Guiding your celestial way on the longest night
The Local · 22 Dec 2010, 09:53
Published: 22 Dec 2010 09:53 GMT+01:00
Do you find the night sky confusing? If so you’re not alone. The heavens initially look like a cluttered jumble of tiny points of light, but with a little practice you can find your way around just as the ancients did.
Fortunately winter nights hold some of the best and the brightest of all the constellations. And with today, December 22nd, being the longest night of the year you’ll have plenty of time to look.
Seasonal skies often have one constellation that serves as a key for helping to find our way around and this month contains one of the best examples; Orion, the Hunter. And unlike many such figures it also resembles the mythological character it’s named after.
Facing southeast your eyes will probably be naturally drawn to a line of three stars of similar brightness that are fairly close together. This is the “belt of Orion” and it sits in the center of an elongated rectangle whose four corners are marked by bright stars, one of which, Betelgeuse, is conspicuously red-colored.
It marks the giant hunter’s right shoulder, which is confirmed in the star’s name as when it’s translated from Arabic means “armpit of the mighty one.” While not very flattering it is in fact functional. Orion’s right arm raised over his head is wielding a large club that he uses while hunting and his left arm is stretched out in front with an old lion skin draped over it as a form of shield. Crossing diagonally down to the right from Betelgeuse and we find bright blue-white Rigel in his left ankle.
Returning to the three belt stars and following them down diagonally to the left you will find dazzling Sirius – the famous “Dog Star” – at the tip of the nose of Canis Major, the Large Dog. This is the brightest star in the nighttime sky, but only because it’s relatively close to us at its distance of 8.6 light years. This means that its light has taken almost nine years to reach us, so as you gaze at it this month that light started its travel earthward in 2002 and this a relatively close star!
Let’s use Orion’s belt again, but this time travel up and to the right where we come across orange-red Aldebaran, the right eye in the v-shaped face of Taurus, the Bull. Known for some 4,500 years, it is one of the oldest constellations. Like Orion, Taurus bears some resemblance to its namesake complete with a pair of very long horns.
A line extending from Orion’s left ankle (Rigel) and out from his right shoulder (Betelgeuse) bring us to our next group; Gemini, the Twins. Its look-a-like stars, Pollux and Castor, were named to honor the twin brothers who sailed on the mythological quest with Jason and the Argonauts. Gemini has the distinction of having two famous modern solar system bodies discovered in it; Uranus in 1781 by William Herschel and Pluto in 1930 by Clyde Tombaugh.
The last and certainly the least of our constellations lies between Gemini, tonight’s Moon and the horizon. Canis Minor, the Little Dog, is one of the smallest constellations, consisting of essentially two bright stars and a smattering of faint ones. You will know that you have found it since its brightest star, Procyon, makes a perfect equilateral triangle (known as the Winter Triangle) with Sirius and Betelgeuse. Procyon is a Greek name meaning “before the dog,” which is appropriate since it rises above the horizon about an hour and 45-minutes before the Dog Star does.
The Moon is shown for December 22nd, but is also faintly marked at the same time for the next three nights so that you can see just how much our natural satellite moves per day.
If you happen to own a pair of binoculars take them out on a clear night and slowly sweep them around the sky. There are easily far more stars than can be seen with the naked eye. Take a look at the Moon; you’ll see thousands of impact craters and large dark patches of what was once molten lava that flowed out from its interior billions of years ago.
Three other objects of optical interest can also be easily found. Below Orion’s belt hangs a faint naked eye “sword.” Looking at the dull spot in its center you can see a grayish-green haze. This is the famous Orion Nebula, a gigantic cloud of gas and dust where stars are known to be in the process of forming.
Astronomers estimate that in the part that’s glowing there is enough material to form about 10,000 stars like our own Sun. Moving on, the v-shaped face of Taurus is actually a cluster of stars, the Hyades, that all formed together out of a nebula similar to that in Orion. Lastly, just above Taurus’ back, is a beautiful cluster of stars that are known as the Pleiades, or Seven Sisters. They too are a cluster like the Hyades, though they lie some three times farther away from us and as a result look smaller and more compact.
When stargazing be sure to dress warmly and bring along a thermos of something hot and nonalcoholic to drink (alcohol can affect your eyes’ dark adaptation). Protect your night vision by using a lit flashlight with a piece of red gel taped over its lens, or by putting your flashlight into a red plastic, or a brown paper, bag. Any of these will help cut down on the flashlight’s brightness while allowing you to see the black and white version of the sky map that you can print out to take with you.
Should it be cloudy on December 22nd you can still use the same map again on a night that’s clear. Each evening the same stars rise a little earlier so that after one week (December 29th) it will look the same as the map at 21.00 while two weeks later (January 6th 2011) at 20.30.
Editor's note: the winter solstice occurred at 12:48am on December 22nd Swedish time, but the longest night of the year in Stockholm will occur from Wednesday to Thursday, December 22nd to 23rd.