The Greek alphabet

The Greek alphabetThe greek alphabet is used to determine which star is brighter in a constellation. Look at Orion. The brightest is always alpha, the second brighter is beta and so forth, next to be followed by the constellation name. This rule apply to all constellation except Ursa major, which is according to their order in the night sky. This method of naming was designated by a German astronomer Johann Bayer.

Flamsteed designations is sometimes used too. Instead of using greek letters, Flamsteed designation used numbers according to an increasing right ascension in a constellation. Although this method is somewhat less popular than the previous Bayers deignation.

Astronomical Catalogues

There are many astronomical catalogs, but in most beginners catalogs, Messier and NGC catalogs are the most frequently used.

M = Stand for Messier

NGC = New General Catalogue

The M followed by numbers. It referred to any cometlike objects. For example M1 is referring to Crab nebula and M31 is referring andromeda galaxy. It is not something very uncommon to see one object but with more than one designations.