Thursday, 31 December 2009

Blue Moon Tonight


In case you don't know it, there will be a blue moon - the first in 20 years - at 7.15pm tonight which should, cloud cover permitting, be viewable here in the Lancaster area. Not only that, there will be a partial lunar eclipse with the deepest eclipse at 7.22pm.

This eclipse of the Moon is partial, so only eight per cent of the Moon will actually be covered by Earth's shadow. However, quite a lot of the moon will appear to change colour.

Sadly, a blue moon isn't actually blue.The name reflects the relative rarity of two full moons in a month and is linked to the saying "once in a blue moon." Most years on average have 12 full moons, with one appearing each month.

We're told that the whole event is deeply significant astrologically, if not astronomically. The National Geographic notes that the last time a blue moon appeared was on New Year's Eve was in 1990, and it won't happen again until 2028.

NASA notes that while we won't see a blue moon tonight, it is possible for the Moon to appear tinged by a blue hue, sometimes caused by fine dirt circulating in the Earth's atmosphere, possibly from a volcanic explosion. The above picture is of our Moon taken was taken in a dark blue morning sky. The bright crescent is the only part directly exposed to sunlight - the rest of the Moon glows from sunlight reflected from the Earth. The planet Jupiter is also visible along with its four largest moons.

(With thanks to Jessica Abrahams. Image: Vic Winter, ICSTARS)

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