The Apus constellation contains one formally named star — Karaka (HD 137388), as approved by the International Astronomical Union (IAU) — and also contains two star systems with known exoplanets, HD 131664 (G3V) and HD 134606 (G6IV).
Apus is not home to any stars brighter than magnitude 3.00 or located within 10 parsecs (32.6 light years) of Earth. The brightest star in Apus is Alpha Apodis and the nearest star is HD 128400 and lies at a distance of 66.36 light years from Earth. There are no Messier objects in Apus and no meteor showers are associated with the constellation.
History and Mythology
While there are no myths associated with Apus, which represents the bird of paradise, its name is derived from the Greek word apous, which means “footless”. Birds of paradise were, at one point in history, believed to lack feet.
The Apus Constellation was created by the Dutch astronomer and cartographer Petrus Plancius from the observations of Dutch navigators Pieter Dirkszoon Keyser and Frederick Houtman. It was first catalogued by Plancius in the late 16th century and he originally named it Paradysvogel Apis Indica.
“Paradysvogel” means “the bird of paradise” in Dutch, and “Apis Indica” is Latin for “indian bee”. It is thought that “Apis”, which means “bee”, was used in error, as the constellation represents a bird and not a bee.
In Bayer’s Uranometria, the constellation was named Apis Indica, but other astronomers referred to it as Avis Indica. Therefore, there was a lot of confusion and so the constellation was renamed to Apus. Apis, the constellation representing the bee, was renamed Musca, meaning “the fly”. The astronomer Lacille called the constellation Apus in his chart of the southern skies that he published in 1763.
Apus is a small constellation and the 67th largest constellation. It occupies 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°.
Its right ascension is 13h 51m 07.5441s – 18h 27m 27.8395s and its declination is −67.4800797° to −83.1200714°. It is best seen at 9pm during the month of July. Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 7°N.
Apus’ neighboring constellations are Ara, Chamaeleon, Circinus, Musca, Octans, Pavo, and Triangulum Australe and it belongs to the Johann Bayer family of constellations, along with Chamaeleon, Dorado, Grus, Hydrus, Indus, Musca, Pavo, Phoenix, Tucana and Volans.
Alpha Apodis is the brightest star in Apus and has an apparent magnitude of 3.825. It is an orange giant of spectral type K3III and is located around 410 light years away from us. It has a diameter that is 48 times that of the Sun and shines with a luminosity that is around 928 times that of the Sun. Alpha Apodis has a surface temperature of 4312 K.
Gamma Apodis is the second brightest star in the constellation and has an apparent magnitude of 3.872. It is a yellow giant of spectral type G8III and is located around 160 light years away from us. It is approximately 63 times as luminous the Sun, with a surface temperature of 5279 K.
Beta Apodis is an orange K-type giant star and the third brightest star in Apus. It has an apparent magnitude of 4.23 and is located around 158 light years away from Earth. It is around 1.84 times as massive as the Sun and has a surface temperature of 4677 K.
Delta Apodis is a binary star located around 800 light years away from us. It is composed of Delta-1 Apodis, an M-type red giant star and variable star with an apparent magnitude that varies between 4.66 and 4.87, and Delta-2 Apodis, an orange K-type giant star with an apparent magnitude of 5.27. The two stars are separated by 102.9 arc seconds and can be seen with the naked eye.
Epsilon Apodis is a blue-white B-type main sequence star and a Gamma Cassiopeiae type variable. It has a mean apparent magnitude of 5.06 and its brightness varies by 0.05 magnitudes. It is located around 551 light years away from us.
Zeta Apodis is the fifth brightest star in the constellation and has an apparent magnitude of 4.76. It is an orange giant of spectral type K1III, with a surface temperature of 4649 K and a luminosity 133 times that of the Sun. It is located around 312 light years away from us.
Iota Apodis is a binary star composed of two blue-white main sequence stars that orbit each other every 59.32 years. Of the spectral types B9V and B9.5 V, they are both over three times as massive as the Sun. The system is located 1,040 light years away from us.
Eta Apodis is a white main sequence star with an apparent magnitude 4.89. It 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. It is located around 140.8 light years away from us.
Eta Apodis is 1.77 times as massive, 15.5 times as luminous as the Sun and has 2.13 times its radius. It is also around 200 million years old. It is emitting an excess of 24 μm infrared radiation, which may be caused by a debris disk of dust orbiting at a distance of more than 31 astronomical units from it.
Theta Apodis is a cool red giant of spectral type M7 III that is also a semiregular variable, with a magnitude that varies by 0.56 magnitudes with a period of 119 days. It is located around 350 light years away from us and shines with a luminosity approximately 3879 times that of the Sun and has a surface temperature of 3151 K.
Kappa Apodis is a Bayer designation of two stars — Kappa-1 Apodis (HR 5730) and Kappa-2 Apodis (HR 5782).
Kappa-1 Apodis is a blue-white B-type subgiant that is also a Gamma Cassiopeiae type variable, a fast rotating shell star with variations in luminosity. Its mean apparent magnitude is 5.40 but its luminosity varies between 5.43 and 5.61. It has a companion located around 27 arc seconds away that is a magnitude 12 orange K-type subgiant.
Kappa-2 Apodis is a binary star composed of a blue-white B-type giant and an orange K-type main sequence dwarf. They are located 15 arc seconds from each other and a 3th magnitude optical companion is 15 arc seconds away from the companion. The primary star has an apparent magnitude of 5.64 and the companion has a magnitude of 12.5.
No Apodis is a red giant of spectral type M3III that varies between magnitudes 5.71 and 5.95. It shines with a luminosity estimated at 2059 times that of the Sun and has a surface temperature of 3568 K. It is located around 780 light years away from us.
S Apodis is a rare R Coronae Borealis variable, which an extremely hydrogen-deficient supergiant thought to have arisen as the result of the merger of two white dwarfs. It has a baseline magnitude of 9.7.
Deep Sky Objects
NGC 6101 is a small globular cluster located around 50,000 light-years distant from Earth, seven degrees north of Gamma Apodis. It has an apparent magnitude of 9.2 and can be observed through a 4.5-inch telescope. It is around 160 light-years across and 13 billion years old.
IC 4499 is a small, faint globular cluster and the southernmost globular cluster in the sky, meaning it is the globular cluster closest to the south celestial pole. Its apparent magnitude is 10.6 and it can be seen in an eight inch telescope as a small patch.
IC 4633 is a very faint spiral galaxy surrounded by a vast amount of Milky Way line-of-sight integrated flux nebulae — which are large faint clouds thought to be lit by large numbers of stars.
- The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is “Aps”.
- The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of six segments.
- Some Images created with the NightVision app – https://www.nvastro.com/nvj.html
- Some Images created with the Stelvision Sky Map https://www.stelvision.com/en/sky-map/
- Apus 1 – https://starregistration.net/constellations/apus-constellation.html
- Apus 2 – https://in-the-sky.org/data/constellation.php?id=4
- NGC 6101 – http://www.phys.ttu.edu/~ozprof/6101c.htm
- IC 4499 – https://theskylive.com/sky/deepsky/ic4499-object
- IC 4633 – http://members.pcug.org.au/~stevec/ic4633_STL6303_RC.htm