Constellations are not real!
The first thing you need to know is that constellations are
not real. Constellations are imaginary things that poets, farmers and astronomers
have made up over the past 6,000 years or so. The real purpose for the constellations is to
help remind us which stars are which in the sky.
On a really dark night away from city lights, you can see about a thousand to fifteen
hundred stars. Trying to identify them is hard. The 88 official constellations help by
breaking up the sky into more manageable sections. The constellations are mnemonics, or
For example, if you spot three bright stars in a row on a winter evening, you might realize
that you're looking at Orion. Then, the rest of the constellation falls into place: Betelgeuse
is in Orion's left shoulder and Rigel is in his foot.
Once you recognize Orion, you might remember that his Hunting Dogs are nearby. You could
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.
A sky atlas would show you a diagram like the black and white graphic on the left. Obviously,
this is very different from the photo above. This type of schematic denotes different star
brightnesses with different sized stars. Also, there is a standard way of connecting the stars
that allows astronomers and others to quickly tell what they are looking at. In almost every
star atlas, you will see Orion drawn with these same lines.
Further, every star on the chart is labeled. This chart is useful because it accurately shows
the relative positions of the stars in this small region of the sky.
Objects other than stars are 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 we can't see without a telescope. M42 is the Great Orion Nebula - the red splotch in
Orion's Sword in the photo above.