Constellations Codexery

Aquila

A constellation representing an eagle, home to Altair and many novae.

Aquila

Aquila is a constellation that sits on the celestial equator. Its Latin name means "eagle," and its mythological meaning is debated: some traditions say it represents the eagle that carried Zeus's (or Jupiter's) thunderbolts in Greco-Roman myth, while others identify it as the bird Zeus sent to attack Prometheus. The constellation's brightest star, Altair, forms one corner of the Summer Triangle asterism. Because Aquila lies along the Milky Way, it is best viewed during the northern summer. This location means the constellation contains many star clusters and nebulae, though these objects are faint, and there are few galaxies within its borders.

The constellation was one of the 48 described by the second-century astronomer Ptolemy, though it had already been mentioned by Eudoxus in the fourth century BC and Aratus in the third century BC. Today, it is one of the 88 constellations officially recognized by the International Astronomical Union. The Romans also knew it as Vultur volans (the flying vulture), not to be confused with Vultur cadens, their name for Lyra. In Greco-Roman mythology, Aquila is often taken to be the eagle that carried Zeus's thunderbolts. It is also linked to the eagle that kidnapped Ganymede, a Trojan prince (associated with Aquarius), and brought him to Mount Olympus to serve as the gods' cup-bearer.

Ptolemy catalogued 19 stars jointly in Aquila and in the now-obsolete constellation Antinous, which was named during the reign of Emperor Hadrian (AD 117–138). This grouping is sometimes mistakenly attributed to Tycho Brahe, who catalogued 12 stars in Aquila and seven in Antinous. Later, Hevelius determined 23 stars in Aquila and 19 in Antinous. The Greek Aquila likely derives from the Babylonian constellation of the Eagle, though it is occasionally misidentified as a seagull in the same area of the sky.

Because Aquila lies in the Milky Way, it contains rich starfields and has been the site of many novae. Its brightest star, Altair (α Aql), is one of the closest naked-eye stars to Earth, at a distance of 17 light-years. Its name comes from the Arabic phrase *al-nasr al-tair*, meaning "the flying eagle." Altair has a magnitude of 0.76 and is an A-type main-sequence star with 1.8 times the Sun's mass and 11 times its luminosity. It rotates quickly, giving it an oblate shape flattened at the poles. β Aql (Alshain) is a yellow-hued star of magnitude 3.7, 45 light-years away. Its name comes from the Arabic *shahin-i tarazu*, meaning "the balance," a term that originally referred to Altair, Alshain, and Tarazed together. The primary is a G-type subgiant (spectral type G9.5 IV) with three times the Sun's radius and six times its luminosity, and its companion is a red dwarf. γ Aql (Tarazed) is an orange-hued giant of about magnitude 2.7, 460 light-years away. Its name, like Alshain's, comes from the Arabic for "the balance." It is the second-brightest star in the constellation and an unconfirmed variable. ζ Aql (Okab) is a binary star of magnitude 3.0, 83 light-years away, with an A-type main-sequence primary and a secondary half the Sun's mass. θ Aql was given the proper name Antinous on 6 June 2024. δ Aql was named Guqi on 18 June 2026. η Aql (Pagru, since 18 June 2026) is a yellow-white supergiant 1200 light-years away, one of the brightest Cepheid variables, with a magnitude range of 3.5 to 4.4 over 7.2 days. Its variability was first noted by Edward Pigott in 1784. It has two companion stars: a B-type main-sequence star and an F-type main-sequence star. ε Aql was named Arin-majlep on 18 June 2026. ξ Aql was named Libertas on 15 December 2015. 15 Aql is an optical double: an orange-hued giant of magnitude 5.41 (spectral type K1 III, 325 light-years away) and a purple-hued star of magnitude 7.0 (550 light-years away), easily resolved in small telescopes. σ Aql was named Hru on 18 June 2026. τ Aql was named Tianfu on 16 May 2024. 57 Aql is a binary with a blue-hued primary (magnitude 5.7) and a white secondary (magnitude 6.5), about 350 light-years away, both rotating rapidly and easily resolved in small telescopes. R Aql is a red-hued giant 690 light-years away, a Mira variable with a magnitude range of 6.0 to 12.0 over about 9 months, and a diameter of 400 times the Sun's. V Aql is a typical cool carbon star, one of the reddest examples of its kind, observable through common amateur telescopes. FF Aql is a yellow-white supergiant 2500 light-years away, a Cepheid variable with a magnitude range of 5.2 to 5.7 over 4.5 days. It is a spectroscopic binary (spectral type F6Ib) with a third star also in the system, plus a fourth star probably unrelated.

One former star, ρ Aql, an A-type star with lower metallicity than the Sun, moved across the border into neighboring Delphinus in 1992.

A bright nova was observed in Aquila in 1918 (Nova Aquilae 1918), briefly shining brighter than Altair. First seen by Zygmunt Laskowski and confirmed on the night of 8 June 1918, it reached a peak apparent magnitude of −0.5, making it the brightest nova recorded since the invention of the telescope.

Three interesting planetary nebulae lie within Aquila.

First cataloged by
Ptolemy (2nd century)
Earlier mentions
Eudoxus (4th century BC) and Aratus (3rd century BC)
Number of stars cataloged by Ptolemy
19 (jointly with Antinous)
Brightest star
Altair (α Aql), magnitude 0.76
Distance of Altair
17 light-years
Modern constellation count
88 (defined by IAU)

Lore & Background

Aquila was one of the 48 constellations described by the second-century astronomer Ptolemy. It had been earlier mentioned by Eudoxus in the fourth century BC and Aratus in the third 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. It is often held to represent the eagle which held Zeus's/Jupiter's thunderbolts in Greco-Roman mythology. Aquila is also associated with the eagle that kidnapped Ganymede, a son of one of the kings of Troy (associated with Aquarius), to Mount Olympus to serve as cup-bearer to the gods. Hevelius determined 23 stars in the first and 19 in the second. The Greek Aquila is probably based on the Babylonian constellation of the Eagle, but is sometimes mistakenly thought as a seagull which is located in the same area as the Greek constellation.

Reader's Guide

Aquila is significant as one of the 48 constellations cataloged by Ptolemy and remains one of the 88 modern constellations defined by the IAU. Its brightest star, Altair, is a prominent vertex of the Summer Triangle asterism and one of the closest naked-eye stars to Earth at 17 light-years. It also holds the Hercules–Corona Borealis Great Wall, possibly the largest single mass concentration of galaxies in the Universe. The constellation's mythology is mixed, representing either the eagle that carried Zeus's thunderbolts or the one that attacked Prometheus, and it is also linked to the abduction of Ganymede. NASA's Pioneer 11 space probe is expected to pass near Lambda Aquilae in about 4 million years.

Did You Know?

Mythology & Naming

Aquila's identity in the night sky has never been entirely settled. The Latin name simply means "eagle," but which eagle depends on which storyteller you ask. One tradition casts it as the loyal bird that carried Zeus's thunderbolts across the Greek and Roman heavens. Another makes it the instrument of divine punishment, the eagle Zeus dispatched to torment Prometheus. A third thread ties it to the dramatic abduction of Ganymede, a Trojan prince who was snatched up to Olympus to pour wine for the gods — a story that links Aquila to Aquarius, the water-bearer. The Romans had their own label, Vultur volans, meaning "the flying vulture," a name they carefully distinguished from Vultur cadens, their term for Lyra. Scholars also note that the Greek eagle likely descends from a Babylonian constellation of the same bird, though it is sometimes confused with a seagull figure that occupied the same patch of sky. These layered narratives give Aquila a rich, contested mythology that has persisted for over two millennia.

Stellar Highlights

Altair, the constellation's brightest star, sits just 17 light-years from Earth and anchors the famous Summer Triangle alongside Vega and Deneb. Its Arabic name, al-nasr al-tair, translates to "the flying eagle," a fitting nod to the constellation's identity. At magnitude 0.76, it is an A-type main-sequence star with 1.8 solar masses and 11 times the Sun's luminosity; its rapid rotation flattens it into an oblate shape at the poles. Further out, the Cepheid supergiant Pagru pulses between magnitudes 3.5 and 4.4 over 7.2 days, while the Mira variable R Aql swells to a staggering 400 solar diameters and dims to magnitude 12 over roughly nine months. The constellation also hosts the Cool Carbon Star V Aql, one of the reddest examples of its class visible to amateur observers.

Deep-Sky Objects & Eruptive Events

Because Aquila lies directly along the Milky Way, its borders are threaded with rich starfields, open clusters, and planetary nebulae, though galaxies are scarce. Aquila has also been a stage for dramatic stellar explosions. The constellation's position in the galactic plane makes it a natural hunting ground for such transient and deep-sky phenomena.

Historical Cataloguing & Modern Identity

Aquila has been formally recognized for over two thousand years. Eudoxus mentioned it in the fourth century BC, Aratus followed in the third, and Ptolemy included it among his 48 constellations in the second century AD. Hevelius later counted 23 stars in Aquila and 19 in Antinous. In the modern era, the International Astronomical Union enshrined Aquila among its 88 official constellations. The constellation sits on the celestial equator and is best observed during northern summer evenings when it arcs high overhead along the Milky Way. Its long cataloguing history, from Babylonian roots through Greek, Roman, and modern astronomical traditions, makes it one of the most continuously tracked regions of the sky in human history.

Common Misconceptions (Editorial)

Some people mistakenly believe Aquila solely represents the eagle that carried Zeus’s thunderbolts, but the facts show its representation is mixed, with other traditions associating it with the eagle that attacked Prometheus or the one that kidnapped Ganymede. Another common error is thinking Aquila was named after the Latin word for “eagle” without any alternate Roman name, but it was also known as Vultur volans (the flying vulture). Additionally, it is sometimes incorrectly assumed that the constellation was created in modern times, whereas it was one of the 48 constellations described by Ptolemy in the second century and was mentioned even earlier by Eudoxus and Aratus.

Why It Matters (Editorial)

Aquila endures because it occupies a prominent spot along the Milky Way and anchors the famous Summer Triangle with its bright star Altair, making it a reliable marker for skywatchers across millennia. Its layered mythology—spanning Greek, Roman, and Babylonian roots—reflects how ancient cultures used the stars to tell stories about power, punishment, and transformation, reminding us that constellations are both scientific coordinates and cultural keepsakes.

Frequently Asked Questions

Who is Aquila?

Aquila is one of the 88 IAU-defined constellations, depicting an eagle. In Greek-Roman tradition it is linked to Zeus (Jupiter), either as the bird that carried his thunderbolts or as the one he sent to torment Prometheus. It was first formally cataloged by Ptolemy in the 2nd century, though Eudoxus and Aratus referenced it earlier.

What is Altair and why does it matter?

Altair (α Aql) is Aquila's brightest star, shining at magnitude 0.76 from a distance of only 17 light-years. It anchors one vertex of the Summer Triangle asterism alongside Vega and Deneb, making it one of the most instantly recognizable points in the northern summer sky.

When and where is the best time to see Aquila?

Because it sits right on the celestial equator and runs along the Milky Way, Aquila is most prominent in the northern summer months. From mid-northern latitudes it climbs high after sunset, placing it squarely within the bright galactic band.

What is the mythology behind Aquila?

Two competing Greek stories are attached to the eagle: one casts it as Zeus's personal courier for his lightning bolts, while the other identifies it as the bird he unleashed to peck at Prometheus's liver as eternal punishment. Both versions survive in classical sources, so the eagle's 'true' role remains a matter of interpretive debate.

What can I find in Aquila besides stars?

The constellation contains several open clusters and faint nebulae embedded in the Milky Way, though none are particularly bright to the naked eye. It has also been the site of multiple recorded novae, making it a popular target for variable-star observers.

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