Apus constellation is located in the southern hemisphere. It is a small constellation that represents the bird of paradise. The name of the constellation is derived from the Greek word apous, which means “footless.” (Birds of paradise were at one point in history believed to lack feet.) There are no myths associated with the constellation.
Apus was created by the Dutch astronomer and cartographer Petrus Plancius from the observations of Dutch navigators Pieter Dirkszoon Keyser and Frederick Houtman, and first catalogued by Plancius in the late 16th century.
Apus is home to two notable deep sky objects: the globular clusters NGC 6101 and IC 4499. The constellation also contains the galaxies IC 4633 and IC 4635.
Facts, location and map
Apus is the 67th constellation in size, occupying an area of 206 square degrees. It lies in the third quadrant of the southern hemisphere (SQ3) and can be seen at latitudes between +5° and -90°. The neighboring constellations are Ara, Chamaeleon, Circinus, Musca, Octans, Pavo, and Triangulum Australe.
Apus has two star systems with known exoplanets, HD 131664 (G3V) and HD 134606 (G6IV).
The brightest star in the constellation is Alpha Apodis. The nearest star, HD 128400, lies at a distance of 66.36 light years from Earth. Apus does not have any stars brighter than magnitude 3.00 or located within 10 parsecs (32.6 light years) of Earth.
Apus does not have any Messier objects and there are no meteor showers associated with the constellation.
Apus contains one formally named star. The star name approved by the International Astronomical Union (IAU) is Karaka (HD 137388).
Apus was originally named Paradysvogel Apis Indica by Petrus Plancius, who created and introduced the constellation. Paradysvogel means “the bird of paradise” in Dutch, and Apis Indica is Latin for “indian bee.” Apis, the word for “bee,” was presumably used in error and the constellation should have been named Avis, which means “bird.”
The constellation was also called Apis Indica in Bayer’s Uranometria, while other astronomers, like Johannes Kepler, referred to it as Avis Indica, as Kepler did in his Rudolphine Tables in 1627. As a result of the confusion, Avis Indica was renamed to Apus, and Apis, the constellation representing the bee, became Musca, the fly.
French astronomer Lacaille called the constellation Apus in his chart of the southern skies published in 1763, but both Apis and Avis continued to be used well into the 19th century.
Major stars in Apus
α Apodis (Alpha Apodis)
With an apparent magnitude of 3.825, Alpha Apodis is the brightest star in Apus. Approximately 410 light years distant, it is classified as a K-type giant.
γ Apodis (Gamma Apodis)
Gamma Apodis is the second brightest star in the constellation, with an apparent magnitude of 3.872. It is a yellow G-type giant star, approximately 160 light years distant.
δ Apodis (Delta Apodis)
Delta Apodis is a binary star, approximately 800 light years distant. The brighter component, Delta-1 Apodis, is an irregular variable star and has an apparent magnitude that varies between 4.66 and 4.87. Delta-1 Apodis is an M-type red giant star.
Delta-2 Apodis is an orange K-type giant star with an apparent magnitude of 5.27. It is 102.9 arc seconds away from the primary star.
κ Apodis (Kappa Apodis)
Kappa Apodis is a Bayer designation denoting two star systems, Kappa-1 Apodis (HR 5730) and Kappa-2 Apodis (HR 5782).
Kappa-1 Apodis is a blue-white B-type subgiant approximately 1020 light years distant. It is a Gamma Cassiopeiae type variable, a fast rotating shell star with variations in luminosity caused by the outflow of matter, and has a mean apparent magnitude of 5.40. Its luminosity varies between 5.43 and 5.61. The star has a companion, a magnitude 12 orange K-type subgiant, lying 27 arc seconds away.
Kappa-2 Apodis is a binary star composed of a blue-white B-type giant and an orange K-type main sequence dwarf 15 arc seconds away, with a 13th magnitude optical companion 15 arc seconds away. The primary star has an apparent magnitude of 5.64 and the orange dwarf, 12.5.
Other notable stars:
β Apodis (Beta Apodis) is an orange K-type giant star, located about 158 light years from Earth. It has an apparent magnitude of 4.23 and is the third brightest star in Apus.
ζ Apodis (Zeta Apodis) is an orange K-type giant, about 312 light years distant. It has an apparent magnitude of 4.76.
η Apodis (Eta Apodis) is classified as an Am star or metallic-line star, an A-type star that is chemically peculiar and whose spectrum has strong absorption lines of some metals and deficiencies of others. Eta Apodis is emitting excess infrared radiation, possibly as a result of a debris disk orbiting the star at a distance of 31 AU.
ε Apodis (Epsilon Apodis) is a blue-white B-type main sequence star, approximately 551 light years away. It is another Gamma Cassiopeiae type variable, with a mean apparent magnitude of 5.06. Its brightness varies by 0.05 magnitudes.
Deep sky objects in Apus
NGC 6101 is a small globular cluster in Apus that can be observed through a 4.5-inch telescope. It lies seven degrees north of Gamma Apodis and has an apparent magnitude of 9.2.
IC 4499 is another small, faint globular cluster. It is the southernmost globular cluster in the sky, which is to say that it is the globular cluster closest to the south celestial pole. It can be seen in an eight inch telescope as a small patch.
Other notable deep sky objects
IC 4633, IC 4635 and NGC 6392 are the brightest galaxies that can be seen in the constellation.