Among the many constellations that adorn the night sky, the circumpolar constellations hold a special place. These constellations are visible year-round from certain latitudes and have been used by various cultures for navigation, storytelling, and religious purposes. Astronomers and stargazers also use them to identify other stars and constellations in the sky. In this article, we’ll explore the circumpolar constellations.
What is a circumpolar constellation?
Circumpolar constellations are the constellations that are always above the horizon when observed from a particular location on the Earth. They can be seen in the sky every night throughout the year, as opposed to seasonal constellations, which are only visible during certain seasons.
How do circumpolar constellations work?
All the constellations appear to circle around the celestial poles. The northern constellations rotate around Polaris, or the North Star, the closest star to the North celestial pole nowadays. The southern constellations rotate the South celestial pole, which is not marked by any bright star.
At the Earth’s North/South Pole, the corresponding celestial pole is directly overhead, and the entire Northern/Southern Sky is always above the horizon. But as you travel towards the equator, the celestial poles move closer to the horizon, and some constellations begin to rise and set at some part of their daily motion, while others always stay in the sky.
How many circumpolar constellations are there?
The exact number of constellations you see as circumpolar depends on your geographical location. For example, if you are at a latitude of 30ºN, all the constellations within a 30-degree radius from Polaris will always be above the horizon for you. Closer to the equator (from about 25ºN to 15ºS), all the stars rise and set at some time, so there are no circumpolar constellations for these latitudes. Try an experiment with Sky Tonight: scroll through the Time Machine (panel at the upper part of the main screen) and see what constellations never dip below the horizon in your location.
The constellations that are always visible from northern latitudes (above 60ºN) include:
- Ursa Major;
- Ursa Minor;
The brightest constellations that are always visible from southern latitudes (below 60ºS) include:
- Triangulum Australe.
The following constellations are also circumpolar from southern latitudes but are not so prominent and easy to see: Octans, Apus, Pavo, Indus, Tucana, Hydrus, Mensa, Volans, Dorado, Reticulum, Chamaeleon, Circinus, Musca, Horologium, Corona Australis, Telescopium, Norma, and Ara.
When can you see circumpolar constellations?
Circumpolar constellations can be seen year-round from the locations north or south of the equator. However, they slightly change their position in the sky throughout the year, meaning that in some seasons, they climb the highest in the night sky, and the sky objects within their borders are best seen. Use the Star Walk 2 and Sky Tonight stargazing apps to find these constellations anytime.
Northern circumpolar constellations
Let’s take a look at the brightest circumpolar constellations seen from mid-northern latitudes. They feature bright stars and prominent asterisms that can be used for navigation and locating objects in the sky.
Ursa Major is one of the largest and most recognizable constellations in the sky. It can be easily identified by the Big Dipper asterism, which is one of the most prominent star patterns of the night sky. The constellation also hosts numerous well-known deep-sky objects. Through binoculars, you can observe the Bode’s Galaxy (M81) and the Cigar Galaxy (M82). Meanwhile, the Owl Nebula (M97) and the Pinwheel Galaxy (M101) can be viewed using a telescope. Ursa Major is observable from above 30ºS and is circumpolar from above 50ºN.
Ursa Minor is harder to find than Ursa Major. If you are using Star Walk 2 and Sky Tonight, you can just type the name of the constellation into the search field and follow the app’s directions to find it in the sky above you (check our video tutorials on Star Walk 2 and Sky Tonight to see how easy it is). Also, you can locate the Big Dipper first, and then follow the pointer stars to find Polaris — the brightest star in Ursa Minor, which also marks the North celestial pole. Deep-sky observers can find the Ursa Minor Dwarf galaxy (PGC 54074, UGC 9749) within the constellation’s borders. Ursa Minor is visible from above 10ºS and is circumpolar from above 20ºN.
In the article about the constellations of the Northern Hemisphere, we’ve already covered the constellation Cassiopeia, known for its W-shaped asterism. The most prominent star in the constellation is Schedar. The notable deep-sky objects within the constellation include star clusters (M52, M103, NGC 457, NGC 663), several galaxies (NGC 147, NGC 185, NGC 278), and the Pacman Nebula (NGC 281) — a cloud of space gas named after the character of the eponymous game. Cassiopeia is visible from above 20ºS and is circumpolar from above 45ºN.
Next to Cassiopeia, you can find the constellation Cepheus, which resembles a stick figure of a house. Along with Errai (the future North Star) and Alderamin (the brightest star in Cepheus), one of the notable stars here is Herschel’s Garnet Star — one of the largest known stars. This red supergiant is easy to see with the naked eye. Below the Garnet Star, you can find the Elephant’s Trunk Nebula (IC 1396) with the help of a telescope. Not far from Alderamin, lies the Iris Nebula (NGC 7023). The star clusters NGC 188, NGC 7129, NGC 7235, and NGC 7261 also make good deep-sky targets. Cepheus can be seen from above 10ºS and is circumpolar from above 35ºN.
Draco is the 8th largest constellation of the Northern Sky. It is notable for containing the star Thuban, which was the North Star around 4,000 years ago during the time of the ancient Egyptians. The constellation also contains several other notable stars, including Eltanin and Rastaban. Along with Thuban, they are the three stars above magnitude 3 in the constellation. Draco is also home to the Cat’s Eye Nebula (NGC 6543), Spindle Galaxy (M102), Draco Dwarf Galaxy (PGC 60095), Tadpole Galaxy (PGC 57129), and many other deep-sky objects. Draco is observable from above 10ºS and is circumpolar from above 40ºN.
As you may have noticed, many deep-space objects have interesting names. Take our quiz and see if you can guess the name of the nebula by the way it looks!
Southern circumpolar constellations
There are nearly two dozen constellations that are always visible from mid-southern latitudes. Among them, we’ve selected the most prominent and easy-to-find ones, featuring bright stars and standout asterisms.
Carina is one of the largest constellations. It contains the second-brightest star in the night sky, Canopus, as well as two cross-shaped asterisms — the False Cross and the Diamond Cross, which are often confused with the constellation Crux, or the Southern Cross. Also, Carina is a home for a number of notable deep-sky targets: the Carina Nebula (NGC 3372), Wishing Well Cluster (NGC 3532), NGC 3603, and NGC 2808. The constellation can be seen from below 20ºN and is circumpolar from 35ºS.
Crux, also known as the Southern Cross, is one of the most recognizable constellations in the Southern Hemisphere. It consists of four bright stars that form a cross shape and has been often used for navigation. It also contains the bright Jewel Box (NGC 4755) star cluster, which is visible even with the naked eye. Crux can be seen from below 20ºN and is circumpolar from below 33ºS.
Centaurus is home to Alpha Centauri — the closest star system to our own and one of the brightest stars in the night sky. Along with Hadar (the second-brightest star in the constellation), it forms a line that points at Crux. Also, Centaurus contains Omega Centauri (NGC 5139), the Blue Planetary Nebula (NGC 3918), and Centaurus A, NGC 4603, NGC 4622, and NGC 4945 galaxies. The constellation is observable from below 25ºN and is circumpolar from below 60ºS.
We have also discussed Carina, Crux, and Centaurus in our article about the constellations of the Southern Hemisphere.
Triangulum Australe is a small constellation that is circumpolar from most of the Southern Hemisphere. It has the shape of an equilateral triangle and can be easily identified in the sky. The constellation features the bright star Atria, and a few deep-sky objects — the open cluster NGC 6025, planetary nebula NGC 5979, and spiral galaxy NGC 5938. Triangulum Australe is visible from below 25ºN and is circumpolar from below 30ºS.
Circumpolar constellations: a brief summary
Circumpolar constellations are visible in the night sky throughout the year and never set below the horizon as seen from particular latitudes. These constellations are important for navigation and astronomy as they can be used as reference points for determining direction. The northern circumpolar constellations include Ursa Major, Ursa Minor, Cassiopeia, Cepheus, and Draco. The southern circumpolar constellations include Carina, Centaurus, Crux, and Triangulum Australe.