THE SOUTHWORTH PLANETARIUM
207-780-4249 www.usm.maine.edu/planet
70 Falmouth Street Portland, Maine 04103
43.6667° N 70.2667° W
Altitude: 10 feet below sea level
Founded January 1970
Julian Date: 2458863.16
Julian Date: 2458863.16
2019-2020: LXXXIV
"Such as are your habitual thoughts, such also will be the character of your mind; for the soul is dyed by the thoughts." -Marcus Aurelius
THE DAILY ASTRONOMER
Tuesday, January 14, 2020
Winter Triangle Rising
Unless you've been cloistered in a stardome for the last few weeks enshrouded in eiderdown comforters and surrounded by space heaters while obstainely refusing to interact with other humans, you will know that winter has arrived in earnest. Alternating layers of ice and snow coat our iron-hard Earth and a deep chill settles onto the world during each interminable night. Oh, blah! What a miserable attitude!
Hey, despite the hiemal gloom and widespread dormancy of flora and fauna, the sky remains a veritable festival of brilliant stars. In many ways, the winter sky is the most wonderful of them all: not only is the boundless sky ablaze with beguiling lights, the sun still sets early enough to afford everyone a view onto the cosmos the Sun cleverly obscures every day. Also, the reduced radiational cooling in early evening reduces the atmospheric obscuration: the air is calmer and the view less obscured by the thermal turbulence that ripples through the unquiet summer night sky. Moreover, there is the Winter Triangle. Formed by Sirius (the brightest star), Betelgeuse and Procyon, this triangle is smaller than its Summer counterpart, but brighter. It is the easier of the two patterns to observe.
Now that thee Summer Triangle has largely vanished into the dusk, the Winter Triangle is ascending into the eastern evening sky. January is the famous (well, somewhat well known) Triangle transition month, marking real winter's onset. Today, we welcome the Winter Triangle's return to prominence.
The three stars are each part of a different constellation. Sirius represents the collar of Canis Major, the larger of Orion's two hunting dogs. Procyon is the brighter of the two stars the form Canis Minor, the smaller dog. Betelgeuse is Orion's eastern shoulder star, or in cultures frightened by (and therefore obsessed with) nakedness, Betelgeuse is the clasp on Orion's tunic.
Mythologically, the formidable hunter Orion maintains a stubborn pursuit of the elusive Seven Sisters, or Pleiades. His dogs dutifully follow, despite their greater distance from and, let's face it, far reduced carnal interest in, Atlas' seven daughters. Of course, the constellation stories vary considerably, as we can see in the image above that depicts Orion as facing the other direction.
Astronomically, the stars comprising the Winter Triangle seem quite close together. They are nothing of the sort. Sirius is merely 8.4 light years away, almost at an arm's length. Procyon is slightly farther away at a distance of 11.5 light years. Betelgeuse occupies a far deeper part of the pool at a distance of 620 light years. Whereas we're seeing Sirius as it was in the summer of 2011, and Procyon in the summer of 2008, we're seeing Betelgeuse as it appeared in the early 15th century!
Despite its name, Winter Triangle will remain in our evening sky until May, when it will begin the night low in the western sky. Sirius, being the southernmost star, will vanish first by early May, followed by Betelgeuse in mid May and Procyon by the end of May. Naturally, they will all return to the early morning sky by early September: a cycle that has continued for centuries and will persist for centuries more.
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