Aquila Constellation aka The Eagle
Aquila means “eagle” in Latin. In the earlier days, Ptolemy included it in his list of 48 Greek constellations. Now, the Aquila Constellation remains one of the 88 modern constellations that enchants our night sky. It was known as the giant bird of Zeus in Greek mythology (Roman: Jupiter). Some accounts say that it was the creation of Gaia.
The International Astronomical Union (IAU) ranks the Aquila Constellation as the 22nd largest modern constellation. Lying near the celestial equator, it occupies an area of 652 square degrees. Three of its stars are brighter than the third magnitude. Its brightest member, Altair, shines with an apparent magnitude of 0.76. It is part of an asterism called the Summer Triangle. Exoplanets were also discovered around some of Aquia’s stars.
The Milky Way passes within the borders of Aquila. Because of that, there are many interesting deep-sky objects in this constellation. It includes the Glowing Eye Nebula, the Phantom Streak Nebula, several star clusters, galaxies, and the Hercules-Corona Borealis Great Wall. Several meteor showers have their radiants in this constellation.
The celestial Eagle belongs to the Hercules family of constellations. It is a big family that has more than 15 constellations in it. The other members are:
What’s in a Name?
The constellation of Aquila has been related to birds across different cultures. To the Romans, they call it Vultur Volans or “the flying vulture.” Though we now know it as a Greek constellation, it may have been inspired by the Eagle constellation of the Babylonians.
What Does Aquila Look Like?
Aquila is enclosed in a 22-sided polygon. The pattern that we can form by connecting its star really looks like a bird with its wings spread. The line of its three brightest stars Alpha, Beta, and Gamma can be seen as the eagle’s head. Though, in some other versions, the three are part of the wings.
Where To See the Aquila Constellation
Aquila lies close to the celestial equator. It is in the fourth quadrant (NQ4) of the northern hemisphere. It is seen at locations between the latitudes +90° and −75°. Since it is more northerly in declination, it is not visible in some parts of the southern sky. Aquila’s celestial coordinates are:
- Right Ascension: 18h 41m – 20h 39m
- Declination: 18.69o – 11.87o
Aquila and Its Neighbors
Since Aquila is a large constellation, it is also bordered by many other neighbors. These surrounding constellations are Sagitta, Hercules, Ophiuchus, Serpens Cauda, Scutum, Sagittarius, Capricornus, Aquarius, and Delphinus. We can use these constellations as guides when looking for Aquila!
The Summer Triangle
Asterisms are just patterns we can form by connecting the stars from different constellations.
The Summer Triangle asterism is composed of stars that represent the three vertices of a triangle. One of them is Altair, from the Aquila constellation. The other two are Deneb from the constellation Cygnus and Vega from Lyra the lyre.
When To See the Aquila Constellation
Northern sky observers can spot Aquila in the night sky during summer. These months are June, July, and August. However, the best time to see it is during August nights at 9 pm. Around that time, the southern hemisphere is in the winter season.
Aquila and Its Stars
In the Almagest, Ptolemy included 19 stars in the Aquila constellation. Now, the constellation has 10 main stars. Three of them are brighter than the third magnitude.
More than five stars of Aquila were assigned permanent names. It includes Altair, Alshain, Tarazed, Okab, Libertas, Chechia, Phoenicia, and Petra.
Altair (α Aquilae)
Designated Alpha Aquilae, Altair is the brightest star in the constellation of the celestial eagle. We can easily spot it in the night sky because of its 0.76 apparent magnitude. It is the 12 brightest star overall. And with that, we don’t need to use any telescope as we can just see it with the naked eye.
Altair has an oblate shape. It is flattened in the polar areas because of its fast rotation rate. It is a main-sequence star with the stellar class of A7V. Compared to the Sun, Altair is more massive by about 1.8 times. Its radius is roughly twice that of the Sun, and it is 11 times more luminous. It is 17 light-years away from the solar system.
Names…and More Names
The IAU approved the name Altair for this star in 2016. But even before that, people from different cultures have given it different names. For instance, the Koori people called it Bunjil, while it was Poutu-te-rangi for the Māori people. Other names for this star in other cultures include Totyerguil, Mai-lapa, and Niú Láng Xīng, among others.
Aside from the Summer Triangle asterism, Altair is also part of other known star patterns. It forms a line with the stars β and γ Aquilae. The three of them are called the Family of Aquila (also Shaft of Aquila).
To the Arab observers, the three stars form the asterism which they called the “flying eagle/ vulture.” The Chinese people also have an asterism of the stars α, β, γ Aquilae. They called it Hé Gǔ or “the river drum.” In this sky pattern, the bright star Altair is called Hé Gǔ èr which means it is the second star of the river.
Alshain (β Aquilae)
Beta Aquilae is a multiple star system. It is composed of three stars with a combined apparent magnitude of about 3.87. The main component, β Aquilae A, was given the permanent name Alshain. Its companion star is in itself a spectroscopic binary.
Alshain is a yellow-hued star with the stellar classification of G8IV. It is 1.26 times more massive than the Sun, with a radius thrice the solar radius. This aging star radiates with the luminosity of more than three Suns combined. And though it is a G-type like our Sun, Alshain is already on its way to becoming a giant star.
In 2016, the IAU awarded the name Alshain to component A of this system. It was the traditional name of the system which means “the peregrine falcon.” This star is located 44.7 light-years from us.
Tarazed (γ Aquilae)
Tarazed is a solitary star with an orange hue. Its easily seen with the naked eye because it shines with an apparent magnitude of 2.712.
This star’s spectral class is K3 II. It is nearly four times as massive as the Sun. It is also much more luminous as it radiates 2,146 times the solar luminosity. At only 270 million years old, it is aging fast and is already in the bright giant stage.
Unlike the Sun that burns hydrogen into helium, Tarazed generates energy by converting helium into carbon. It will then become a white dwarf when it finally used up its helium fuel. It lies 395 light-years away from us.
Okab (ζ Aquilae)
Zeta Aquilae is a third-magnitude binary star system. The primary component, Zeta Aquilae A, is named Okab. It is a white-hued star with the stellar class A0 Vn. It is a main-sequence star just like the Sun. However, it has more than twice the Sun’s radius and is also more than twice as massive.
Okab’s companion is a much fainter star that is in the 12th magnitude. This system lies 83 light-years from the solar system.
Libertas (ξ Aquilae)
The star Xi Aquilae was given the official name Libertas in 2015. This red clump giant has an apparent magnitude of 4.722. At around 5 billion years old, this star is 16% more massive than the Sun.
Libertas is already an evolved star that generates energy by burning helium into carbon. An exoplanet was discovered around it, and it was named Fortitudo. This system is 183 light-years away from us.
Chechia (HD 192699)
Chechia is a G-type star with the spectral class G8 IV. This subgiant’s radius is more than four times that of the Sun. It is more massive by 26% and is even more luminous by 12,26 times. Its apparent magnitude is 6.45.
A planet was discovered orbiting this yellow-hued star in 2007. It was given the designation HD 192699 b and was later given the name Khomsa. This system is located 234 light-years away from Earth.
Phoenicia (HD 192263)
HD 192263, officially named Phoenicia, is an orange-hued star. Its spectral type is K2V. We cannot see it with the naked eye as its apparent magnitude is 7.79. As an orange dwarf, this star only has 65% of the Sun’s mass. It is also smaller and less luminous, radiating at only about 0.295 the solar luminosity.
A planet was discovered around it in 1999. It was designated HD 192263 b and was later given the name Beirut.
WASP-80 is an orange-hued star. It was officially named Petra in 2019. This K-type star is in the main sequence. It only has 61% of the Sun’s mass. We cannot see it with the naked eye as its apparent magnitude is only 11.93.
A hot Jupiter was discovered around this star in 2013. It was designated WASP-80 b and was given the name Wadirum. This system is 162 light-years away from us.
Eta Aquilae (η Aquilae)
Eta Aquilae is a multiple-star system with about 2-3 members. The combined apparent magnitude of the system is 3.87, so it is easily visible to the naked eye.
The primary component, η Aquilae A, is an F-type star that is a Cepheid variable. This supergiant star is around 6 times more massive than the Sun and is much more luminous. The secondary component is a B8.9 V class star. Another F-type companion was also resolved. The Eta Aquilae star system is around 1,400 light-years away.
15 Aquilae is also known as h Aquilae. It is a K-type star that has 14 times the solar radius. This giant star has a stellar class of K1 III. We can see it faintly with the naked eye as its apparent magnitude is 5.41. It is roughly 289 light-years away.
57 Aquilae is a binary star system. Both components are main-sequence stars with a blue-white hue. They form a wide binary. 57 Aql A has an apparent magnitude of 5.70 and is 480 light-years away. 57 Aql B, on the other hand, is a 6.48-magnitude star that is 510 light-years distant.
R Aquilae is a Mira variable star with an apparent magnitude that varies 5.3 to 12. It is a red giant that is already aging. Its spectral class is also changing between M5e and M9e. It is 780 light-years away.
FF Aquilae is a yellow-white supergiant star. As a Cepheid variable, it pulsates and changes in brightness. We can see it faintly with the naked eye as its apparent magnitude varies between 5.18 and 5.51. Its diameter also changes, as well as its temperature and luminosity. It is 1,350 light-years from us.
Planets in the Eagle’s Constellation
More than 15 stars in the constellation of Aquila were discovered to have planets. Below are some of them, as portrayed by NASA’s hypothetical visualization.
Fortitudo is the name approved by the IAU to Xi Aquilae b. This exoplanet orbits the K-type star Libertas. It is a gas giant that is as massive as 2.8 Jupiters. At a distance of 0.68 AU from the star, it completes an orbit in a period of 136.8 days.
Beirut is designated HD 192263 b. It is a gas giant with only 56% of Jupiter’s mass. It orbits the K-type star HD 192263 or Phoenicia in just about 24.4 days. This planetary system lies 64 light-years from the Earth.
Khomsa is another gas giant that is around one of the stars of Aquila. Also called HD 192699 b, it is 1.063 AU from the star Chechia. It is more than twice as massive as Jupiter. It takes this exoplanet 340.9 days to orbit its star.
Wadirum, or WASP-80 b, is a giant exoplanet that orbits the star named Petra. Its radius is nearly the same as Jupiter, but it is only half as massive. It is a fast-moving planet as its orbital period is only 3.1 days.
HD 183263 b
HD 183263 b is another gas giant that is nearly four times as massive as Jupiter. It orbits a yellow-hued star in 1.7 years. It was discovered in 2004 through the radial velocity method.
COROT-8 b is a gas giant located 1,050 light-years away from us. It only has 22% of Jupiter’s mass. This exoplanet follows a circular orbit around a K-type star. It is 0.063 AU from the star and completes a journey around it every 6 days.
Deep-Sky Objects in Aquila Constellation
The constellation of Aquila is a rich field of deep-sky objects, though it has no Messier objects. It contains unique-looking nebulae, dark nebulae, star clusters, and the extragalactic object called the Hercules-Corona Borealis Great Wall.
Glowing Eye Nebula
The Glowing Eye Nebula is designated NGC 7651 in the New General Catalog. It is also called the Dandelion Puffball Nebula because of its unique appearance. It has an inner bubble that is surrounded by two halos.
NGC 7651 is a planetary nebula that is about 0.8 light-years across. Its central star is a Wolf Rayet star that is losing mass. This deep-sky object is 6,500 light-years away from us.
Phantom Streak Nebula
The Phantom Streak Nebula is better known as NGC 6741. It is a planetary nebula with an apparent magnitude of 11. We cannot see it with the naked eye. It was discovered by Edward Charles Pickering in 1882. This deep-sky object is about 7000 light-years distant.
Barnard’s E Nebula
Barnard’s E Nebula is named after Edwards Emerson Barnard. He observed and cataloged a lot of dark nebulae. These dark deep-sky objects are made of dust. Some examples include B142, B143, B334, B336, B337, and B340.
The “E” Nebula or Barnard’s E Nebula is composed of B142 and B143. The dark field of these two nebulae forms a letter “E” against the background of stars of the Milky Way. The diameter of this dark “E” is estimated to be the same size as that of 2 full moons. This pair lies around 2,000 light-years away.
NGC 6778 is another planetary nebula in the constellation of the celestial eagle. This nebula has an irregular shell that seems to project some jet-like structures. At the heart of this planetary nebula is a binary star that is close to each other. It is 10,300 light-years away from the solar system.
IRAS 19024+0044 is a unique-looking protoplanetary nebula. It is only short-lived as it happens only during a star’s evolution from the giant branch into the nebula phase.
NGC 6781 is a deep-sky object found in the equatorial constellation of Aquila the Eagle. It is one of the many planetary nebulae in the constellation.
NGC 6760 is yet another type of deep-sky object. It is a globular cluster that is about 24,100 light-years away from the solar system.
NGC 6755 is an open cluster with an apparent magnitude of 7.5. It is located west of the binary star system of Delta Aquilae. This cluster is 15′ as seen on Earth, and is 4,632 light-years away from the Sun.
NGC 6709 is another open cluster in the Aquila constellation. Its apparent magnitude is 6.7. We can find this deep-sky object five degrees southwest of the star Zeta Aquilae. It is roughly 3,504 light-years from the Sun.
Meteor Showers Related to Aquila
The meteor showers June Aquilids and Epsilon Aquilids are related to Aquila. Their radiants or point of origin seem to be from the eagle constellation. However, these showers are not that bright. You would need some optical instruments to see these light shows.
The Epsilon Aquilids meteor shower occurs around May 4-27 every year. The best time to view it would be on May 17th as it is when it has its peak activity.
Mythology Related to Aquila Constellation
Eagles are mighty creatures that often represent greatness. These birds were already seen as important creatures even in antiquity. Also, they are often related to the sky gods of Greek and Roman mythology.
The Eagle of Zeus
The chief god of the Olympians, Zeus, sometimes transforms into an eagle. Because of that, this bird is one of his many symbols. It was also believed that eagles are divine birds. People in the past looked up to them because these birds were thought to be oracles that talked to the gods.
The eagle was considered the messenger of Zeus and the carrier of his famous thunderbolt. In another story, Zeus sent this bird to bring Ganymede to Mount Olympus. The young shepherd later became the cupbearer of the gods. And because of that, he was associated with the Aquarius constellation.
The Eagle of Zeus/Jupiter is called Aetos Dios in Roman mythology. It was used as a symbol of many Roman emperors and legions as a whole. In other versions, it was said that the principal goddess Gaia created the eagle.
Periphas Was Turned Into an Eagle
There was a king named Periphas who was loved by his people. They adored and honored him like the god Zeus. However, Zeus was not so happy about it. He did not like that the mortal king was treated like him.
Zeus planned to punish Periphas and destroy his family. The mortal king was spared when Apollo intervened but Zeus still wanted revenge. Instead of killing Periphas, he turned the king into an eagle. This bird became the guard of Zeus’s scepter.
Extra: Claudius Ptolemaeus and the Almagest
The constellations as we know them today are a product of collective efforts made by different people throughout time. One of the most influential scientific texts of all time is the Almagest.
The Almagest was a work originally written in the Greek language around the 2nd century. It was the work of Claudius Ptolemaeus. He was better known as Ptolemy. This text contained mathematical and astronomical observations that would later become very useful to the study of the stars and other celestial objects. It also included data about their apparent motions.
The Almagest was a work in progress for a long time. Many believed that it was completed about a quarter-century after Ptolemy began his observations. That is about 25 years!
It had different names:
- Mathēmatikē Syntaxis (ancient Greek; original title)
- Syntaxis Mathematica (Latin)
- al-majisṭī (Arabic)
The one that stuck was its Arabic name, hence the name Almagest in English. The Arabic translation was the basis of the famous Latin translation in the 12th century called Almagestum.
The original Greek work, Syntaxis Mathematica, was made up of thirteen sections, called books.
|The Thirteen Books of Syntaxis Mathematica|
|Book I||Cosmology of Aristotle|
|Book II||The daily motion of the heavens|
|Book III||Length of the year and Sun’s motion|
|Book IV||The motion of the Moon as well as the sizes
and distances of the Sun and Moon relative to the Earth
|Book VI||Solar and Lunar eclipses|
|Book VII||Motions of fixed stars and a star catalog
of 1022 stars (they are described by their positions in the constellations in longitude and latitude.
|Book IX||About the five naked-eye planets (Mercury, Venus, Mars, Jupiter, and Saturn)|
|Book X||Motions of Venus and Mars|
|Book XI||Motions of Jupiter and Saturn|
|Book XII||About stations and retrograde motion|
|Book XIII||Motions in latitude (deviation of planets from the Sun’s path)|
In Book VII and VIII, Ptolemy listed 48 constellations. Twelve of these are zodiacs, 21 are constellations to the north of the zodiac, and 15 to its south. The Aquila constellation was included in this early work.
It is fascinating to know that a lot of what we know about the constellations now were discovered way back in the 2nd century. But even though a lot of facts from the Almagest were retained, some were not. The geocentric belief is one of them.
Ptolemy’s Cosmos (Geocentric vs Heliocentric Views)
One of the main points of the Almagest revolves around the fact at the time that the Earth is the center of the cosmos. It was also the belief of Aristotle, the grandfather of science.
Below is a representation of Ptolemy’s model following the geocentric belief, or that the Earth is the center of the universe.
The geocentric view remained for a long time partly because of the influence of Aristotle. It was until the time of Nicolaus Copernicus that this was proven wrong. Copernicus believed in the heliocentric view, or that the Sun is the center of the universe. Many did not accept this view.
It was until 100 years after that Galileo Galilei conducted studies to support this view. He got in a lot of trouble for this. But because of his efforts, other scientists like Sir Isaac Newton and Johannes Kepler have studied this as well. Our understanding of the universe has become what it is today thanks to them!
Aquila and neighbors: https://in-the-sky.org/images/constellations/con_AQL_000.png
Summer Triangle: https://upload.wikimedia.org/wikipedia/commons/5/5e/Summer_triangle_map.png
α,β, and γ Aquilae: https://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Altair%2C_Tarazed_and_Alshain.jpg/1200px-Altair%2C_Tarazed_and_Alshain.jpg
Glowing Eye Nebula: https://upload.wikimedia.org/wikipedia/commons/c/c0/NGC6751.jpg
Phantom Streak Nebula:
NGC 6778: https://junior-ccd.fn-f.de/NGC6778.jpg
Barnard’s E Nebula: http://cs.astronomy.com/resized-image.ashx/__size/1000×0/__key/telligent-evolution-components-attachments/13-59-00-00-00-42-46-56/dso_2D00_nebulae_2D00_b143.jpg
NGC 6781: https://upload.wikimedia.org/wikipedia/commons/thumb/6/69/NGC-6781.jpg/1024px-NGC-6781.jpg
NGC 6760: https://nineplanets.org/wp-content/uploads/2020/08/ngc6760_LRGBcrop.jpg
IRAS 19024+0044: https://upload.wikimedia.org/wikipedia/commons/a/aa/IRAS_19024%2B0044.jpg
NGC 6755: https://upload.wikimedia.org/wikipedia/commons/5/51/NGC_6755.png
NGC 6709: https://upload.wikimedia.org/wikipedia/commons/8/8d/NGC_6709_large.png
Meteor Showers: https://i.pinimg.com/originals/62/b8/ed/62b8edb8241b5ba8041fbefd0e8bc958.gif
The Eagle of Zeus: https://www.theoi.com/image/K1.1Zeus.jpg
The Eagle and Ganymede: https://constellationsofwords.com/images/Ganymede.jpg
Periphas Was Turned Into an Eagle: https://www.figuren-shop.de/media/image/7a/39/3c/Zeus-Figur-1_1280x1280.jpg
Geocentric belief: https://upload.wikimedia.org/wikipedia/commons/thumb/3/3a/Ptolemaicsystem-small.png/330px-Ptolemaicsystem-small.png)
Galileo Galilei: https://upload.wikimedia.org/wikipedia/commons/9/94/Galileo_Galilei_2.jpg