Tuesday, October 04, 2005

Shirking my astronomical responsibilities

There was an annular solar eclipse ("annulus" = ring; at its most complete coverage the moon still had a ring of unblocked sunlight all around it) visible from much of Europe and Africa yesterday, particularly from Portugal and Spain. It had big write-ups in the October issues of Astronomy and Sky & Telescope. Unfortunately, with the way magazine subscriptions run I'm already looking for the December issues in my mailbox, and I had to dig quite a bit to find my October issues. I would have completely forgotten about this event - if I ever even knew about it in the first place - except that my friend in Ireland asked me about it. She had been reminded of it by her daughter about 12 hours after the eclipse itself.

My fault. I should have been crowing about it here, instead of talking about dryer maintenance and Supreme Court nominations.

Well, let me make it up to you. Eclipses tend to come in pairs - a solar followed about two weeks later by a lunar, or a lunar followed about two weeks later by a solar. (This has to do with "nodes" and the geometry of the orbits of the moon and the Earth, and I seem to recall that there may be exceptions.)* In this case, the lunar eclipse comes on October 17th (which is also the Full Moon - solar eclipses can only happen at New Moon, lunar eclipses can only happen at Full Moon.) It's a weak penumbral eclipse: the moon mostly passes through the outer edge of the Earth's shadow (the penumbra), and will pretty much just look a little dimmer and more colorful. My magazines say this will be visible from the western U.S., Australia and New Zealand, and (I presume) anywhere in between. So if you live in those parts, mark your calendars, and be sure to check your local listings for the exact time!

*I've fixed up the language here a little bit since I first wrote it. Here's what I originally said during my lunchtime post:
Eclipses come in clusters - I believe it's always a solar and a lunar in the same general time frame (it has to do with "nodes" and the geometry of the orbits of the moon and the Earth), although it may be two of one and one of the other.

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