Caelum is a small and faint constellation in the Southern sky, and ranks 81st out of 88 constellations in size. It occupies ony 125 square degrees, which is approximately 0.3% of the night sky. Unfortunately, it has no star brighter than magnitude 4, with only 2 brighter than magnitude 5.
Due to its small size and the faintness of stars within it, the author believes that there is no foolproof way to find Caelum. Canopus of the Carina constellation can serve as a useful reference for its general location.
This is a rough drawing of Caelum, with its neighbouring constellations.
Amongst the stars in Caelum, the author believes X Caeli to be the most interesting. X Caeli is a Delta Scuti variable star which can be used as a standard candle. A Delta Scuti variable is essentially a type of young pulsating star which follows a period-luminosity relationship, where a period luminosity relationship links the luminosity of pulsating variable stars with their periods. X Caeli is also a contact binary, indicating that the stars are so close that they share envelopes. In a contact binary, the stars have both filled up their Roche lobes, allowing the more massive star to transfer matter and luminosity to the less massive star.
Up next is Camelopardalis.