What does a Greek letter in front of a constellation signify?

Alpha-Cassiopeia, for example. What two things does this tell you?What does a Greek letter in front of a constellation signify?It ranks the stars of a constellation in order of decreasing apparent magnitude. So Alpha Cassiopeiae is supposed to be the brightest star of the constellation Cassiopeia.



However, and here is where this question becomes amusing, Alpha Cassiopeiae is at present only the 2nd brighest star in the constellation Cassiopeia. The reason is that Gamma Cassiopeiae is a variable star and is the brighter star since the 1930s.



Note that it's Alpha CassiopeiaE, which translates as Alpha *of* Cassiopeia.What does a Greek letter in front of a constellation signify?It identifies a specific star within a constellation and is known as the Bayer designation. Contrary to popular belief alpha does not always indicate the brightest star since the classification predates precise photometry. Instead, generally all the first magnitude stars were labelled, followed by all the second magnitude and so on. This lead to examples such as Orion, where Beta (Rigel) is always brighter than Alpha (Betelgeuse). However, even that is only a general trend. In some constellations the stars appear to be lettered by position and in still others no discernible pattern is apparent.What does a Greek letter in front of a constellation signify?The brightest stars in each constellation are named using Greek letters. In most cases the brightest star is named Alpha, the second brightest, Beta, the third Gamma, and so on down the Greek alphabet. Some constellations are notable exceptions; for example the bright stars which form the Big Dipper in Ursa Major are named from west to east in increasing alphabetical order. Note that the constellation name should be in the Latin genitive case, meaning "of", so "Alpha Cassiopeiae" = "Alpha of Cassiopaeia," "Beta Geminorum" = "Beta of Gemini," etc. These Greek letters are often called Bayer letters or Bayer designations after Johann Bayer, 17th century astral cartographer.



I know it's a bit of a pain to need to know the Greek alphabet and Latin genitive forms of the constellation names, but its kind of interesting!What does a Greek letter in front of a constellation signify?
It represents a star in the constellation. Alpha Cassiopeiae is the brightest star in Cassiopeia with a magnitude 2.24. Johann Bayer was the first to label the brightest stars of a constellation with Greek letters in 1603.