What's in the sky

Of course, longer days mean shorter nights during which to see the stars. You'll have to stay up a bit later, but the warmer temperatures make it worthwhile.

As May begins, we find the bright planet Saturn and the first quarter Moon located near each other in the southwestern sky. On May 1, the Moon will be to the right of Saturn. By May 3, you'll note that the Moon lies right under Saturn. By May 5, the bright Moon will be far to the left of Saturn, close to the bright star Spica. This is a good time to see how the moon moves across our sky from night to night. Check out the accompanying diagram.

By May 9, the moon will have moved across the entire sky, and will rise at sunset as our May Full Moon. New Moon will be on May 24.

On May 30, the moon, Saturn, and the bright star Regulus (in the constellation Leo) will lie close together.

You'll not see Venus in the May evening sky, but you may catch the bright "morning star" just before sunrise in the east. Jupiter joins Venus in the morning sky. Our largest planet is growing brighter, and will be the other really noticeable "star" before sunrise. Look for Jupiter near the moon on the morning of May 17. On May 21, the moon will be very close to Venus.

The bright constellations of winter continue to disappear in the west during the month of May. Gemini, with its twin stars Castor and Pollux, lie low in the west during early May evenings. By the end of the month, they'll be almost on the horizon by the time the sky darkens.

In the east, look for Cygnus, the Swan (also called the Northern Cross) rising in late evening. Cygnus lies in the summer band of the Milky Way, and will be overhead on summer nights to come. Look for the bright star Vega, located in the dim constellation Lyra, just above the Northern Cross.

Vega is the fifth brightest star in the sky, other than the Sun. 12,000 years ago, Vega was located near the celestial North Pole, and was the "north star" of that time. In another few thousand years, it will do the same again. Why?

As the Earth rotates, it wobbles on its axis, somewhat like a spinning top wobbles as it slows, a movement called precession. One "cycle" of precession takes about 25,800 years -- so in another 25,000 years or so, Polaris will be back as our north star.

The Big Dipper (in the constellation Ursa Major) lies overhead during May evenings. Check out the middle star in the Dipper's handle for a test of your eyesight. There are two stars there if you look close. The brighter star is called Mizar, the dimmer star is Alcor. With a telescope, you can see that Mizar itself is made up of two stars, a double star system.