Every few generations, a rare window is opened to the heavens. In 1639 the eyes of a human first witnessed a spectacle that had not been possible to see before, and wouldn’t be seen again for another 122 years.
The planet Venus makes a transit across the backdrop of the Sun much like the Moon does during a solar eclipse. On a cycle that repeats every 243 years, there are a total of 4 times that you can see this event; however, these viewings come in specific pairs. The time between transits for each pair is a short 8 years. Each of those pairs is then separated by intervals of 105 ½ years and 122 ½ years.
At its distance from the Earth (approximately 27 million miles during the transit), Venus will appear only as a small black circle – far too small to block all the light of the Sun; however, this doesn’t diminish the visual impact of this event. On June 5, 2012, the transit of Venus will begin at approximately 4:02pm. Venus will continue to pass in front of the Sun, making it nearly half-way across before sunset. The next chance to view this transit won’t occur until 2117 – 105 years from now! Viewing the Sun requires special equipment, such as a solar filter or solar eclipse glasses. Other ways to view eclipses or transits of the Sun, including pinhole projection, can be found here.
The transit of Venus occurs when it reaches conjunction – the point in Venus’ orbit where it passes directly between the Sun and Earth’s orbit. Johannes Kepler was the first to predict this phenomenon and calculated the transit of 1631. Unfortunately, Kepler’s predictions weren’t accurate enough to pinpoint the proper viewing locations and times and were later revised by Jeremiah Horrocks. In 1639, Horrocks’ calculations would pay off as he became the first human to witness this rare celestial event. The orbits of Venus and Earth would not give another chance to view such an alignment for another 122 years.
The Clark Planetarium will be setting up a viewing location at the Gateway Mall near the Olympic fountain for the public. While the Clark Planetarium will have telescopes equipped with solar filters present, you can also purchase a pair of eclipse glasses from the Planet Fun store for only $1.95. Remember, no matter how you chose to view this event, NEVER look directly at the Sun!