Arc To Mars-turus

Jupiiter pokes out from between "cloud streets" high in the southern sky around 6:30 p.m. on a recent evening. Photo: Bob King

Amazing how quickly the stars and planets slide by. A few months ago you had to stay up late to get a good look at Jupiter. Now it’s front and center (due south) at dinnertime. Everything celestial moves up from the east, peaks at maximum elevation in the southern sky and then eases down into the west. And it’s all because we live on an unstoppable planet traveling 18.5 miles a second around the sun.

You wouldn’t expect the landscape to remain unchanged while looking out the window of a car traveling at 65 mph. Scenes shift by the minute. It’s the same with Earth. As we gaze out into the night sky, starscapes change over days, week and months as we speed ever onward in our orbit. The Summer Triangle’s replaced by the Great Square of Pegasus, which is replaced by Orion, which is replaced by Leo and on and on it goes. The one difference between a fast car and Earth is that the same starry scenes repeat year after year because we travel in a closed loop around the sun, not a straight line.

With night after night of clear skies, January’s Full Wolf Moon got a lot of lookers in the Duluth region earlier this week. Last night through clouds, I could still see enough of the moon to tell it had changed shape. It’s beyond full now and in waning gibbous phase. Looked like an egg to me. And since the angle between the moon, Earth and sun is narrowing, less and less of the moon is illuminated by sunlight with each passing night. We’ll be watching it wane from gibbous to 3rd quarter and finally morning crescent in the next 10 days. The moon also rises later and later as its orbital motion carries it ever eastward.

A grand arc connect the moon-Regulus pair, Mars, Saturn-Spica and Antares in Scorpius tomorrow morning just before dawn. Created with Stellarium

For those of you up around 6 a.m. tomorrow morning (Jan. 12), take a look across the full breadth of the southern sky. The moon will be in conjunction with and directly below Leo’s brightest star Regulus. Now let your gaze slide eastward and you’ll soon bump into fiery orange Mars. Continuing down and left, you’ll soon arrive at the attractive pair of “eyes” formed by Spica and Saturn and finally ruddy Antares low above the southeastern horizon.

Above this grand arc, high in the south, shines the brilliant orange-hued Arcturus. Mars and Arcturus are a near perfect match in color and brightness at the moment. Do their colors look the same to your eye or are they different? Mars is officially at magnitude 0.0 and Arcturus is listed at -0.04, ever so slightly brighter. Can you see this tiny difference? There’s at least one way they should stand apart from one another. I’ll give you a hint: it has to do with our atmosphere. Go out for a look and let us know what you see.

4 Responses

  1. RC

    I’ve just recently started to notice the colors in stars/planets, specifically the reds of Betelgeuse and Mars, and the blue of Rigel. I’m more of a “night owl” than an “early bird”, so I haven’t had a chance to check out the colors of Antares, or Arcturus yet (but I am looking forward to it!). Are there any other stars with strong color that I should be looking for (now or in the future)?

    1. astrobob

      A good one is Aldebaran in Taurus. Another – though fainter – is Kochab or Beta UMi, the second brightest star in the Little Dipper at the end of the bucket.

  2. RC

    We FINALLY got a clear night here in the Twin Cities, and I was able to take a quick peak at Aldebaran with the naked eye (it was too cold to be outside much longer), but I was able to notice the red/orange of Aldebaran. It’s not quite as colorful as Betelgeuse, but it was still visible. Unfortunately, from my back yard the city lights are a little too bright, and they wash out most of the little dipper. Thanks for the tip!

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