by Ron Kurtus (revised 23 November 2004)
A constellation in astronomy is a group of stars in our Milky Way galaxy that form a recognizable shape or figure. In some constellations, the "star" is actually another galaxy, when observed through a telescope.
Many constellations were named by ancient Greeks, who thought of them as related to gods. The most popular constellations are the Big Dipper, Orion, and the Southern Cross.
Questions you may have about the constellations are:
- What is the Big Dipper?
- What is Orion?
- What is the Southern Cross?
This lesson will answer those questions.
The Big Dipper
The Big Dipper is an important constellation for determining the location of the North Star. It can be seen in the night sky throughout the northern hemisphere of the Earth and in the northern part of the southern hemisphere.
The Big Dipper looks like a ladle or pot you would dip in a bucket of water. It is really part of a larger constellation called Ursa Major (Latin for the big bear). The stars that make up the bear are not too bright, so the dipper is more prominent.
You can see the handle of the Big Dipper and its pot
What is interesting about this constellation is that if you follow the two stars at the edge of the pot (on the right side in the picture), they point to the North Star. In fact, the Big Dipper rotates in a large circle around the North Star each night, as the Earth rotates on its axis.
Follow the front edge of the Big Dipper to the North Star
Both the Big Dipper and the North Star are used for navigation at night.
When you go to the movies, you may see a show produced by Orion Pictures. They always start by showing the Orion constellation. This constellation is supposed to represent Orion, the hunter.
You can see Orion's belt and sword
The four stars near the corners of the picture represent Orion's arms and legs. The three diagonal stars near the middle are supposed to be his belt. Below them are a line of dimmer stars almost going straight down. These are supposed to be the hunter's sword.
The Southern Cross is a major constellation in the sky of the southern hemisphere. It can be seen in the night sky throughout the southern hemisphere of the Earth and in the southern part of the northern hemisphere, below latitude 30. For example, New York City is at near latitude 40, so it is too far north to see the Southern Cross.
Four stars of the Southern Cross
This constellation is near the South Celestial Pole, around which the stars in the southern sky rotate. The Southern Cross is used for navigation in the southern hemisphere.
Australia and New Zealand have versions of the Southern Cross in their national flags.
A constellation is a group of stars that form a figure. The Big Dipper, Orion, and the Southern Cross are major constellations. You should try to find some constellations in the night sky.
Look up and reach for the stars
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Constellations in Astronomy