Caelum is a faint constellation in the southern sky, introduced in the 1750s by Nicolas Louis de Lacaille. Its name means "the chisel" in Latin, and it was formerly known as Caelum Scalptorium ("the engraver's chisel"). It is the eighth-smallest constellation, and subtends a solid angle of around 0.038 steradians, just less than that of Corona Australis. Due to its small size and location away from the plane of the Milky Way, Caelum is a rather barren constellation, with few objects of interest. The constellation's brightest star, Alpha Caeli, is only of magnitude 4.45, and only one other star (Gamma1 Caeli) is brighter than magnitude 5. Other notable objects in Caelum are RR Caeli, a binary star with one planet approximately 20.13 parsecs (65.7 ly) away; X Caeli, a Delta Scuti variable that forms an optical double with Gamma1Caeli; and HE0450-2958, a Seyfert galaxy that at first appeared as just a jet with no host galaxy visible.
Caelum is bordered by Dorado and Pictor to the south, Horologium and Eridanus to the east,Lepus to the north, and Columba to the west. Covering 125 square degrees, it ranks 81st of the 88 modern constellations in size. It appears prominently in the southern sky during the Southern Hemisphere's summer, and the whole constellation is visible for at least part of the year to observers south of latitude 41°N.
Due to its small size and location away from the plane of the Milky Way, Caelum is rather devoid of deep-sky objects, and contains no Messier objects. The only deep-sky object in Caelum to receive much attention is HE0450-2958, an unusual Seyfert galaxy. Originally, the jet's host galaxy proved elusive to find, and this jet appeared to be emanating from nothing. Although it has been suggested that the object is an ejected supermassive black hole, the host is now agreed to be a small galaxy that is difficult to see due to light from the jet and a nearby starburst galaxy.
HGS Session References
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Found in HGS Manual on Page 108 Found in HGS Manual on Page 115