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May 2007 Feature: Venus Flirts with the Midnight Hour

If the Earth's rotational axis stood upright as our planet revolved around the sun, the planet Venus at its greatest elongation from the Sun would never stay out a lot longer than 3 hours after sunset (9 p.m. local time), or rise much earlier than 3 hours before sunrise (3 a.m. local time). Because the Earth's rotational axis tilts some 23.5 degrees out of vertical, however, it's indeed possible for Venus to stay out past midnight, or to stay up all night long. But this intriguing phenomenon can only happen at far northern or southern latitudes.

At the end of the first week of May, Venus will be shining north of the June solstice point in the sky (at the border of the constellations Taurus and Gemini). At a declination of 26 degrees north of the celestial equator, Venus is primed to turn into a night owl at far northern outposts. At the latitude of Newcastle, England (55 degrees north), and Moscow, Russia (56 degrees north), Venus stays up till after the midnight hour. At the latitude of Fairbanks, Alaska (65 degrees north), Venus stays up all hours around the clock - like the Arctic midnight Sun of summer.

If you want to know how late Venus stays up in your sky, take a gander at sky almanacs offered by Old Farmer's Almanac or the US Naval Observatory. Remember, the clock probably won't tell you the true time of midnight, especially if you're on daylight savings time. Check the US Naval Observatory site for the Sun's transit time. Transit time refers to true solar noon, or midday. The middle of the night comes about 12 hours before or after midday.

Venus is famous for its 8-year cycles. Eight years from now, in May of 2015, there will be a repeat performance.

May Blue Moon

In the Americas, the month of May will feature two Full Moons. The second of two Full Moons to fall in the same calendar month is popularly called a Blue Moon. For more on the subject, read Earth & Sky's Tonight's Sky for May 1, 2007.

copyright 2007 by Bruce McClure

April 2007 Feature * June 2007 Feature