Constellations

What Are Constellations?

So just what are these constellations you keep hearing about? You may go outside some night and see all kinds of stars, and maybe you have even spotted the Big Dipper (northern hemisphere) or the Southern Cross (southern hemisphere), but what about Leo the Lion or Pisces the Fish? What are they?

Looking at the Constellations

The first thing you need to know is that constellations are not real!

When you look in a sky atlas, you might see diagrams like this:
Obviously, this is very different from the photo above. This type of schematic draws the stars as different sizes to represent different brightnesses. 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.

You might also notice that every star on the chart is labeled (sorry that it came out a little blurry). This 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 labeled 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.