Aquila (constellation)

Aquila is a stellar constellation. Its name is Latin for 'eagle' and it is commonly represented as such. In mythology, Aquila was owned by the Roman god Jupiter and performed many tasks for him.

Aquila lies just a few degrees North of the celestial equator. The alpha star, Altair, is a vertex of the Summer Triangle asterism. The constellation is best seen in the summer as it is located along the Milky Way. Because of this location along the line of our galaxy, many clusters and nebulae are found within its borders, but they are dim and there are few galaxies.

History

Aquila was one of the 48 constellations described by the 2nd century astronomer Ptolemy. It had been earlier mentioned by Eudoxus in the 4th century BC and Aratus in the 3rd century BC. It is now one of the 88 constellations defined by the International Astronomical Union. The constellation was also known as Vultur volans (the flying vulture) to the Romans, not to be confused with Vultur cadens which was their name for Lyra.

Ptolemy catalogued nineteen stars jointly in this constellation and in the now obsolete constellation of Antinous, which was named in the reign of the emperor Hadrian (AD 117–138), but sometimes erroneously attributed to Tycho Brahe, who catalogued twelve stars in Aquila and seven in Antinous. Hevelius determined twenty-three stars in the first^[1] and nineteen in the second.^[2]

The Greek Aquila is probably based on the Babylonian constellation of the Eagle (MUL.A.MUSHEN), which is located in the same area as the Greek constellation.^[3]

Named stars

Notable features

Stars

Aquila, which lies in the Milky Way, contains many rich starfields.

• α Aql (Altair): this multiple star system (3 components) has 0.77m and is of spectral type A7 V. It has a parallax of 0.23", and consequently is about eight times as bright as the Sun.
• β Aql (Alshain): its spectral type is G8 IV and it shines with an apparent brightness of 3.71m. Like Altair, it too is a multiple star system with three components.
• γ Aql (Tarazed): spectral type K3 II; 2.72m.
• η Aql. This short-period variable star is one of the brightest classical Cepheids; its brightness varies between 3.48 mag and 4.39 mag every 7.177 days.
• 15 Aql. This double star is a yellow K star of 5.4 mag accompanied by a 7th mag star; it can easily be observed with small telescopes.
• ρ Aql moved across the border into neighboring Delphinus in 1992.

Novae

Two major novae have been observed in Aquila: the first one was in 389 BC and was recorded as being as bright as Venus; the other (Nova Aquilae 1918) briefly shone brighter than Altair, the brightest star in Aquila.

Deep-sky objects

Three interesting planetary nebulae lie in Aquila:

• NGC 6804 shows a small but bright ring
• NGC 6781 which bears some resemblance with the Owl Nebula in Ursa Major.
• NGC 6751: also known as the Glowing Eye, a planetary nebula

More deep-sky objects:

• NGC 6709: an open cluster of 6.7m located five degrees southwest of Zeta Aquilae
• NGC 6755: an open cluster of 7.5m; it is made up of about a dozen stars with magnitudes 12 through 13
• NGC 6760: a globular cluster of 9.1m
• NGC 6749: an open cluster
• NGC 6778: planetary nebula
• NGC 6741: planetary nebula
• NGC 6772: planetary nebula

Other

NASA's Pioneer 11 space probe, which flew by Jupiter and Saturn in the 1970s, is expected to pass near the star Lambda (λ) Aquilae in about 4 million years.^[4]

Illustrations

In illustrations of Aquila that represent it as an eagle, a nearly straight line of three stars symbolizes part of the wings. The center and brightest of these three stars is Altair. The tips of the wings extend further to the southeast and northwest. The head of the eagle stretches off to the southwest.

Mythology

According to Gavin White, the Babylonian Eagle carried the constellation called the Dead Man (LU.USH) in its talons. The author also draws a comparison to the Classical stories of Antinous and Ganymede.^[5]

In classical Greek mythology, Aquila was identified as Αετός Δίας (Aetos Dios), the eagle that carried the thunderbolts of Zeus and was sent by him to carry the shepherd boy Ganymede, whom he desired, to Mount Olympus; the constellation of Aquarius is sometimes identified with Ganymede.

In the Chinese love story of Qi Xi, Niu Lang (Altair) and his two children (β and γ Aquilae) are separated forever from their wife and mother Zhi Nu (Vega) who is on the far side of the river, the Milky Way.

In Hinduism, the constellation Aquila is identified with the half-eagle half-human deity Garuda.^[6][7]

Equivalents

In Chinese astronomy, ζ Aql is located within the Heavenly Market Enclosure (天市垣, Tiān Shì Yuán), and the other stars of the constellation are placed within the Black Tortoise of the North (北方玄武, Běi Fāng Xuán Wǔ).

Namesakes

Two United States Navy ships, USS Aquila (AK-47) and USS Aquila (PHM-4), are named after the constellation.

See also

Aquila (Chinese astronomy)

References

Sources

•  This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press. 
• Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0007251209. Princeton University Press, Princeton. ISBN 978-0691135564.

External links

• NightSkyInfo.com: Constellation Aquila
• Star Tales – Aquila
• The Deep Photographic Guide to the Constellations: Aquila
• WIKISKY.ORG: Aquila constellation

Coordinates: 20^h 00^m 00^s, +05° 00′ 00″