The night sky is so vast; where do you start? Finding your way through the sky begins with a few dominant constellations, containing everything from star clusters and nebulae to obscure galaxies. If you keep looking upward, you’ll see these five constellations parade throughout the sky and through the seasons.
1). Andromeda (The Chained Maiden)
Andromeda, the Chained Maiden constellation, can be seen from August through February. This large constellation in the northern sky is conspicuous thanks to its attachment to the neighboring constellation Pegasus and that constellation’s Great Square asterism. The brightest star, Alpheratz, which represents the head of the maiden, happens to be shared with Pegasus. This blue giant star lies 97 light-years from Earth and shines 200 times brighter than our sun. Four main stars of Andromeda form a curved line toward the east, with Mirach representing her hips and Almach her chained foot. Although Mirach is nearly identical in brightness to Alpheratz, it is a larger red giant 197 light-years away.
Although Andromeda is considered a northern constellation, most of its stars can be glimpsed from the Southern Hemisphere, but always near the horizon, making it a bit trickier to observe its famous deep-sky objects. The most celebrated of these is the grand spiral called the Andromeda galaxy, or Messier 31. This, the closest large galaxy to our Milky Way, lies 2.5 million light- years away. To the surprise of many people, it can be spotted with the naked eye from a typical suburban backyard on a clear autumn night. It represents one of the farthest objects the unaided human eye can see in the universe.
2). Canis Major (The Great Dog)
Canis Major is the larger of the two faithful hunting dog companions to Orion, the Hunter (explained below.) Standing by the Hunter’s foot, the Great Dog is an easy-to-find constellation visible from most areas of the world, thanks to being positioned just south of the celestial equator. Canis Major’s sparkling eye is the brightest star in the sky: Sirius.
The dog days of summer were named specifically for the Dog Star. In the Northern Hemisphere, ancient sky-watchers noticed the intensely bright star would rise and set with the sun. The combined power of the two suns was thought to be the cause of the stretch of hot weather experienced in late summer.
For binoculars and telescopes, Canis Major is rich in star clusters. Leading the pack is the beautiful open cluster M41, also known as the Little Beehive, which lies only four degrees south of Sirius. Containing some 80 stars, this fourth-magnitude cluster is 2,300 light-years away, yet is visible as a hazy patch to the naked eye on a dark night. It is an impressive sight through a backyard telescope, with orange stars scattered within.
3). Orion (The Hunter)
Visible across the world, Orion is one of the most identifiable as well as one of the oldest constellation figures, crossing cultures and thousands of years. Orion straddles the celestial equator, so it is well known to observers in both the Northern and Southern Hemispheres and holds the record for containing the most bright stars in one stellar pattern.
Many stories are attached to Orion, a great hunter in Greco-Roman myths. The most famous says that he was stung by a scorpion (Scorpius) in an epic battle, which is why the two figures have been placed in opposite parts of the sky. Orion boasts two first-magnitude stars, with Betelgeuse marking the shoulder to the viewer’s left and Rigel his foot on the right. Sitting between Rigel and Betelgeuse is Orion’s stellar line of three stars, Alnitak, Alnilam, and Mintaka, marking the Hunter’s belt.
Orion includes an area of the Milky Way that features intense star production. Beneath the Hunter’s belt, in the middle of three stars that form Orion’s sword, is the Orion Nebula (M42). Visible to the naked eye as a fuzzy, faint patch, in backyard telescopes delicate wreathlike structures show where star formation is taking place at a furious pace.
4). Crux (The Southern Cross)
One of the most famous of all southern constellations, Crux is the smallest constellation in the sky, yet it is among the most recognizable. Its distinctive cross asterism is marked simply by four bright stars. In ancient times before Earth’s precession shifted the stars toward the south, the stars of Crux were visible from Europe. But it wasn’t until the 17th century, when European navigators sailing south recognized the cross-like pattern, that Crux became its own official constellation. While best explored from south of the Equator, keen-eyed sky-watchers as far north as the southern tip of Florida can glimpse the Southern Cross.
Crux straddles a rich section of the southern Milky Way band and so is filled with deep-sky treasures of all kinds. Just east of Crux lies what appears to be a hole in the sky—a dark region devoid of stars known as the Coalsack Nebula. It is clearly visible to the naked eye as a strikingly large, dark gas cloud silhouetted against a bright star-studded Milky Way.
5). Ursa Major (The Great Bear)
Ursa Major, also known as the Great Bear, is one of the most prominent northern constellations, and its main claim to fame is that it contains the Big Dipper, a highly recognizable asterism. The easily identifiable Big Dipper represents the bear’s rear torso and tail, with the other stars of the constellation mapping out its long nose and legs. For most observers in the Northern Hemisphere, the Great Bear is close enough to the north celestial pole that it never sets below the horizon, and it rotates around the North Star once a day.
While to the ancient Greeks this stellar group represented a large bear, other cultures saw everything from a chariot to a horse and wagon, a team of oxen, and a hippopotamus (by Egyptians, who had likely never seen a bear). Some Native American tribes believe the cup of the dipper represents a bear and the stars in the handle represent warriors who pursue it.
Finally, remember that you will get your best viewing on moonless nights away from brightly lit areas. Give your eyes time to adjust to the darkness—and good hunting!
National Geographic Stargazer’s Atlas: The Ultimate Guide to the Night Sky provides a detailed tour through the night sky and its wonders, including maps to help guide the exploration. Available wherever books are sold.