When Johannes Bayer in 1603 designed a system where the brightest star in a constellation was allocated the first letter of the Greek alphabet alpha then the next brightest beta until finally reaching the 24th or last letter of the Greek alphabet omega. When he ran out of Greek letters he moved onto lower case Roman letters then onto upper case, rarely used today. They do pop up occasionally in Perseus a cluster is still called “h Persei”, however the best known example is P Cygnus.
P Cygnus is an amazing star at around magnitude 5 it does not attract much attention on the constellation of Cygnus, In reality it is one of the most luminous stars in Cygnus. It lies at a distance of about 5,500 light years. Before the end of the 16th century it was unknown but in 1600 it was seen as a 3rd magnitude star. Bayer labelled the star P on his Uranometria star atlas of 1603. By 1626 it had faded below naked eye visibility and brightened again in 1655 and again faded in 1662. There was another outburst in 1665 but since 1715 it has been seen as a star of around magnitude 5.0
P Cygnus appears to be a star in a permanent novae state. The star is loosing mass at a very high rate and is surrounded by a faint nebula that has been created over the past 900 years. This nebula has been created due to eruptions over the past 2,400 to 20,000 years. P Cygnus is a hyper giant luminous blue variable stars in the same class as eta Carina. Due to its mass it might evolve into a red supergiant or could stay as a blue supergiant no one is sure at the moment, however it will end its life in a massive supernova explosion. We can be sure that P Cygnus still has a very eruptive future.