To the Land of Dreams: Apus

Apus is a small constellation in the southern sky. Covering 206.3 square degrees, and hence 0.500% of the sky, it ranks 67th of the 88 modern constellations by area. Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 7°N. It is bordered by Ara, Triangulum Australe and Circinus to the north, Musca and Chamaeleon to the west, Octans to the south, and Pavo to the east. In the equatorial coordinate system, the right ascension coordinates of Apus lie between 13h 49.5m and 18h 27.3m, while the declination coordinates are between -67.48° and -83.12°.

Apus seen in the Uranographia of Johann Bode (1801), where it was given the alternative title of Avis Indica, the Indian bird, referring to its habitat of the East Indies. The bird’s tail originally extended closer to the south celestial pole at lower left, as shown on Johann Bayer’s southern star chart of 1603, but was clipped by Lacaille in the 1750s to make room for Octans.

[http://www.ianridpath.com/startales/apus.htm]

Apus was first defined by Petrus Plancius, in the late 16th century, who called the constellation ‘Paradysvogel Apis Indica.’ The first word is Dutch for ‘bird of paradise’ but the others are Latin for ‘Indian Bee.’ Apis (Latin for ‘bee’) is presumably an error for avis (‘bird’).The name Apus means ‘no feet’ in Greek, and this referred to the Western misconception that the bird-of-paradise had no feet, which arose because the only specimens available in the West had their feet and wings removed.

When the Ming Dynasty Chinese astronomer Xu Guangqi adapted the European southern hemisphere constellations to the Chinese system in The Southern Asterisms, he combined Apus with some of the stars in Octans to form the ‘Exotic Bird’ (Yìquè).

[http://space.about.com/od/starsplanetsgalaxies/ig/Constellations-Pictures/apus.htm]

[http://www.universetoday.com/19562/apus/]

Within the constellation’s borders, there are 39 stars brighter than or equal to apparent magnitude 6.5. Alpha Apodis is an orange giant 447 ± 8 light years away from Earth, with a magnitude of 3.8. It spent much of its life as a blue-white main sequence star before expanding, cooling and brightening as it used up its core hydrogen, now shining with a luminosity approximately 928 suns, with a surface temperature of 4312 K.

Beta Apodis is an orange giant 157 ± 2 light years away, with a magnitude of 4.2. It is around 1.84 times as massive as the Sun, with a surface temperature of 4677 K.

Gamma Apodis is a yellow giant of spectral type G8III located 156 ± 1 light-years away, with a magnitude of 3.87. It is approximately 63 times as luminous the Sun, with a surface temperature of 5279 K.

Delta Apodis is a double star with a separation of 103 arcseconds. Delta1 is a red giant star located 760 ± 30 light years away. It is a semiregular variable that varies from magnitude +4.66 to +4.87, with pulsations of multiple periods of 68.0, 94.9 and 101.7 days. Delta2 is an orange giant star located 610 ± 30 light years away, with a magnitude of 5.3. The separate components can be resolved with binoculars, a telescope, or the naked eye.

R Apodis

The red giant once was seen as a longperiodic variable. This now is debatable, probably it doesn't change its luminosity. Admittedly the star is scarcely explored. Constellation: Apus; Distance: 428 light-years; Spectral class: K4; Visual magnitude: 5.38; Luminosity: circa 1000 * Sun.

[https://jumk.de/astronomie/big-stars/r-apodis.shtml]

Two star systems have had exoplanets discovered by doppler spectroscopy, and the substellar companion of a third star system- the sunlike star HD 131664- has turned out to be a brown dwarf with a predicted mass of the companion to 23 times that of Jupiter (minimum of 18 and maximum of 49 Jovian masses). HD 134606 is a yellow sunlike star of spectral type G6IV that has begun expanding and cooling off the main sequence. Three planets orbit it with periods of 12, 59.5 and 459 days, successively larger as they are further away from the star. HD 137388 is another star- of spectral type K2IV- that is cooler than the Sun and has begun cooling off the main sequence. Around 47% as luminous and 88% as massive as the Sun, with 85% of its diameter, it is thought to be around 7.4 ± 3.9 billion years old. It has a planet that is 79 times as massive as the Earth and orbits its sun every 330 days at an average distance of 0.89 AU.

Hubble Space Telescope image of the central region of NGC 6101

[https://en.wikipedia.org/wiki/NGC_6101]

The most prominent deep-sky objects in Apus include the globular clusters NGC 6101 and IC 4499 as well as the spiral galaxy IC 4633. NGC 6101 is a 14th magnitude globular cluster, located seven degrees north of Gamma Apodis. IC 4499 is a loose globular cluster in the medium-far galactic halo. Its apparent magnitude is 10.6, and it is unique because it is younger than most other globular clusters in the same region as determined by its metallicity.