High clouds in Juneau today (Tuesday) mostly obscured the roughly twice-a-century transit of Venus across the sun.
“If the sun was the size of a beach ball, Venus moving across the sun would be about the size of nickel,” Marie Drake Planetarium Director of Programs Ken Fix says, describing what could have been seen from Juneau, if there were no clouds blocking out the sun. “So, you’re actually going to be able to see it, even if you just use a filter and you don’t look through a telescope.”
Fix and other amateur astronomers from the planetarium were at Marine Park during most of the 7-hour transit, waiting for a break in the clouds. But alas, despite a few teases, the sun never made much of an appearance.
Venus actually comes between the Earth and the sun five times every eight years. But because their orbits are on different planes, Fix says Venus usually misses passing over the sun’s disk as seen from Earth.
“Venus’ orbit differs from ours by about three and a quarter degrees,” he says. “And it’s only when we lap each other, with Venus on the inside track on the same side of the sun, that we have the possibility of a transit. But we have to be on the same zero line reference to the sun. And that only happens every 105 or 113 years, depending on what part of the cycle we’re in.”
That means it won’t happen again until December 2117. Maybe the sun will be out in Juneau by then.