Wednesday, February 22, 2006

What is that star?

"This is only the second time in my life I've seen Mercury," says sky watcher Jeffrey Beall who snapped this picture looking west from his balcony in Denver, Colorado.Mercury is the bright "star" just above the mountain ridge, rivaling the city lights.

Mercury makes a rare appearance in the evening sky this week.

"Mercury is elusive because it spends most of its time hidden by the glare of the sun. This week is different. From now until about March 1st, Mercury moves out of the glare and into plain view. It's not that Mercury is genuinely farther from the sun. It just looks that way because of the Earth-sun-Mercury geometry in late February. A picture is worth a thousand words: diagram.

Friday, Feb. 24th, is the best day to look; that's the date of greatest elongation or separation from the sun. Other dates of note are Feb 28th and March 1st when the crescent moon glides by Mercury—very pretty."

Other space stories can be read at Science@NASA.

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