Over the past few months, we've been showing people the brilliant white flare in our evening skies that is the planet Venus, Earth's closest sibling in both size and distance. On Tuesday, June 5th, that same bright planet will accomplish a rare feat, appearing for a few hours not as a bright spot on the nighttime sky, but as a dark spot in the daytime, silhouetted against the brilliant disk of the Sun.
The event is called the "transit of Venus" and not only is it a rare and beautiful wonder and been a pivotal historical event of great scientific significance, but Tuesday's is the last one any of us will ever see--except for, perhaps, some toddlers who are destined to live to ripe old ages.
So don't miss the chance to experience history on Tuesday, June 5, 3:04 PM to 9:46 PM PDT. Did I mention it's a rare event of historical scientific significance? And that it's your last chance to see it! Get it? If you own a toddler, make sure they see it.
You'll be glad you made the effort, as you'll then be members of a very exclusive club, one without membership dues. Since the invention of the telescope in 1608 there have been only seven transits of Venus, and Tuesday's will make eight. The transit of 1631 went unobserved and the 1639 event, the first ever observed, may have been seen by only two people. Talk about an exclusive club; more people have walked on the Moon.
For the 18th and 19th century transits of Venus, expeditions were sent out across the globe to observe Venus' path across the Sun -- including one led by Captain James Cook, in 1769. The observations were compared and used to triangulate the actual distance from the Earth to the Sun and by extension of scale to all the other planets in the solar system.
Not only is this phenomenon of historical scientific importance, it's even an opportunity for scientific investigation today. Tuesday's transit will be observed by researchers to refine techniques for detecting the presence of extrasolar planets (exoplanets): planets orbiting stars other than our Sun. Heck, there may even be an alien civilization who has detected the presence of Venus -- or the Earth for that matter -- by observing a transit.
So, now that I've convinced you not to miss Tuesday's transit of Venus, I suppose I should suggest some ways to actually see it. Fortunately, you have some options, even if you don't have a telescope or know how to use one to safely observe the Sun.
One way is through live public webcasts going on throughout the event. To name a couple, NASA Edge will be webcasting from Hawaii's Mauna Kea and from only a lava-bomb's-throw away, the Exploratorium will be feeding us a stream from Mauna Loa. From those volcanoes, chances of bad weather obstructing the view is minimal and from Hawaii the entire transit can be observed start to finish. (Whereas, here in Oakland, the Sun will set over an hour before Venus departs the sun's disk).
If you're looking for a public viewing party or event near you (that is, if you're not close enough to Chabot Space & Science Center to get here), check out NASA's Venus transit 2012 page and click on the "Event Locations" map.
At Chabot, we'll be doing it all. We'll have an array of safe-sun-viewing telescopes and their attendant experts on our Observatory Deck (weather permitting). We'll be viewing the live webcasts on the domes of our planetarium and theater. We'll have roving scientists on hand to answer your questions, enthusiastic volunteers and staff eager to maximize your historic experience and fun activities going on for the whole family. We expect crowds, so I recommend purchasing tickets in advance.
As for viewing the transit of Venus yourself, the most important advice I can give you is not to look at the Sun directly, with your eyes or with a telescope. This could result in permanent eye damage. There are safe methods for using a telescope to view the sun. One is by projecting the image of the sun onto a piece of paper. The other is by using a proper solar filter. If you are not thus equipped, find someone who is.