Stars over Sisters

Last month, this column referred to three bright stars that form a large equilateral triangle called the Winter Triangle. But this part of the sky also yields an even larger geometric shape. In March, look to the southwest to see a somewhat irregular-shaped hexagon.

The hexagon consists of six prominent stars located in six different constellations. It is easy to pick out because it includes the recognizable constellation of Orion. Starting near Orion's foot is the blue-colored star Rigel. Moving in a clockwise direction from here we encounter Sirius, the next, and brightest, member of the six-sided shape. It resides in the constellation of Canis Major. Procyon, in the constellation of Canis Minor, is next as we continue our clockwise sweep.

Proceeding on our swing northward, we enter the constellation of Gemini and find Pollux, the dimmest member of the hexagon. Next is the bright yellowish star Capella, located in the constellation of Auriga. The sixth and final member of our celestial hexagon is Aldebaran, an orange-colored star in the constellation of Taurus; then back to Rigel to complete the circuit. You'll notice a bright reddish star within the hexagon. This is Betelgeuse and it marks Orion's eastern-most shoulder.

Spring begins in the northern hemisphere at 10:14 p.m. PDT on March 19, when the sun will be directly overhead at the earth's equator. When the sun makes this equator crossing in traveling from southerly to more northerly latitudes, it is called the vernal equinox. At this time, the length of day and night are nearly equal ("equinox" means equal night.)

The brightest planets in the solar system are lining up in the evening sky this month. Venus and Jupiter are in the west and stand out of the twilight even before the sky is completely dark. The two planets are converging, and by mid-March they will lie only three degrees apart. At that time you'll be able to hide them both behind a pair of outstretched fingertips.

Mars is the third member of March's parade of planets. On March 3, the Red Planet, Earth and the sun will be in alignment. This condition is called opposition and occurs when a planet and the sun are on opposite sides of the sky as referenced from the earth. Two days later the two planets will make their closest approach, a distance slightly less than 63 million miles. Mars is only about half the size of the Earth.

The month opens with a waxing moon that becomes full on March 8. After this date the moon begins to wane, fading to third quarter on March 14. The moon is new on March 22, and then brightens again, reaching first quarter on March 30.