Asterisms Guides to the Sky

What is an Asterism? An Asterism is a group of bright stars that form a pattern but are not a constellation They are either: Composed of stars that are parts of other different constellations…or… Only part of a constellation.

Even when we can’t see many entire constellations in our urban night sky, we can usually spy one of these five asterisms!

The Summer Triangle The Summer Triangle can be seen in the sky from mid-spring to mid-fall. Its stars are part of different constellations: Vega, the brightest --- Lyra (the Lyre) Deneb ---Cygnus (the swan) Altair --- Aquila (the eagle) (Copy the next slide as a sketch…)

The Winter Triangle The Winter Triangle is an equilateral triangle which can be seen at night from mid-fall to mid-spring. Its stars are also in different constellations: Betelgeuse ,a red star ---Orion (the Hunter) Sirius, the brightest of all stars --- Canis Major (the big dog) Procyon --- Canis Minor (the little dog) (Copy the next slide.)

Orion’s Belt These are three stars in nearly a straight line. They appear in early fall and last until early spring, and lie across the Celestial Equator

Follow them and find…. Going down… Sirius and Canis Major Going up… Aldebaran, the “red eye” of Taurus the Bull, on the ecliptic, And farther up… the Pleiades, or “Seven Sisters.” (And again, copy the next slide!)

The Big Dipper …is part of the larger constellation Ursa Major (the Big Bear). It never sets if viewed from most of the Northern Hemisphere. The star, Mizar, at the bend in the ‘handle,’ is really two stars that orbit each other. The two stars that form the edge of the bowl are called the “Pointer Stars” and point toward Polaris, the North Star.

The Little Dipper …is part of the constellation Ursa Minor, the Little Bear. It never sets if viewed from most of the Northern Hemisphere. Its handle is a smooth curve and ends with Polaris, the North Star, which lies less than a degree from the North Celestial Pole. And, once again, copy the next slide!