Volume 16, Issue 24 - June 12 - June 18, 2008

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Sky Watch by J. Alex Knoll

Star Light, Star Bright

While we bask in the lengthening glow of our own star, those nighttime lights travel years to bring us their twinkle

Saturday’s sunrise at 13 seconds past 5:42 marks the earliest of the year. By solstice a week later on the 20th, the sun will already rise 40 seconds later. While summer solstice marks the longest day of the year, Earth’s less-than-spherical shape and its egg-shaped orbit around the sun separate earliest sunrise and latest sunset by about two weeks. Right now, Earth is at the sharp point of its orbit — the egg’s top. In winter, when Earth is at the shallow point in its orbit — at the egg’s bottom — nearly four weeks separate the latest sunrise from the earliest sunset.

As the sun sets around 8:35 this week, golden Saturn and blue-white Regulus appear in the southwestern sky, roughly three degrees apart. The ringed planet shines twice as bright as its distant neighbor. To the west, dimmer than either, is ruddy Mars. Even so, Mars’ steady orange-red hue makes it easy to distinguish from any neighboring stars and their tell-tale twinkle.

Light from Regulus, the 25th brightest star, travels 69 light years before reaching us. By contrast, light from 18th brightest Deneb travels 1,500 light years, and light from third-brightest Alpha Centauri travels a mere 4.3 light years before reaching us.

But even a few light years is a vast distance. Appearing as nothing more than specks of light in the night sky, stars twinkle from color to color as their rays are warped and distorted passing through earth’s atmosphere. No matter how small, however, the naked-eye planets appear as distinct circles of light, only twinkling when ever-so-close to the horizon.


Illustration: © Copyright 1925 M.C. Escher/Cordon Art-Baarn-Holland; Graphics: © Copyright 2007 Pacific Publishers. Reprinted by permission from the Tidelog graphic almanac. Bound copies of the annual Tidelog for Chesapeake Bay are $14.95 ppd. from Pacific Publishers, Box 480, Bolinas, CA 94924. Phone 415-868-2909. Weather affects tides. This information is believed to be reliable but no guarantee of accuracy is made by Bay Weekly or Pacific Publishers. The actual layout of Tidelog differs from that used in Bay Weekly. Tidelog graphics are repositioned to reflect Bay Weekly’s distribution cycle.Tides are based on National Oceanic and Atmospheric Administration and are positioned to coincide with high and low tides of Tidelog.

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