Aquila constellation is located in the northern sky, near the celestial equator. The constellation’s name means “the eagle” in Latin.
The constellation represents the eagle of the Roman god Jupiter in mythology. It was first catalogued by the Greek astronomer Ptolemy in the 2nd century.
Aquila is home to two very famous stars, Altair and Tarazed, as well as to several interesting deep sky objects: the planetary nebulae NGC 6803, NGC 6804, NGC 6781 and the Phantom Streak Nebula (NGC 6741), the open clusters NGC 6709 and NGC 6755, and the dark nebula B143-4.
FACTS, LOCATION & MAP
Aquila is the 22nd biggest star constellation in the sky, occupying an area of 652 square degrees in the fourth quadrant of the northern hemisphere (NQ4). It can be seen at latitudes between +90° and -75°. The neighboring constellations are Aquarius, Capricornus, Delphinus, Hercules, Ophiuchus, Sagitta, Sagittarius, Scutum, and Serpens Cauda.
Aquila has seven stars with known planets and contains no Messier objects. The brightest star in the constellation is Altair, Alpha Aquilae, which is also the 12th brightest star in the sky. There are two meteor showers associated with Aquila: the June Aquilids and the Epsilon Aquilids.
Aquila belongs to the Hercules family of constellations, together with Ara, Centaurus, Corona Australis, Corvus, Crater, Crux, Cygnus, Hercules, Hydra, Lupus, Lyra, Ophiuchus, Sagitta, Scutum, Serpens, Sextans, Triangulum Australe, and Vulpecula.
In Greek mythology, Aquila is identified as the eagle that carried Zeus’ thunderbolts and was once dispatched by the god to carry Ganymede, the young Trojan boy Zeus desired, to Olympus to be the cup bearer of the gods. Ganymede is represented by the neighbouring constellation Aquarius.
In another story, the eagle is found guarding the arrow of Eros (represented by the constellation Sagitta), which hit Zeus and made him love-struck.
In yet another myth, Aquila represents Aphrodite disguised as an eagle, pretending to pursue Zeus in the form of a swan, so that Zeus’ love interest, the goddess Nemesis, would give him shelter. In the story, Zeus later placed the images of the eagle and the swan among the stars to commemorate the event.
The name of the brightest star in the constellation, Altair, is derived from the Arabic al-nasr al-ta’ir, which means “flying eagle” or “vulture.” Ptolemy called the star Aetus, which is Latin for “eagle.” Similarly, both Babylonians and Sumerians called Altair “the eagle star.”
MAJOR STARS IN AQUILA
Altair – α Aquilae (Alpha Aquilae)
Altair is the 12th brightest star in the sky, with an apparent magnitude of 0.77. It is an A-type main sequence star (hydrogen fusing dwarf) that has three visual companions. Lying only 16.8 light-years away, Altair is one of the closest stars to Earth that is visible to the naked eye. The star’s name is derived from the Arabic phrase an-nasr at-ta’ir, which means “the flying eagle.”
Altair has 1.8 times the mass of the Sun. Because it rotates very rapidly (286 km/s at the equator), Altair’s shape is not spherical, but flattened at the poles. The star also moves across the sky relatively quickly. It shifts by about a degree in 5000 years.
Altair is one of the three stars that form the Summer Triangle, an asterism that can be seen directly overhead at mid-northern latitudes in the summer. Altair is the southern star in the triangle. The other two stars that form the asterism are Deneb (Alpha Cygni) in the constellation Cygnus and Vega (Alpha Lyrae) in Lyra.
Alshain – β Aquilae (Beta Aquilae)
Alshain is only the seventh brightest star in Aquila, but was designated Beta Aquilae nonetheless by Johann Bayer. It is a class G subgiant approximately 44.7 light years distant.
The name Alshain is derived from the Perso-Arabic aš-šāhīn, which means “the (peregrine) falcon.” The star has a 12th magnitude visual companion, Beta Aquilae B, a class M red dwarf, lying 13 arc seconds away. Alshain is six times more luminous than the Sun and slightly variable in luminosity. It has an apparent magnitude of 3.71.
Tarazed – γ Aquilae (Gamma Aquilae)
Tarazed is the second brightest star in Aquila. Its name is derived from the Persian phrase šāhin tarāzu, which means “the beam of the scale.” It is a class K (spectral class K3) bright giant with an apparent magnitude of 2.72, approximately 461 light years distant.
Tarazed is 2960 times more luminous than the Sun and has a radius of 110 solar, taking up about half an AU in the sky. It is a known source of X-rays. Tarazed is about 100 million years old and yet it is already burning helium into carbon in its core.
Deneb el Okab – ε Aquilae (Epsilon Aquilae)
Epsilon Aquilae, or Deneb el Okab, is a triple star system about 154 light years distant. Its name is derived from the Arabic phrase ðanab al-cuqāb, which means “the tail of the eagle.” The brightest component of Epsilon Aquilae is an orange K-type giant which is a known barium star; one containing a lot of barium and other heavy elements. Epsilon Aquilae has an apparent magnitude of 4.02. The companions, suspected optical binaries, are 10th magnitude stars.
To differentiate Epsilon from Zeta Aquilae, which is also called Deneb el Okab, Epsilon Aquilae is often referred to as Deneb el Okab Borealis, because it is located north of Zeta Aquilae, which is subsequently referred to as Deneb el Okab Australis.
Deneb el Okab – ζ Aquilae (Zeta Aquilae)
Zeta Aquilae is another triple star system, approximately 83.2 light years distant, with a white A-type main sequence dwarf for a primary. The main star has an apparent magnitude of 2.99, while the companions are 12th magnitude stars.
Bezek – η Aquilae (Eta Aquilae)
Eta Aquilae is a yellow-white supergiant, approximately 1200 light years from Earth. It is a Cepheid variable star, with its apparent magnitude varying between 3.5 and 4.4 with a period of 7.176641 days. Eta Aquilae is one of the easiest Cepheids to distinguish by the naked eye. The star is 3000 times more luminous than the Sun. The name Bezek comes from the Hebrew word bazak, which means “lightning.”
Other notable stars:
Tseen Foo – θ Aquilae (Theta Aquilae)
Theta Aquilae is a spectroscopic binary star, about 287 light years distant. The name Tseen Foo is derived from the Mandarin word tianfu, which means “the heavenly rafter” and also “drumsticks.” The Chinese call the asterism the star forms together with 62 Aquilae, 58 Aquilae and Eta Aquilae the Celestial Drumsticks. Tseen Foo is a clue-white B-type giant with an apparent magnitude of 3.24.
Al Thalimain – ι Aquilae (Iota Aquilae)
Iota Aquilae is a blue-white B-type star approximately 307 light years distant. The name Al Thalimain, which the star shares with Lambda Aquilae, means “the two ostriches” in Arabic. Iota Aquilae has an apparent magnitude of 4.36.
Al Thalimain – λ Aquilae (Lambda Aquilae)
Lambda Aquilae, a blue-white B-type main sequence dwarf, is sometimes called Al Thalimain Prior, to differentiate it from Iota Aquilae. The star has an apparent magnitude of 3.43 and is 125 light years distant.
In 1973, NASA launched the probe Pioneer 11 that will presumably approach Lambda Aquilae in about four million years (if all goes well). The probe left the solar system in 1990 and, because its power was too weak, it has not transmitted any data since 1995.
15 Aquilae is a magnitude 5 orange giant that has a faint optical companion, HD 177442. The star is approximately 289 light years distant and easy to observe in small telescopes.
Tso Ke – ρ Aquilae (Rho Aquilae)
Rho Aquilae is a white A-type main sequence dwarf, approximately 154 light years distant. It has an apparent magnitude of 4.94. The star’s traditional name, Tso Ke, comes from Mandarin and means “the left flag.” The star no longer belongs to the constellation Aquila, as it crossed the border into Delphinus in 1992.
DEEP SKY OBJECTS IN AQUILA
Phantom Streak Nebula – NGC 6741
NGC 6741 is a planetary nebula first discovered in 1882 by the American astronomer Edward Charles Pickering. The nebula is approximately 7000 light years distant. Even though it is classified as a planetary nebula, there are no planets responsible for its formation. It merely resembled the outer giant planets in our solar system when it was first spotted.
NGC 6709 is an open star cluster that can be easily resolved in a small telescope. It lies five degrees southwest of Zeta Aquilae. The stars are loosely arranged into a diamond-like shape.
NGC 6755 is another open cluster. The brightest stars are of 12th and 13th magnitude. The cluster is located 4.5 degrees west of Delta Aquilae.
B143-4 is a dark nebula spanning more than a degree in size, located 1.5 degrees west of Gamma Aquilae.
Other notable deep sky objects:
NGC 6803 is a planetary nebula shaped like a ring.
NGC 6804 is a planetary nebula that appears as a small, bright ring.
NGC 6891 is another planetary nebula
NGC 6751, also known as the Glowing Eye, is another planetary nebula.
NGC 6760 is a globular cluster.
NGC 6749 is an open cluster.
NGC 6778 is a planetary nebula.
NGC 6772 is also a planetary nebula.