Volume XVII, Issue 27 # July 2 - July 8, 2009

Sky Watch

by J. Alex Knoll

Great Antares

Thank heaven this red giant isn’t our sun

The waxing gibbous moon travels along the ecliptic in a shallow arc through southern skies, the same path that the sun will travel during the day six months hence. Look for Luna just a few degrees to the west of Antares, the heart of the scorpion, Friday night.

Antares is the 15th brightest star in our sky second only to Betelgeuse in size. At 520 light years from us, it is the star’s massive girth rather than its temperature, cooler than our sun, that makes it appear so bright. More than 500 times the size of our sun, Antares would stretch past Mars and into the asteroid belt were it the center of our solar system.

Tuesday marks July’s full moon, dubbed the Red Cherries Moon, the Mead Moon, and, with their growth of new antlers, the Buck Moon.

The sun sets around 8:30 this week, revealing Saturn high in the west between the constellations Leo and Virgo. While Saturn is as bright as any star, it is rather disappointing viewed in a telescope, as its rings face us near dead-on.

As Saturn sets around midnight in the west, Jupiter rises in the east. In a dim part of the heavens nestled between Capricornus and Aquarius, there’s no mistaking Jupiter.

For several hours, Jupiter’s rule is unchallenged. Then, a little after 3am, Venus rises in the east-northeast to become the brightest light overhead other than the sun and moon. Almost indistinguishable from the stellar backdrop, ruddy Mars shines just a few degrees west of Venus.

With the approach of dawn, after 5:45 this week, Mercury crests the horizon just before the coming sun. You’ll likely need binoculars and a clear horizon to spot this surprisingly bright planet amid the pre-dawn glow far behind Venus and Mars.

Illustration: © Copyright 1925 M.C. Escher/Cordon Art-Baarn-Holland; Graphics: © Copyright 2009 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.