The night sky, with its vast expanse of twinkling stars and other celestial objects, has captivated humanity since the dawn of time. But what are the differences between the various phenomena we see when we look skywards?
Amongst the most stunning dark skies’ wonders are constellations, which are groups of visible stars positioned in such a way that they form a pattern recognisable to the human imagination. Astronomers have formally defined eighty-eight constellations, each representing animals, objects or mythological creatures.
Both Orion and Cassiopeia are constellations. Orion’s brightest stars form the shape of an hourglass and are best visible in the winter months of the Northern Hemisphere and the summer months of the Southern Hemisphere. When connected with more of this constellation’s stars, this shape resembles a hunter holding a bow, hence the name. In Greek mythology, Orion was a giant huntsman placed among the stars by the gods.
Cassiopeia, on the other hand, is easily recognisable due to its distinctive ‘W’ shape, formed by five bright stars. This constellation is named after the queen of Greek mythology and mother of Andromeda, who was punished for her vanity by being placed in the skies tied to her throne and upside down.
Not all groups of stars that form a pattern can be considered constellations; smaller clusters of stars are called ‘asterisms’, and they are not officially categorised in astronomy. While they can be part of a constellation, they are a more general concept and can simply comprise a few stars that form very simple shapes.
The Plough, also called the Big Dipper, is an asterism formed by seven bright stars in the Ursa Major constellation. Its shape resembles a saucepan, with stars forming the pan and the handle. However, it also looks like the farm tool used to loosen the soil before sowing seeds.
In the northwest of the constellation Taurus, the Seven Sisters star cluster, also known as the Pleiades, is one of the closest to Earth and among the most obvious to the naked eye. It comprises over a thousand stars that are loosely bound by gravity and that move across the sky in the same direction. In Greek mythology they are the Titan Atlas’ seven daughters transformed into a group of stars.
