Constellations - star patterns

Looking at the Constellations

Constellations are not 'real'

They are imaginary things that poets, farmers, sailors and astronomers have made up over the past 6,000 years or more to help us tell which stars are which, nothing more.

On a really dark night, you can see about 1000 to 1500 stars. Trying to tell which is which is very difficult. Sorting them out into constellations helps by breaking up the sky into more manageable bits.

Constellations are used as memory aids by turning stars into dots for a dot-to-dot picture.

For example, if you spot three bright stars in a row in the winter evening, you might realize, "Oh! That's part of Orion!" Suddenly, the rest of the constellation falls into place and you can declare: "There's Betelgeuse in Orion's left shoulder and Rigel is his foot." And once you recognize Orion, you can remember that Orion's Hunting Dogs are always nearby. Then you might recognize the two bright stars in the upper and lower left of the photograph as Procyon in Canis Minor and Sirius in Canis Major, respectively.

When you look in a sky atlas, you might see diagrams like the one on the right:

Obviously, this is very different from the photo above. This type of diagram draws the stars as different sizes to represent different brightness. In addition, there is a standard way to connect the stars that allow astronomers and others who use charts like this to quickly tell what they are looking at. In almost every star atlas, you will see Orion drawn with these same lines.

Every star on the chart is labelled. This type of chart is useful because it accurately shows the relative positions of the stars in this small region of the sky. In addition, other things besides stars are also labelled on the chart. For example, Barnard's Loop on the left and M42 in the bottom middle are pointed out. Barnard's Loop is a cloud of faintly glowing gas, which can't be seen without a telescope. M42 is the Great Orion Nebula and it is the red splotch in Orion's Sword in the photo above.
 
 

Where did the constellation names come from?

Why would people want to remember the stars names? Farmers  invented the constellations. Why did they do that? Was it for some religious purpose?

Yes and no. Around the world, farmers know that for most crops, you plant in the spring and harvest in the fall. But in some regions, there is not much differentiation between the seasons. Since different constellations are visible at different times of the year, you can use them to tell what month it is. For example, Scorpius is only visible in the northern hemisphere's evening sky in the summer. Some historians suspect that many of the myths associated with the constellations were invented to help the farmers remember them. When they saw certain constellations, they would know it was time to begin the planting or the reaping.

This dependence on the sky became a strong part of many cultures. Perhaps there is something about the mystery of the night sky that makes people want to tell stories about the constellations. The picture at the left is an ornate star chart printed in 1835. Like the others, it shows the great hunter Orion. In this one, he is holding a lion's head instead of his traditional bow or shield. He has an eager look in his eye as he stalks Taurus, the Bull. Behind him, his faithful dog, Canis Major, is chasing Lepus, the Hare. Compare this picture to the photo near the top of the page. They are at about the same scale and they show the same stars. The constellations have changed over time. In our modern world, many of the constellations have been redefined so now every star in the sky is in exactly one constellation. In 1929, the International Astronomical Union (IAU) adopted official constellation boundaries that defined the 88 official constellations that exist today.

The graphics above are from "Constellations" by Motz and Nathanson and "Universe" by Kaufmann

So, constellations are:

• names for groups of stars that appear to form shapes in the sky.
• They were given their names many hundreds of years ago to help us remember which stars are which.
• We use constellations to divide up the sky;
• finding one can help us find another because constellations (being so far away from us) appear to move so slowly that, in our lifetime, they will always be found in about the same place

The Big Dipper - part of the constellation of Ursa Major or the Great Bear) The best known group of stars is the Big Dipper. The Big Dipper is a group of seven bright stars, 3 which form a handle and 4 which form a bowl.. The Big Dipper is not actually a constellation but is part of the constellation Ursa Major, or Great Bear.	Little Dipper - part of the constellation of Ursa Minor or the Little Bear The Little Dipper is a mirrored and smaller version of the Big Dipper. It can be found by looking directly up from the two outermost stars which form the bowl on the Big Dipper. These two stars point us to Polaris, the Pole Star (indicating the North Pole), which is at the end of the Little Dipper's handle.

 

	Orion Another well known constellation is Orion. Orion was an ancient Greek hunter and warrior and the constellation resembles this figure, with a club and a shield, and a sword dangling from his belt. The belt is usually the easiest part of Orion to spot, with three bright stars in a row. Can you find his belt in the picture below? Orion has more bright stars than any other constellation; the two brightest are Betelgeuse (shoulder) and Rigel (foot).
Cassiopeia Cassiopeia is found next to the Big Dipper and Orion. Its shape is easy to remember, a neat W, or M, formed by 5 bright stars. Cassiopeia is the mythological Queen of Ethiopia.
	The Pleiades Seven Sisters)   The Seven Sisters were said to be the daughters of Atlas and the objects of Orion's affection. As the name Seven Sisters implies, there are seven stars in this constellation but most people can only see six. The Pleiades is located between the constellations of Taurus and Perseus.
Sky Chart This chart shows some of the constellations mentioned above. In the middle you can see the Big Dipper, using this we can find several other constellations around it. As mentioned above, the side of the Big Dipper's bowl points to Polaris in the Little Dipper. The bottom of the bowl points to the constellation Gemini, the left side of the bowl to the constellation, Leo, and the handle to Bootes. Cassiopeia can also be seen in the top left corner. To find out more about any of the constellations mentioned here (and those which aren't) visit some of the sites listed below.

Links to other constellation web sites:

The Constellations and their Stars

I had very little authorship of this page. The information and illustrations of this page were taken from http://www.kn.pacbell.com/wired/fil/pages/samstarsanda.html on 26/11/00 . This site has sadly now ceased to operate and I could not contact the author for permission to post this excellent information..

LOJ November 2000 Amended March 2003