By Kevin Beck Updated Mar 24, 2022
Chasing Light – Photography by James Stone james-stone.com/Moment/GettyImages
There are 88 officially recognized constellations in the night sky, of which 14 represent human figures and 29 depict inanimate objects. These patterns were conceived by the ancient Greeks, who named them after mythological figures and everyday objects.
The sky is divided into celestial hemispheres. Instead of latitude and longitude, astronomers use right ascension and declination. Because the Earth rotates around its axis, the heavens appear to spin around the celestial poles. Consequently, observers in the far north cannot see constellations that lie near the celestial south pole – a fact that helped ancient astronomers determine their own latitude when they first mapped the sky.
Orion is one of the most recognizable constellations, visible from nearly every point on Earth thanks to its declination of approximately +5° – almost on the celestial equator. If you can’t yet picture Orion, an interactive star chart is a great tool to explore its shape and relation to nearby constellations.
Named after the legendary hunter, Orion’s shape resembles a bow tie turned on one end, with two prominent stars marking his upper and lower limbs. In the middle, three bright stars form a tight line – the famous belt that gives the constellation its name.
The belt consists of three stars: Alnitak (ε Orionis), Alnilam (ζ Orionis), and Mintaka (δ Orionis). Alnilam is slightly brighter, but the difference is subtle to the naked eye. Directly below the belt, a fainter line of stars – Orion’s sword – culminates in the Orion Nebula (M42), a rich cluster of young stars visible as a hazy patch to the unaided eye.
In astronomy, a collection of stars that is not a full constellation but stands out as a recognizable pattern is called an asterism. Orion’s belt is a classic asterism, alongside the Big Dipper handle, the Summer Triangle, and the Winter Hexagon.
Because Orion lies near the celestial equator, it is visible year‑round from most mid‑latitude locations. In the United States, central Europe, and parts of mainland China, the best time to view Orion is around 9 p.m. in winter months, when the sky is clear and the constellation is high in the southern sky.
Orion is part of the Winter Hexagon, a loose grouping of seven bright stars spanning six constellations: starting with Rigel, then Sirius (Canis Major), Procyon (Canis Minor), Castor and Pollux (Gemini), Capella (Auriga), and Aldebaran (Taurus).
Betelgeuse (α Orionis) is the brightest star in Orion and the 12th brightest in the night sky. This red supergiant is a variable star, with its brightness waxing and waning over time.
Rigel (β Orionis) is a blue supergiant that outshines Betelgeuse, ranking 7th in overall brightness. It lies on Orion’s lower arm.
Bellatrix marks Orion’s left shoulder and, while only the 22nd brightest star in the sky, it contributes to the constellation’s iconic silhouette.
