The Clockwork Sky and the Wandering King
Look up with the April 2017 sky map to navigate the stars and constellations in the night sky. On this page is both a color sky map and a black and white printable map to bring outside!
Just click here or on the image below to open the printable map—then bring outside!
The night sky is a giant clockwork calendar. On any night of the year, the sky looks exactly the same as it did one year before. Due to the motion of Earth around the Sun, the stars appear to move a little bit each night until a year later, they have returned to their starting positions. Long-time sky gazers look forward to this wonderful natural cycle and welcome the reappearance of familiar star patterns all year long.
There ARE some exceptions to this precision, however. Take the Moon, for instance. Because it revolves around Earth, it’s on a schedule all her own and does not return to the same spot in the sky on an annual basis. Less obviously, the planets also follow their own timetables.
Ancient cultures were careful observers of the heavens. They noted that most celestial objects— the “fixed” stars—were very well behaved. They never changed position with respect to one another, and they always returned to the same place in the sky every 365 days. These observers of antiquity also noted that a few strange “stars” seemed to wander through the sky, refusing to obey the rules. These came to be known as “planets,” from the Greek word planetai, meaning “wanderers.” Their names are Mercury, Venus, Mars, Jupiter, and Saturn—the five planets visible to the unaided eye.
On April’s Sky Map, we have splendid examples of both fixed stars and a wanderer.
April Sky Map
Click here or on image below to enlarge this map (PDF).
Sky map produced using Chris Marriott’s Skymap Pro
In the evening at this time of year, the southeast sky is dominated by the Spring Triangle. The bright stars Regulus, Arcturus, and Spica mark the vertices of the Triangle. Year after year, century after century, these three fixed stars have appeared in this exact location and arrangement every spring.
What’s different this year is the presence of one of those pesky wanderers. In this case the interloper is Jupiter, the King of Planets and thus the King of the Wanderers. Jupiter wandered into the Spring Triangle last year, and over the next few months, he will slowly wander into a different part of the sky. A year from now the Spring Triangle will return as it always does, but the Wandering King will be elsewhere.
To the right of the Spring Triangle slithers Hydra the Water Snake, the largest of all constellations. The snake’s head is to the upper right of Regulus, while its tail ends well below Spica. Hydra is fairly dim, but the view gets better as the night wears on. Stay up past midnight for a clearer view as Hydra rises higher in the sky.
Nestled in a coil of the Water Snake’s body are the constellations Crater the Cup and Corvus the Raven (or Crow). Crater is comprised entirely of dim stars, so you’ll need a dark location to see it well. In contrast, the main stars of Corvus are all comparatively bright, so you should find it fairly easy to locate the bird’s four-sided figure. Both of these constellations were included on a list created by the Greek astronomer Ptolemy in the 2nd century. Even then the stars comprising these two constellations returned to the same location each year—like clockwork.
Enjoy astronomy? Check out Bob Berman’s column, “This Week’s Amazing Sky.”