The gods smiled on Wisconsin yesterday

Posted by Rich Talcott
on Thursday, November 09, 2006

After abnormally cold and cloudy weather during September and October, November 8 saw mostly sunny skies and temperatures in the 60s. You couldn’t ask for better weather (in November, that is) to view Mercury’s transit of the Sun.

Mercury always seems so small when it crosses the Sun. With an angular diameter only 0.5 percent that of the Sun, the planet’s petite disk doesn’t come as a surprise. But Venus was only 6 times larger during its 2004 transit, and it appeared obvious without optical aid. You definitely needed a scope to spy Mercury.

Mercury appeared a lot smaller than sunspot 923, a massive solar storm that recently rotated into view. A quick comparison and calculation showed the spot had to be bigger than Earth — and that was just the dark umbra. Add in the lighter penumbra, and the spot easily spanned 20,000 miles. Two smaller spots near the Sun’s opposite limb seemed to be active, with nearby prominences visible through an H-alpha filter.

Despite its hours-long journey, Mercury’s transit seemed to be over all too quickly. Now we have to wait 10 years before seeing another one. Fortunately, a transit of Venus will punctuate the delay. On June 6, 2012, Venus will cross the Sun’s face for the last time this century. Let’s hope the weather gods will be smiling on us again.

Our friend and Birder's World Photo Editor Ernie Mastroianni created the animation above with images he captured from our parking lot.

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