Spring officially begins at 10:57 this morning. For the northern hemisphere, this moment in time (and often the day it occurs) is called the spring or vernal equinox.

Because the Earth moves around the sun completely once a year, the sun appears to move slowly across the sky from day to day. When the sun crosses directly over the equator from the southern to the northern part of the sky, winter officially gives way to spring.

“Equinox” means “equal night” — the hours of day and night are supposedly equal. For Tucson’s latitude of approximately 32 degrees north, the times of equal daylight (from sunrise to sunset) and night (from sunset to sunrise) are five to six days prior to March 21 and five to six days after Sept. 21.

To celebrate the start of spring, look for a challenging constellation, Cancer the Crab, which is directly south and 80 degrees (nearly overhead) above the southern horizon at 9 p.m.

Bright Procyon in Canis Minor to the west (right), Pollux in Gemini the Twins to the north, and Regulus in Leo the Lion to the east (left) form a large triangle with Cancer in the very center of the triangle.

Cancer is mainly composed of five stars which form an upside down Y. It is faint but makes up for its unassuming appearance by have a giant star cluster, the Beehive, right in its middle.

The Beehive is also known as M44. The famous French astronomer Charles Messier (1730-1817) included it as the 44th object in his catalog of important sky objects, but it has been known since ancient times. It is visible to the naked eye in dark skies and is a gorgeous sight through binoculars. Give it a try.

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