Apus

Apus is a faint constellation in the southern sky, first defined in the late 16th century. Its name means "no feet" in Greek, and it represents a bird-of-paradise (which were once believed to lack feet). Its genitive is "Apodis".

History

Apus was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman. It first appeared on a 35 cm diameter celestial globe published in 1597 or 1598 in Amsterdam by Plancius with Jodocus Hondius.^[1][3][4] Plancius called the constellation Paradysvogel Apis Indica; the first word is Dutch for "bird of paradise", of genus Pteridophora, but the others are Latin for "Indian Bee". Apis (Latin for "bee") is presumably an error for avis ("bird").^[1][4]

The name Apus is derived from the Greek apous, meaning "without feet". 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.^[1] Such specimens began to arrive in Europe in 1522, when the survivors of Ferdinand Magellan's expedition brought them home.^[5]

After its introduction on Plancius's globe, the constellation's first known appearance in a celestial atlas was in Johann Bayer's Uranometria of 1603, where it was called "Apis Indica".^[1][4]

Richard Allen reports Semler's assertion that de Houtman, who observed the southern constellations from the island of Sumatra, took his ideas for the formation of Apus (as well as Phoenix and Indus) from the Chinese, who knew the stars of Apus as the "Little Wonder Bird",^[6] and that Semler's assertion was disputed by Ideler (though Ideler acknowledged the Chinese constellations).

Characteristics

Covering 206.3 square degrees and hence 0.500% of the sky, Antlia ranks 67th of the 88 modern constellations by area.^[7] Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 7°N.^{[7][lower-alpha 1]} 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. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Aps'.^[8] The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of six segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 13^h 49.5^m and 18^h 27.3^m, while the declination coordinates are between -67.48° and -83.12°.^[2]

Notable features

The constellation Apus as it can be seen by the naked eye.

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.

Stars

Within the constellation's borders, there are 39 stars brighter than or equal to apparent magnitude 6.5.^{[lower-alpha 2][7]}

Alpha Apodis is an orange giant 411 light years away, with a magnitude of 3.8.^[3][4] Beta Apodis is an orange giant 158 light years away, with a magnitude of 4.2.^[3] Gamma Apodis is an orange giant 160 light years away, with a magnitude of 3.9.^[3] Delta Apodis is a double star with a separation of 103 arcseconds.^[4] δ¹ is a red giant star located 765 light years away, with a magnitude of 4.7. δ² is an orange giant star^[4] located 663 light years away, with a magnitude of 5.3. The separate components can be resolved with binoculars, a telescope, or the naked eye.^[3] Theta Apodis is a variable red giant at a distance of 328 light years with a period of approximately 4 months,^[3] or 109 days.^[4] It has a maximum magnitude of 4.8 and a minimum magnitude of 6.1.^[4]

NO Apodis is a red giant of spectral type M3III that varies between magnitudes 5.71 and 5.95.^[10] Located around 883 light-years distant, it shines with a luminosity approximately 2059 times that of the Sun and has a surface temperature of 3568 K.^[11]

Deep-sky objects

Globular cluster IC 4499 taken by Hubble Space Telescope.^[12]

• NGC 6101 is a 14th magnitude globular cluster, located seven degrees north of γ Aps.^[4]
• IC 4499 is a loose globular cluster in the medium-far galactic halo.^[13] Its apparent magnitude is 10.6,^[14] and it is unique because it is younger than most other globular clusters in the same region as determined by its metallicity.^[13]
• IC 4633 is a very faint spiral galaxy ^[4] surrounded by a vast amount of Milky Way line-of-sight Integrated Flux Nebulae.

Equivalents

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" (異雀, Yìquè).^[15]

Notes

References

Citations

References

• Ridpath, Ian (2001), Stars and Planets Guide, Princeton University Press, ISBN 0-691-08913-2 
• Ridpath, Ian (2007), Stars and Planets Guide, Wil Tirion (4th ed.), Princeton University Press, ISBN 978-0-691-13556-4 
• Staal, Julius D.W. (1988), The New Patterns in the Sky: Myths and Legends of the Stars, The McDonald and Woodward Publishing Company, ISBN 0-939923-04-1 

External links

Wikimedia Commons has media related to Apus.

• The Deep Photographic Guide to the Constellations: Apus
• NightSkyInfo.com: Constellation Apus
• WIKISKY.ORG: Apus on WIKISKY
• Star Tales – Apus
• Apus Constellation at Constellation Guide

Coordinates: 16^h 00^m 00^s, −75° 00′ 00″