today, Tuesday, with the sun still fairly high in the sky, according to Ed Krupp, director of the Griffith Observatory in Los Angeles.
Krupp stated, “the sun will be fairly high. But the fun part is following it to sunset and seeing Venus gradually move across the disc of the sun.” He added, “You really want a view of the horizon that is not blocked by buildings or trees.”
The transit of Venus is an astronomical event similar to a solar eclipse except that the planetary outline of Venus will appear as only about 1/30th the diameter of the sun. The transit of Venus occurs when the planet crosses between the sun and earth, appearing as a tiny black dot against the bright backdrop of the setting sun.
Venus will reach the midpoint of its transit at around 6:25 p.m. PDT and will end at sunset in the continental United States. The entire transit will be visible in places like Alaska, Hawaii, Asia, the majority of Australia, New Zealand and eastern Africa. Countries in the Western Hemisphere will be able to see the transit at sunset Tuesday, those in the Eastern Hemisphere can witness the event at sunrise Wednesday.
Venus is not the only planetary body to make a transit across the sun. Mercury, with its close orbit to the Sun, transits every 13 to 14 years. The tilted orbit of Venus in comparison to the solar plane causes the transit of Venus across the sun to occur rarely. The next transit of Venus will not happen until the year 2117.
It is never recommended to look directly at the sun as Venus crosses it. Proper safety precautions should be taken as with any partial or total solar eclipse. Special glasses should be worn while witnessing the event as to protect the eyes from damage. No. 14 welder’s glasses can be purchased at welder’s shops or at home improvement stores. Special solar eclipse glasses can also be purchased and are designed to protect one’s vision from harm.
The transit of Venus can be watched online through the Space.com website.