Find your way around the night sky! Below is a free sky map for December 2015 as well as a printable version, courtesy of astronomer Jeff DeTray.
Sky Map for December 2015
Each month, Jeff DeTray’s Sky Maps provides a sky map which highlights beautiful events in the evening sky—stars, constellations, planets, conjunctions with the Moon, meteor showers, and other amazing celestial objects. Follow more of Jeff’s sky adventures at AstronomyBoy.com.
Click-and-Print Sky Map
Just click here or on the image below to open the printable map—then bring outside!
Sky Map Highlights: December 2015
Asterisms and Meteors Rule the Sky
It’s human nature to search for patterns; that’s how the constellations of the night sky came to be. The ancients gazed at the heavens and saw kings and queens, heroes and warriors, lions and eagles. Different cultures saw different patterns. It was not until modern times that astronomers agreed to divide the sky into 88 official constellations. By definition, every star belongs to one of the 88 constellations.
Is Every Star in a Constellation?
Yes! Each constellation is defined as an area of the sky with specific boundaries, like a map of the United States divided into states. Every star lies within the boundaries of a constellation, just like every U.S. resident dwells within the boundaries of one of the states. All of the stars within the boundaries of a constellation are part of the constellation even though they are not part of the “stick figure.”
Although the number of constellations is fixed by international agreement at 88, within these 88 official star patterns are many smaller, unofficial patterns known as asterisms. Asterisms are typically made up of the brightest stars in a constellation. There are several notable asterisms in the December sky.
- Looking north, as shown on this month’s Sky Map, the constellation Cassiopeia, the Queen, hangs high in the sky. Cassiopeia contains many stars, but it’s the big “W” asterism that catches the eye (even though it looks more like a big “M” at this time of year). The big “W” includes the five brightest stars in Cassiopeia. It’s a case where the asterism completely dominates the constellation.
- A similar example is the Little Dipper asterism, which sits below Cassiopeia in the constellation Ursa Minor, the Lesser Bear. The stars of the Little Dipper are the brightest in the Ursa Minor constellation.
- The sinuous body of Draco, the Dragon, loops around the bowl of the Little Dipper. Follow the body to the left until you come to the four-sided asterism forming the head of the Dragon. Here the asterism is only a small part of a much larger constellation.
- Above Draco is Cepheus, the King (Cassiopeia is his queen). The main portion of Cepheus is the House asterism, which clearly resembles a child’s drawing of a home, albeit tipped on its side.
- To the left of Cepheus is Cygnus, the Swan. His beak is down and to the left; his tail is the bright star Deneb. But within the body of the Swan are five bright stars forming the Northern Cross asterism, with Deneb at its top. The Northern Cross asterism is often visible even when the larger portion of Cygnus is too dim to see.
- Finally, on the right side of the map, is Auriga, the Charioteer, which contains the lopsided Pentagon asterism.
From a not-very-dark location, you can often spot an asterism even when most of the stars in a constellation are too dim to be seen. And since asterisms are entirely unofficial, you are free to give a name of your own to any distinctive pattern of stars that catches your eye!
Geminid Meteor Shower 2016
While you’re eyeing the sky, don’t miss the annual Geminid meteor shower on the nights of both December 13 and 14. The Geminids are one of the best and most reliable meteor showers of the year. The Moon will be a slim crescent, so it won’t interfere with meteor viewing. As long as the sky is clear and you’re in a dark location, expect to see a shooting star per minute in any part of the sky from darkness to the wee hours. If your schedule or curiosity allows, you might also see some meteors a few nights before and after these dates, too.
DECEMBER 2015 Sky Map
Click here or on image below to enlarge (PDF)
Sky map produced using Chris Marriott’s Skymap Pro
See our Sky Watch page for more highlights of the monthly sky, courtesy of The Old Farmer’s Almanac.