Aquila (constellation)

Aquila (Latin for Eagle), is one of the 48 constellations listed by Ptolemy and is now also part of the list of 88 constellations acknowledged by the IAU. It lies roughly at the celestial equator. The alpha star, Altair, is a vertex of the so-called "Summer Triangle".

Notable features

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

• α Aql: also known as Altair (ar. flying) this multiple star system (3 components) has 0.77m and is of spectral type A7 V.
• 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 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.

Notable deep-sky objects

Two interesting planetary nebulae lie in Aquila:

• NGC 6803 shows a small but bright ring
• NGC 6781 which bears some resemblance with the Owl Nebula in Ursa Major.

More deep-sky objects:

• NGC 6709: an open cluster of 6.7m
• NGC 6755: an open cluster of 7.5m
• NGC 6760: a globular cluster of 9.1m

History

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

Mythology

The constellation resembles a wide winged, soaring, short necked, bird, which the ancients identified as an eagle [1]. In classical Greek mythology, it was identified as the eagle which carried the thunderbolts of Zeus and was sent by him to carry the shepherd boy Ganymede he wanted to have with, represented by the neighbouring Aquarius, to Mount Olympus where he became the wine-pourer for all the gods. This explains why the largest moon of Jupiter was called Ganymede, Jupiter being the Roman name of Zeus.

This constellation was also known as Vultur volans to the Romans, not to be confused with Vultur cadens which was the Romans' name for what is now known as Lyra.

Aquila, together with other constellations in the Zodiac sign of Sagittarius (specifically, Lyra, Cygnus), may be a significant part of the origin of the myth of the Stymphalian Birds, one of The Twelve Labours of Herakles.

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