All around us, there have already been signs of spring. Due to a change in the law several years back, daylight savings time has kicked in earlier. If you're a frequent reader of Skywatch, you know that I'm not a big fan of that change. It means I have to wait until later in the evening to start my star watching because of the later sunset. I'm retired now, but I had to wake up at 3:30 am when I was working, which didn't leave much time for sleeping!

Spring officially begins this Sunday, March 20, at 11:33 a.m. EDT. The beginning of spring is also known as the vernal equinox, and that's when the sun starts to rise and set above an imaginary line in the sky called the celestial equator, a projection in the sky of Earth's terrestrial equator. Until June 21, the sun will arc higher and higher in the sky.

One fallacy about the vernal equinox is that day and night are equally long at 12 hours each. That's not true because of something called astronomical refraction. The shell of the atmosphere surrounding our Earth bends the light coming from the sun, or any other celestial object for that matter. The maximum effect of the bending of light is along the horizon where, from the observer's perspective, the atmosphere is the thickest. Believe it or not, when the sun appears to be right on the horizon, it's actually below the horizon. So when you see the sun setting, it's already been below the horizon for about five minutes. Conversely, in the morning, the sun may appear to be just above the horizon when it's actually still below the horizon. I know that sounds crazy, but that's what happens! If you check the sunrise and sunset times for this Thursday, you'll discover that on that day, the days are already about ten minutes longer than the nights.

So when do days become equal to nights this time of year? The answer is St. Patrick's Day! Yet another reason to celebrate one of the greatest feast days of the year.

In the night sky this time of year, one of my favorite signs is the appearance of the bright star Arcturus, the second-brightest nighttime star. When you start to see it rising in the northeast around 9:30 pm, you know that spring is right around the corner.

Another celestial sign of spring is the Beehive star cluster, located in the very faint constellation Cancer the Crab. You shouldn't bother trying to find Cancer, though, because it's one of the faintest constellations in our sky.

The Beehive cluster is actually brighter than most of the stars in the constellation. Instead, look in the high southeastern sky about halfway between the brighter constellations Leo the Lion and Gemini the Twins.

If it's dark enough where you are, the Beehive cluster, known astronomically as Messier object or M-44, looks like a faint patchy cloud. When the ancient Greek astronomer Hipparchus observed it around 130 BC, he registered it as a "cloudy star" in his star catalog. The Romans saw it as a manger and called it Praesepe, Latin for manger.

In the early 1600s, when Galileo poked his telescope toward Praesepe and saw it as a cluster of stars, it got the name Beehive cluster. With a small telescope or even a decent pair of binoculars, you can easily see how it got that moniker.

Astronomically the Beehive is considered an open star cluster, a group of young stars that emerged out of the same hydrogen gas nebula. Astronomers believe the stars in this cluster are about 600 million years old. While that's considered a young age for an average star, it is rather old for a cluster of young stars. Many clusters like this are gravitationally broken up before the stars are that old. The Beehive is hanging in there, though. That "teenage mob" of at least 200 stars is over 3,400 trillion miles away and nearly 60 trillion miles wide.

Get ready for spring! But remember, the possible snowfall season continues into late May and early June in Minnesota!

———

Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of "Stars: a Month by Month Tour of the Constellations," published by Adventure Publications and available at bookstores and adventurepublications.net. Contact him at mikewlynch@comcast.net.

Diagram for locating the Beehive Cluster

My Photo of the M44, The Beehive Cluster