Orion, sometimes subtitled The Hunter, is a prominent constellation located on the celestial equator and visible throughout the world. It is one of the most conspicuous, and most recognizable constellations in the night sky. Its name refers to Orion, a hunter in Greek mythology. Its brightest stars are Beta (Rigel) and Alpha (Betelgeuse), a blue-white and red supergiant respectively. Many other of the brightest stars in the constellation are hot blue supergiant stars.
Orion can be easily seen in the night sky from November to February of each year – late fall to winter in the Northern Hemisphere, late spring to summer in the Southern Hemisphere. In the tropics (less than about 8° from the equator) the constellation transits at the zenith.
In the period May–July (summer in the Northern Hemisphere, winter in the Southern Hemisphere) Orion is in the daytime sky and thus not visible at most latitudes. However for much of Antarctica in the Southern Hemisphere’s winter months, the Sun is below the horizon even at midday. Stars (and thus Orion) are then visible at twilight for a few hours around local noon, low in the North. At the same time of day at the South Pole itself (Amundsen–Scott South Pole Station), Rigel is only 8° above the horizon and the Belt sweeps just along it. In the Southern Hemisphere’s summer months, when Orion is normally visible in the night sky, the constellation is actually not visible in Antarctica because the sun does not set at that time of year south of the Antarctic Circle.
Looking for Orion’s Belt in the night sky is the easiest way to locate the constellation Orion in the sky. The stars are more or less evenly spaced in a straight line, and so can be visualized as the belt of the hunter’s clothing. In the Northern hemisphere, they are best visible in the early night sky during the winter, in particular the month of January at around 9.00 pm
Orion’s seven brightest stars form a distinctive asterism, or pattern, in the night sky—Rigel, Betelgeuse, Bellatrix and Saiph form a large roughly rectangular shape, in the centre of which lie the three stars of Orion’s Belt—Alnitak, Alnilam and Mintaka. Descending from the ‘belt’ is a smaller line of three stars (the middle of which is in fact not a star but the Orion Nebula), known as the hunter’s ‘sword’.
Many of the stars are luminous hot blue supergiants, with the stars of the belt and sword forming the Orion OB1 Association. Standing out by its red hue, Betelgeuse may nevertheless be a runaway member of the same group.