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Slain Draco stretched out at Hercules' feet

Tonight around 10 o'clock, face north and look over halfway up into the sky. On your left, in the west, will be the Big Dipper _ cup down and handle up. On your right, in the east, will be the three bright members of the summer triangle _ Vega toward the south, Deneb in the north, and Altair off to the east.

Between these two star groups near the zenith (the overhead point) is a dim meandering chain of stars known as Draco the Dragon. As darkness settles upon the land, Draco's tail flicks over the cup of the Dipper, his back is humped over the Pole Star, and his head is poised beneath the feet of Hercules.

The squarish head, lying northwest of Vega, is the most obvious asterism in this constellation because it is composed of four fairly bright stars, the brightest being Eltanin, the easternmost of the square.

The remaining 13 stars in Draco's body can be traced from northeast of the square head, back toward the southwest, west, then north again.

The stars are fairly bright and the pattern easy to follow.

According to ancient myth, Draco represents the monster that guarded the golden apples in the Garden of Hesperides, located somewhere at the western end of the Earth.

Hercules' final labor (of the famous 12 labors of Hercules) was to fetch some of these golden apples.

Hercules had a desperate encounter with Draco but finally succeeded in slaying the creature and carrying away the precious fruit.

Forty-eight hundred years ago (2800 B.C.) Earth's axis pointed at the star Thuban, third from the end in the tail of Draco, making it the Pole Star at that time.

Earth's axis wobbles like a top, and over a 25,000-year period, it moves at an agonizingly slow pace, eventually describing a vast circle among the stars. This motion, called precession, results from the gravitational attraction of the sun and moon on Earth's equatorial bulge.

Thuban was the North Star at a time that closely coincides with the age of the pyramid builders in Egypt. It has been theorized, in fact, that the descending passage in the Great Pyramid of Khufu at Giza was constructed to point directly at Thuban.

Jeff Kanipe is the editor of Star Date, an astronomy magazine published by McDonald Observatory at the University of Texas at Austin.

STAR DATE

PLANETS

Mercury is at its most visible for the summer this week. Look for an orange-hued "star" in Gemini low in the west-northwest half an hour or so after sunset.

Venus is higher in the eastern morning sky at dawn.

Mars, in Leo, is the red "star" in the southwest at sunset. It sets around 11 p.m.

Jupiter, in Virgo, is in the southwest at sunset. It sets around 2 a.m.

Saturn rises in the late evening and is low in the south by dawn.

EVENTS

Wednesday: Venus is just south of the waning crescent moon in the morning sky.

Thursday: Mercury is at its greatest angular extent from the sun in the evening sky.

Saturday: New moon.

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