Set your eyes SE at 21:00 local time for our last installment of the Winter sky. As of today, the near-full moon is in Cancer blotting out many of the dimmer stars. You may want to wait until the 15th of January when the moon is below the horizon to see some of what I’m writing about today. Locate our red friend Betelgeuse (alpha Ori) as your starting point. From there, tonight’s journey will take us to the charioteer, the twins, and the unicorn.
Need a ride?
From Betelgeuse, look north (up) and east (left). The 0.05 magnitude star you’ll run into is Capella (alpha Aur). The constellation Auriga is derived from the Latin word for “charioteer” or, in modern terms, “chauffeur.” Auriga’s ring of stars is supposed to represent the charioteer’s helmet.
Capella is a quadruple stars system about 42 light-years from earth. The two primary stars are type G giants and are accompanied by two red dwarfs. For sci-fi and Star Trek fans, Capella is the fictional setting for “Friday’s Child,” a season-two episode of the original Star Trek series which first aired 1 Dec 1967.
Just down and to the left of Capella, you’ll run into Menkalinan (Beta Aur. Menkalinan is a 1.90 magnitude trinary system with two white sub-giants and a red dwarf all about 85 light-years from earth.
Gemini a naked-eye dream
Let’s return to Betelgeuse base and draw a mental line due east (left). The first bright start we encounter is Alhena (gamma Gem). Continue along your mental straight line to find Pollux. Pollux (beta Gem) breaks the tradition of designating the brightest star in a constellation “alpha” since it’s brother Castor (alpha Gem) bears that distinction. Castor is the bright star right above Pollux. These two stars are the traditional twins, but astronomically-speaking, they have little in common. Castor is a 6-star system made up of blue A-type stars and red dwarfs. Pollux is a single, yellow-orange K-type giant. Pollux’s has a radius almost nine times that of our sun’s. It also has a planet, designated Pollux-b with a mass about 2.3 times that of Jupiter’s, orbiting every 590 days. Pollux-b was discovered in June 2006 so don’t say there is nothing new in astronomy.
The stars of Gemini range about 30 light-years to 1100 light-years from earth. With twelve stars brighter than 4 magnitude, Gemini is a naked-eye dream. It is the exact opposite of our next destination.
Dim, lonely Monoceros’ secrets
Monoceros, the unicorn, lies south of Gemini between the dogs. From Betelgeuse, trace a triangle down to Sirius and left to Procyon. The seemingly empty space of that region is the constellation Monoceros. The unicorn is outlined by stars not much brighter than a 4 magnitude which makes it difficult to see with the moon nearby or from any lighted population centers. Monoceros is indeed one of the least favorite naked-eye destination. Even with a good telescope it doesn’t give up its secrets easily. But the wonders are there.
Beta Monoceros, a 4.60 magnitude neighbor eclipsed by its proximity to Sirius, is a beautiful trinary system which appears fixed from earth. It consists of three B type stars nearly 700 light-years away. In 1781, William Herschel took the first close look at Beta Mon and declared it “one of the most beautiful sights in the heaven.”
Alpha Monoceros is located about halfway between Sirius and Procyon (and slightly south). It is a G type star not very different from our own sun. If you can see it, you’re getting a good idea how our own sun looks from 144 light-years away, small, dim, and unassuming. I wonder if someone on a planet around Alpha Monoceros is starring back.
There is one last, non-naked-eye object in the unicorn. At magnitude 15.74, V838 is invisible to all but the best telescopes. About 20,000 light-years from earth, V838 went unnoticed until 2002 when it underwent a violent outburst. Originally thought to be going nova, astronomers have since put forth several non-nova theories about its sudden activity. One theory involves a star on its last leg. Another theory speculates that two stars are colliding. Regardless of which is right, the Hubble telescope image of the star is a thing of beauty.
This concludes our tour of the winter sky, my favorite part of the night sky. Hopefully, I’ll return to the old blog with something new from Associated Content this week. Until then, take something hot to drink when you go out under the wonderful winter sky.