Apus is a small, faint southern hemisphere constellation whose brightest star, Alpha Apodis, has a visual magnitude of just 3.825. The constellation was one of 12 created in the 16th-century by Petrus Plancius in order to fill in the gaps around the south celestial pole left over from ancient times, with his new constellations based upon the observations of Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman. Apus derives from the Greek for “without feet”, because the bird-of-paradise it represented was mistakenly thought to lack feet. There are no Messier objects or meteor showers associated with the constellation.
Apus is the 67th largest of the 88 recognized constellations, and takes up an area of 206 square degrees, or 0.5% of the night sky. It can be seen by observers located between +5° and -90° of latitude, although best seen in July, and can be found north-east of Octans, which is the constellation which marks the South Celestial Pole.
Johann Bayer Family
Apus is a member of the Johann Bayer family of constellations, together with Chamaeleon, Dorado, Grus, Hydrus, Indus, Musca, Pavo, Phoenix, Tucana, and Volans.
– Alpha Apodis, the constellation’s brightest star, is an orange giant (K2.5III) situated 410 light years from our solar system that shines with an apparent magnitude of 3.825. It is around 48 times bigger than our sun, and 980 times more luminous.
– Gamma Apodis, the second brightest star in Apus, is a yellow giant (G9 III) found 160 light years distant of magnitude 3.872. It is around 10 times bigger than the Sun.
– Beta Apodis, the constellation’s third brightest star, is an orange giant (K0 III) located 158 light-years from Earth with an apparent magnitude of 4.24. It is about 11 times bigger than the Sun.
– Delta Apodis is a binary system situated 800 light years away whose apparent magnitude varies from between 4.66 and 4.87. Its main component, Delta-1 Apodis, is a red giant, while its companion, Delta-2 Apodis is an orange giant.
Other stars of interest in Apus includes the multiple star system Kappa Apodis; the blue-white star Epsilon Apodis; the orange giant Zeta Apodis; the red giants Theta Apodis and NO Apodis; the metallic-line star Eta Apodis; while stars with planets discovered in Apus includes HD 134606 and HD 137388.
Notable Deep-Sky Objects
– NGC 6101 is a globular cluster that is found 50,000 light-years away and shines with an apparent magnitude of 9.2. It is about 13 billion years old, 160 light-years wide, and hosts a high concentration of blue stragglers, which are stars which stay on the main sequence phase for longer than expected, possibly due to collisions or mass transfer with other stars.
Other objects of interest in Apus includes IC 4499, a 12 billion years old globular cluster located 613 away of magnitude 9.76; as well as the galaxies IC 4633, IC 4635 and NGC 6392.