The Free Press, Mankato, MN

March 1, 2011

March a good time to spot planets

By Shane Frederick
Free Press Staff Writer

— March is named for Mars but this March Mars is hiding in the daytime sky. It is located close to the sun but don't try to spot it. Early in March bright Jupiter is setting in the west about two hours after sunset. While Jupiter is still visible in the evening it can help you identify the planet Mercury.

As the month progresses Mercury is moving closer to Jupiter low on the western horizon. From March 14-16 Mercury will be visible as a bright star

about 2 degrees or about four apparent moon diameters to the right (north) of a very bright Jupiter. Start watching at about 7:20 p.m. CDT. Be one of the few who has seen Mercury.

By the end of March Jupiter will be lost in the evening twilight. Saturn rises in the east about 8:30 p.m. CST at the beginning of March. Venus is still

a brilliant morning star low in the east before sunrise.

Again it is time for our annual experiment in time travel also known as daylight saving time. Set your clocks forward at 2 a.m. Sunday morning March 13.

Daylight saving time can cause confusion for a few days when some clocks don't get changed. But in 1965 there was a bit more than the usual confusion when St. Paul decided to change to daylight saving time on May 7 and Minneapolis changed on May 23. The very next year congress passed the uniform time act establishing the same time in the nations time zones.

If the full moon in March looks bigger than usual it won't be your

imagination. The full moon occurs 1 p.m. CDT March 19. The moon reaches is closest approach to the Earth one hour later so March's full moon will be the largest of the year. Of course the actual diameter of the moon doesn't change. It is the angular size of the moon, the size it appears in the sky, that changes. The moon's angular size varies from about 0.50 to 0.57 degree.

The sun's apparent size also varies due to the variation in the Earth's distance from the sun but no one notices because understandably, no one carefully inspects the sun. Never look directly at the sun with your eyes or with any optical instrument!

The March equinox, the spring equinox in the Northern Hemisphere,

happens March 20 at 6:21 p.m. CDT. At the equinox the sun rises due east and sets due west. As a result the day and night length are nearly equal. Equal night is the meaning of equinox.

The last half of March is a good time to view zodiacal light. Zodiacal light is sunlight reflected from dust particles that accumulate in the orbital plane of the planets. To see this glow in the sky you first need to find a dark location. Watch the western point on the horizon starting at about half an hour after sunset. With luck you will see a glowing triangle of light with its base on the horizon. The darker your location the more likely you are to

see zodiacal light.

Send comments and questions to Steve Kipp, at steven.kipp@mnsu.edu