Tuesday will mark the winter solstice
'Tis the time of year for making merry, and also for changing seasons.
That's what we'll do this Tuesday morning at 10:58 a.m., the moment of the winter solstice, the first day of winter, and also the moment we start gaining daylight once again!
You've undoubtedly noticed that the sun takes a very low arc across the southern sky this time of year, rising in the southeast and setting in the southwest, spending less than nine hours above the horizon.
On Tuesday,the sun reaches its lowest point in the southern sky. This low sun angle means that we're not getting nearly the amount of solar power and radiation as we get in the summer.
From now through late next June, the sun's arc across the heavens will get higher and higher, and we'll eventually get warmer. However, the coldest weather of the winter is yet to come. That's an injustice!Blame it on the north polar regions. There's been little or no sun up there for some time now, and super cold air has really built up. The cold has to go somewhere, and the general circulation of global winds causes that frigid air to spill our way in intervals until early March. I call it the polar hangover effect.The sun's daily path in the sky reflects the daily and annual motions of the Earth. When you were young, you learned that Earth's rotation causes the sun to rise in the east and set in the west. The Earth's orbit around the sun also affects how we see our home star in the sky, mainly because the Earth's axis is tilted to its orbit around the sun by a 23.5-degree angle.Tuesday, on the day of the winter solstice, the Earth's northern hemisphere — where we live — is tilted at the maximum angle away from the sun's most direct rays. The noontime sun is shining directly over the latitude line called the Tropic of Capricorn, 23.5 degrees in latitude south of the Earth's equator. Does that 23.5 degrees sound familiar? It should.In our Butler sky the sun's noon-time angle will be as far south as it can be in our sky at 25.5 degrees above the horizon.Six months later, on June 21, the day of the summer solstice, we'll be on the other side of Earth's orbit around the sun and the northern hemisphere will be basking in the sun's most direct rays. That will be reflected in our sky as the sun takes a long, high arc from the northeast to the northwest horizon. On the summer solstice, the noontime sun is at its farthest northern point in our sky. That puts it at a high 72.5 degrees above the southern horizon at noon.After the summer solstice, everything goes in reverse; the sun's path in the sky gets lower and lower and the days get shorter and shorter.During this week of Christmas in the early evening sky you won't see three traveling wise men, but you'll easily see three traveling bright planets. Toward the end of evening twilight. Look for the three brightest “stars” you can see in the southwestern sky.In reality, those stars are Jupiter, Saturn and Venus, lined up neatly in a diagonal row. The very brightest is Venus, not far from the horizon. You can't miss it! The next brightest is Jupiter, much higher in the southwestern sky. Between Jupiter and Venus is Saturn.You need to look for this planetary trio as soon as you can after sunset because one by one they'll be slipping below the horizon.Our fellow planets, traveling around the sun, are putting on quite a show. Venus will resemble a crescent moon with a small telescope or binoculars. Because the orbit of Venus around the sun lies with Earth's orbit Venus goes through phases just like our moon.Set your optics on Jupiter and you'll see the bright disk of the giant planet along with up to four tiny stars lined up on either side of it. These are Jupiter's four brightest moons that constantly change positions from night to night as they orbit their gravitational master.With a small telescope you can still make out the ring system on Saturn but it will probably appear a little fuzzy. That's because it's close to the blurring effects of Earth's atmosphere near the horizon.Saturn also is nearing its farthest distance from Earth, and this week it's nearly a billion miles away!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.
