AQUILA  "The Eagle"  pronounced ACK-will-ah

Chart showing the constellations.

This constellation dates from ancient times, represents the bird that in Mythology was the companion of Jupiter, and often carried his thunderbolts.  Ptolemy assigned nine stars to it, but the six southerly stars which he placed in the obsolete Antinous are now included in it. Aquila lies in the Milky Way and contains rich star fields, particularly towards the neighbouring constellation Scutum.  Aquila straddles the celestial equator in the winter Milky Way and is easily recognised by the bright white star Altair with its two flanking yellow stars β Aql and γ Aql the former being the less bright. 

Aquila contains the unusual object SS 433.  This is a unique binary star system lying in the centre of a supernova remnant.  The stars cannot be resolved apart visually, but spectroscopes on large telescopes reveal emission lines that are both red and blue shifted, showing jets emerging from the star with a velocity about one quarter the sped of light both towards and away from us.  These jets precess, and thus seem to sweep around the sky with a period of about 164 days.  The object is an eclipsing binary star with a period of 6.4 days, containing a very hot star with an invisible companion, that is probably a neutron star because of the bizarre relativistic effects.

To find Aquila look north in the late evening sky, and find the bright star Altair.  From the more northerly regions of New Zealand Altair is the apex of the "Summer Triangle"  (Northern hemisphere) with Vega in Lyra and Deneb in Cygnus being at the base.

Chart showing Aquila as seen towards the north in mid evening during September.

Aquila chart

Constellatio Ophiuchus Constellatio Serpens Constellation Scutum Constellation Sagittarius Constellation Capricornus Constellation Aquarius Constellation Delphinus Constellation Equuleus Constellation Cygnus Constellation Sagitta Constellation Hercules

Some stars and interesting objects in the Constellations

α Aquilae (Altair, pronounced ell-TAH-eer, an Arabic name meaning flying eagle), is a 0.77 magnitude white star 16 light years away, among the Sun's closest neighbours.

β Aql (Alshain) is a magnitude 3.7 yellow star 42 light years away.

γ Aql (Tarazed), is a magnitude 2.7 yellow giant star 280 light years away.

η Aql is 1400 light years away.  It is one of the brightest Cepheid variable stars, ranging in brightness from magnitude 4.1 to magnitude 5.3 every 7.2 days.

15 Aql is a magnitude 5.4 yellow giant star 390 light years away, with a purplish magnitude 7.2 companion star easily visible in small telescopes.

57 Aql is an easy double star system for small telescopes, consisting of a bluish magnitude 5.7 star with a 6.5 magnitude companion.  They lie about 590 light years away.

NGC 6709 is a loosely scattered cluster of medium bright stars lying in a fine field.  This fairly rich cluster is not effective with small apertures.

NGC 6781 is a large moderately bright grey planetary nebula.  An OIII filter improves the telescopic view and allows the annular character of the nebula to be seen.

Visibility

Aquila lies on the celestial equator and is visible to the north in the evening during September. The brightest star, Altair is due north about 9.30 pm (NZST) on September 1, 8.30 on September 15 and 7.30 on September 30. It has an altitude just below 40° from the South Island and a little over 40° from the north of the North Island of New Zealand.

In August look for Aquila to the north-east mid evening. July sees the constellation low between north-east and east at the same time.
By the end of October, Altair will be rather lower to the north-west once it gets dark. By the end of November it will be getting lost in the evening twilight low, a little north of west.