March 19, 2010: When the sun sets on Saturday, March 20th, a special kind of night will fall across the Earth. It's an equal night.
Or as an astronomer would say, "it's an equinox." It's the date when the sun crosses the celestial equator heading north. Spring begins in one hemisphere, autumn in the other. The day and night are of approximately equal length.
To celebrate the occasion, Nature is providing a sky show.
It begins as soon as the sky grows dark. The Moon materializes first, a fat crescent hanging about a third of the way up the western sky. Wait until the twilight blue fades completely black and you will see that the Moon is not alone. The Pleiades are there as well.
The Moon and the Pleiades are having a close encounter of rare beauty. There's so little space between the two, the edge of the Moon will actually cover some of cluster's lesser stars. According to David Dunham of the International Occultation Timing Association, this is the best Moon-Pleiades meeting over the United States until the year 2023.
Right: A similar Moon-Pleiades conjunction photographed by Marek Nikodem of Szubin, Poland, in July 2009.
