Ara Constellation aka The Altar
Ara is a southern constellation. The name has a Latin origin which means “the Altar.” Claudius Ptolemy included it in the 2nd-century Almagest and it is one of the southernmost constellations that he catalogued.
It is one of the smallest constellations in the night sky, occupying an area of 237.1 square degrees. That is just 0.575% of our entire sky. In terms of size, it sits in the 63rd rank among the 88 modern constellations recognized by the International Astronomical Union (IAU). The largest of which is Hydra, covering 1,303 square degrees.
Three-letter abbreviations are used for every constellation as adopted by the IAU. Since the Ara constellation has a short name, the same name, Ara, is used as its abbreviation. The genitive is Arae.
Some notable stars are in this small constellation because it is located close to the Milky Way. Its brightest stars, Beta and Alpha Arae, are brighter than the third magnitude. Also, seven of its stars have exoplanets. While no meteor showers have their radiant from the Ara constellation, it has an array of deep-sky objects.
Ancient Greeks have connected this constellation to their mythology. There are two main stories related to it. One is about the great war between the Greek gods and the Titans. The other is that of King Lycaon of Arcadia. Some other stories related to it involve the nearby constellations of Lupus and Centaurus.
Ara is a member of the Hercules family of constellations, the biggest group among the eight. Other members are:
- Hercules (the Kneeler)
- Ophiuchus (the Serpent Bearer)
- Ara (the Celestial Alter)
- Serpens (the Serpent)
- Sextans (the Sextant)
- Crater (the Cup)
- Corvus (the Crow)
- Hydra (the Female Water Snake)
- Centaurus (the Centaur)
- Crux (the Southern Cross)
- Lupus (the Wolf)
- Triangulum Australe (the Southern Triangle)
- Corona Australis (the Southern Crown)
- Aquila (the Eagle)
- Sagitta (the Arrow)
- Vulpecula (the Fox)
- Cygnus (the Swan)
- Lyra (the Lyre)
What’s In A Name?
The altar constellation had been known by different names throughout ages before it became Ara. It was known to many as an altar with incense burning on top. It was called Tul-Ku by the Greeks, which means “Holy Altar.”
The Arabs related the constellation to the Greeks’ interpretation and called it Al Mijmarah, which translated to “The Censer.” For the Romans, it was known by the name Thymele, the small altar of Dionysus in the center of the Greek theater. Another name association is Ara Centauri, meaning “Centaur’s Altar.” This name was around the time when the constellations of Ara, Centaurus, and Lupus were taken as one.
What Does Ara Look Like?
The boundaries of Ara the Altar is defined by a 12-sided polygon set in 1930 by Eugène Delporte. Its pattern has a distinct “H” shape. Other versions of the constellation outline is a variation of it.
It is often portrayed in illustrations as an altar whose smoke is flaming southward, like the one in Johann Elert Bode’s Uranographia.
Where To See the Ara Constellation
Ara the Altar is located in the third quadrant of the southern sky (SQ3). It has the coordinates 17 hours right ascension and 55° south declination in the celestial sphere. From observers here on Earth, it can be seen between the latitudes +25° and -90°. The whole constellation of Ara can be seen by observers whose locations are south of 22° north.
Ara and Its Neighbors
Ara is often depicted as an upside-down altar. It is surrounded by seven other constellations. Corona Australis and Scorpius border it to the north and Apus to its south. Other constellations near its boundaries are Norma, Triangulum Australe, Pavo, and Telescopium.
We can use the bright constellation of Scorpius as our guide in spotting Ara the Altar. If we can identify its stinger, which has a fish hook shape, we can then find our way towards Ara, under it.
When To See the Ara Constellation
Ara is a summer constellation in the northern hemisphere. We can see it in July at 9 pm. Other constellations we can see during that time are Draco, Hercules, and the constellations bordering Ara.
Ara can be seen during the winter months from the southern hemisphere.
Ara and Its Stars
The celestial altar has a considerable presence of stars because of its proximity to the Milky Way. However, it does not have many bright stars. Two of its stars were given the formal names, Cervantes and Inquill, as approved by the IAU.
Today, eighteen stars in this constellation were given the Bayer designations Alpha to Sigma by Nicolas-Louis de Lacaille. It is an addition to the eight stars previously designated by Johann Bayer. Some of them share the same Greek letter designations.
Alpha Arae (α Arae)
Alpha Arae belongs to the B2 Vne spectral class. Its apparent magnitude changes between 2.76 and 2.90 since it is a variable Be star. It is the second brightest star in the Altar constellation.
It has an equatorial bulge caused by its rapid rotation. Its mass is 9.6 times that of the Sun’s and is shining with the brightness of 5,800 solar luminosities. It has a visual companion, CCDM J17318-4953B. They look close enough to each other in our line of sight but are not physically related in space.
Alpha Arae is also called by the name Choo, though it is not among the list of names approved by the IAU. It lies at around 270 light-years away.
Beta Arae (β Arae)
Beta Arae is the brightest star in the Ara constellation. Its stellar classification is K3 Ib-IIa, indicating that it had already exhausted its hydrogen. We can see it in the naked eye as it has an apparent magnitude of 2.8.
This star is 8.21 as massive as the Sun. It is much more luminous than the star of our Solar System as it shines with the brightness of 5,636 Suns. It is an enlarged star that seems to be a slow rotator. Beta Arae is about 650 light-years from our planet.
Gamma Arae (γ Arae)
Gamma Arae ranks as the fourth brightest star in Ara. It is a supergiant star with a lower luminosity, belonging to the B1 Ib spectral class. Its radius is 23 times the radius of the Sun. This star is shedding mass and is estimated to have 12.5 to 25 solar masses. It is said to be only 15.7 million years old, much younger than our Sun. Gamma Arae is 1,110 light-years away from us.
Delta Arae (δ Arae)
Delta Arae is a double star of 3.62 apparent magnitude. It is a fast-spinning star with the stellar classification B8 Vn. The companion star is in the spectral class G8 V. Delta Arae is approximately 198 light-years away from our home planet, Earth.
Epsilon1 Arae (ε1 Arae)
Epsilon1 Arae is an orange-hued star that is more massive than our Sun. It has the stellar classification of K3 III. The radius of this star is nearly 33.7 times the Sun’s radius. It is 1.7 billion years old and is 360 light-years away from us. It is separated to Epsilon2 Arae by 0.54°. Epsilon1 Arae shares the Epsilon designation with another star.
Epsilon2 Arae (ε2 Arae)
Epsilon2 Arae is a double star whose apparent magnitude is 5.3. The brighter component has a relatively high abundance of iron, in the F5 V Fe+0.5 stellar class. The angular separation of the fainter companion is 0.590 arcseconds. It is 89 light-years distant.
Zeta Arae (ζ Arae)
Zeta Arae is the third-brightest point in Ara, having an apparent magnitude of 3.1. This giant star has the stellar classification of K3 III. It has a mass of 7 to 8 times that of the Sun and is as luminous by 3,800 times. It lies at a distance of 490 light-years. Zeta Arae is also known by the name Tseen Yin.
Eta Arae (η Arae)
Eta Arae is an orange-hued star with an apparent magnitude of 3.76. It is a giant star with the stellar classification K5 III. This slow-spinning star is nearly five billion years old. It is about 299 light-years away.
Theta Arae (θ Arae)
Theta Arae is a supergiant with a blue-white hue. Its apparent magnitude is 3.67, so we can see it in the unaided eye. It belongs in the stellar class B2 Ib. It is 8.9 times as massive as the Sun. The outer temperature of this star is much hotter than the Sun’s. It is located 810 light-years away from the Earth.
Iota Arae (ι Arae)
Iota Arae is a Be star in the stellar class B2 IIIne. This fast-spinning star is surrounded by circumstellar gas. Its apparent magnitude is 5.25. It is approximately 8.3 times as massive as our Sun. Iota Arae is 930 light-years distant from us.
Kappa Arae (κ Arae)
Kappa Arae is a yellow star of 5.21 apparent magnitude. Its stellar classification is G8 III, radiating at 4,950 K effective temperature. This giant star has a radius 14 times that of our Sun’s. It has two faint optical companions, one has an angular distance of 25 arcseconds and the other 30 arcseconds. Kappa Arae is 460 light-years away from us.
Lambda Arae (λ Arae)
Lambda Arae is an F-type main-sequence star. It belongs in the F4 V stellar class and has an apparent magnitude of 4.77. The effective temperature of this yellow-white star is 6,725 K. It shines with a luminosity of 4.6 Suns. A debris disk is suspected to surround it. Lambda Arae is roughly 70 light-years away from the Earth.
Cervantes (μ Arae)
Cervantes is the official name given to the star Mu Arae in the Bayer designation. It is also known as HD 160691 in the Henry Draper Catalogue. This G-type star is comparable to our Sun which is also in the G class. The stellar classification of Mu Arae is G3IV–V and it is most likely becoming a subgiant. It has a radius that is 1.36 times the solar radius and is about 1.10 times as massive as our Sun. This star is 51 light-years distant from us.
A planetary system was discovered in Cervantes. It hosts four exoplanets. In order from this star, the exoplanets are Mu Arae c (Dulcinea), Mu Arae d (Rocinante), Mu Arae b (Quijote), and Mu Arae e (Sancho)
Cervantes is named after the Spanish writer Miguel de Cervantes Saavedra. The extrasolar planets surrounding it were named after the characters in the said author’s work, El Ingenioso Hidalgo Don Quixote de la Mancha.
Nu1 Arae (ν1 Arae)
Nu1 Arae is a multiple star system. It is also known as V539 Arae. This triple star system is composed of a pair of B-type stars and an A-type third component. The pair have the stellar classifications of B2 V and B3 V. They form an eclipsing binary from our perspective here on Earth, which affects their 5.65 combined apparent magnitude. The two have an orbital period of 3.169 days.
The third component belongs to the spectral class A1 V. It has an apparent magnitude of 9.40. The Nu1 Arae star system is located about 1,000 light-years away from us.
Nu2 Arae (ν1 Arae)
Nu2 Arae is a B-type star of stellar class B9.5 III-IV. It is between the subgiant and giant stages of stellar evolution. The apparent magnitude of this star is 6.10. It is 85 times as luminous as the Sun. Nu2 Arae is about 570 light-years distant from Earth.
Pi Arae (π Arae)
Pi Arae has the stellar classification of A5 IV-V. It is faintly observable to the naked eye as its apparent magnitude is +5.25. The radius of Pi Arae is almost twice the solar radius. It has a mass that is 1.73 times that of the Sun’s. This 319 million-year-old star is 70 light-years away from the Sun.
Rho1 Arae ( ρ1 Arae)
Rho1 Arae is a spectroscopic binary that is in the spectral type B3 Vnpe. Its apparent magnitude is +6.275, making it one of the faintest stars that was assigned a Greek letter, or the Bayer designation. It was the French astronomer Nicolas Lacaille who first catalogued this star.
The orbital period of the spectroscopic binary is approximately 0.439 days. Its primary star is a fast-spinner. Rho1 Arae is estimated to be 640 light-years away from the Sun.
Rho2 Arae ( ρ2 Arae)
Rho2 Arae is a star with a blue-white hue. It is either in the B9 IV or B9 V stellar class. The apparent visual magnitude of this star is 5.54. It is more luminous than the Sun, shining with the brightness of 238 Suns. The mass of Rho2 Arae is 3.42 solar masses. It is approximately 520 light-years away from our Sun.
Sigma Arae (σ Arae)
Sigma Arae is an A-type star of +4.575 apparent magnitude. It is a main-sequence star with the stellar classification A0 V. It is 380 light-years distant.
Inquill (HD 156411)
Inquill is the official name given to the star HD 156411. It is a G-type star with the spectral type G1Vw. Its apparent magnitude is 6.67. HD 156411 is located roughly 179 light-years away. An exoplanet was discovered to orbit around this star. It was given the designation HD 156411 b.
Gliese 676 is a binary star system with an apparent magnitude of 9.59. The components of this system are M-type stars with a long orbital period of more than 20,000 years. They are designated Gliese 676 A and Gliese 676 B. The system is about 54 light-years away.
Four exoplanets were discovered in Gliese 676, around its primary star. In order from Gliese 676 A, the exoplanets are:
- 1- Gliese 676 A d
- 2- Gliese 676 A e
- 3- Gliese 676 A b
- 4- Gliese 676 A c
Gliese 674 is a red dwarf star with the stellar classification of M3V. The apparent magnitude of this M-type star is 9.38. It is approximately 15 light-years away from us. An exoplanet called Gliese 674 b orbits around this red dwarf.
HD 154857 is a G-type star with an apparent magnitude of 7.25. It has the stellar classification of G5IV-V. It hosts two extrasolar planets namely HD 154857 b and HD 154857 c. This planetary system is about 209 light-years away.
HD 152079 is in the spectral class G6V. its apparent magnitude is about 9.16. Its planetary system is located approximately 287 light-years from us.
HD 154672 is a G-type star that is similar to our Sun. It has the stellar classification of G3 IV. The mass of this star is 1.06 times the Sun’s mass. It is about 214.6 light-years distant from our planet.
HD 154672 is host to the gas giant HD 154672 b.
Planets in the Altar’s Constellation
Seven stars in Ara are discovered to have exoplanets, with some having four exoplanets at most.
Mu Arae c
Mu Arae c is the innermost planet in the Mu Arae planetary system. This hot-Neptune or mega-Earth has an orbital period of 9.64 days. The mass of this exoplanet equals that of 10.56 Earths. It was discovered in 2004 and was given the formal name Dulcinea.
Mu Arae d
Mu Arae d is most likely a gas giant. The mass of this exoplanet is roughly half (0.522) that of Jupiter’s. It is within the habitable zone of the Mu Arae planetary system, having an orbital period of 311 days. The Mu Arae d object was officially named Rocinante.
Mu Arae b
Mu Arae b or HD 160691 b is a massive exoplanet. This gas giant has a mass of 1.676 Jupiters. It completes an orbit of its star in 643 days. This exoplanet is given the official name Quijote. It is in the habitable zone of its planetary system.
Mu Arae e
Mu Arae e is a gas giant that is 5.24 AU from its star. The mass of this exoplanet is comparable to that of Jupiter, the most massive planet in our solar system. Mu Arae e has a mass of 1.814 Jupiters and an orbital period of 4,206 days. This extrasolar planet was later on given the name Sancho.
Gliese 676 A d
Gliese 676 A d, also known as GJ 676 A d, is an exoplanet of the super-Earth type. It was discovered in 2012 using the Radial Velocity method. This extrasolar planet has a mass of 4.4 Earths. It has an orbital period of 3.6 days.
Gliese 676 A e
Gliese 676 A e has a mass of 8.1 Earths. This Neptune-like exoplanet orbits an M-type star in a period of 35.4 days. It was discovered in 2012. Its planetary system is around 54 light-years away from Earth.
Gliese 676 A b
Gliese 676 A b (GJ 676 A b) is a gas giant. It is as massive as 6.7 Jupiters. It has an orbital period of 2.9 years or roughly 1,050 days. Radial Velocity was used for the discovery of Gliese 676 A b, just like how other exoplanets in the system were detected.
Gliese 676 A c
Gliese 676 A c belongs to the gas giant type of exoplanets. It has a mass of 6.8 Jupiters. Among the four exoplanets of its planetary system, it is the farthest from its star. It has a longer orbital period of 20.1 years or about 7,340 days.
HD 154857 b
HD 154857 b is one of the two exoplanets in its planetary system. It has a mass that is 2.45 times that of Jupiter’s. It is 1.29 AU from the G-type star HD 154857 and has an orbital period of 408.6 days. This exoplanet was discovered by the Anglo-Australian Planet Search (AAPS) in 2004.
HD 154857 c
HD 154857 c was discovered in 2014. It is a gas giant that has a mass of 2.58 Jupiters. This exoplanet has an orbital radius of 5.36 AU and completes its orbit in 9.5 years or about 3,452 days.
Gliese 674 b
Gliese 674 b or GJ 674 b is classified as a Neptune-like exoplanet. It is 0.039 AU from the star Gliese 674 and has an orbital period of 4.7 days. The mass of this gas giant is 11.09 Earths. It was discovered in 2007.
HD 152079 b
HD 152079 b is an exoplanet that is mainly composed of gas. This gas giant has a mass of 2.661 Jupiters. It completes one full orbit in 8 years. Its orbital radius is 4.187 AU. It was discovered in 2009.
HD 154672 b
HD 154672 b is a giant planet that has a mass of 5.37 Jupiters. Its orbital period is 163.9 days. This gas giant was discovered in 2008. It orbits a yellow star in a planetary system that is more than 200 light-years away from us.
HD 156411 b
HD 156411 b is an exoplanet that is in the habitable zone of its planetary system. It is a gas giant that orbits the G-type star Inquill. Because of that, it is also called Inquill b. The mass of this exoplanet is 0.74 Jupiters. Its orbital period is 2.3 years.
Deep-sky Objects in Ara Constellation
Ara constellation has a lot of deep-sky objects that spark the curiosity of many. The flaring black hole GX 339-4 is just an example. It hosts the star-forming region called RCW 108 and the pre-planetary nebula known as the Water Lily Nebula.
It has no Messier objects but it has many interesting galaxies like NGC 6215, NGC 6328, and NGC 6221 as well as star clusters like NGC 6193, NGC 6200, NGC 6208, and NGC 6204.
The Stingray Nebula is also known as Hen 3-1357. It is a planetary nebula that is 8,000 light-years distant. So far, it is the youngest planetary nebula discovered. Its central star in the middle has a fainter companion. This nebula is 130 times the size of the solar system. Images show that it has undergone changes in shape and brightness over the years.
NGC 6326 is a planetary nebula. Observers have likened it to a “holiday ornament” because of its wisps of gas. The glowing color is caused by the central star in this nebula which is already at the late stage of its life. It is located 11,000 light-years away from us.
NGC 6300 is a Seyfert II spiral galaxy. It has an unusually bright centre and is suspected to contain a black hole that is much more massive than our Sun. The apparent magnitude of this celestial object is 8.78. It is 50.9 million light-years from our planet.
NGC 6328 is between a barred and an unbarred spiral galaxy. Its apparent magnitude is 7.64. This intermediate spiral galaxy was discovered in 1835 by astronomer John Herschel. It is estimated to be 199 million light-years distant from Earth.
Westerlund 1 (Ara Cluster)
Westerlund 1 is a super star cluster (SSC). This young open cluster is one of the most massive of its kind in the Milky Way galaxy. It contains some of the most unique stars known such as the red supergiant Westerlund 1-26, many Wolf-Rayet stars, OB supergiants, and many others.
This star cluster is 15,000 light-years away, a distance that is relatively close for astronomers to conduct observations and studies. It is predicted to become a globular cluster in the future.
NGC 6397 is a globular cluster that has an apparent magnitude of 6.7. It is sometimes called Caldwell 86. It is located about 7, 200 light-years away from us, making it the second-closest globular to our planet. The first one being Messier 4 in the constellation of Scorpius.
There are about half a million stars in NGC 6397. They have already evolved away from the main sequence, so they are expected to be of low mass. However, astronomers have observed the presence of blue straggler stars. These stars are bluer and more massive than the rest of the stars in the cluster. NGC 6397 has been an object of interest because of the presence of these blue stragglers.
Mythology Related to Ara Constellation
Several stories surround the Ara constellation. If we look up at the night sky, we can see the nearby constellations of Lupus the Wolf and Centaurus the Centaur.
The two are depicted in action, with Centaurus piercing Lupus with a spear. The wolf would then be sacrificed in Ara the Altar. Some say that the altar itself was built by the gigantic Cyclopes. The most famous myths associated with this constellation is that of the epic battle of overthrowing the Titans and the story of King Lycaon.
Ara in the Titanomachy
The Titans Cronus and Rhea ruled the world after overthrowing their father Uranus. Later on, Cronus came to know of a prophecy that he will have the same fate as his father. He was afraid that his children would take over him and take his power so he thought it would be better to get rid of them. He swallowed his children Demeter, Poseidon, Hera, Hestia, and Hades the minute after their birth. They would later become the first generation of Olympian gods.
Rhea feared for the life of her next child, so she gave birth to Zeus in secret. She hid the baby in a cave and gave a stone to Cronus instead. The Titan swallowed the stone thinking that it was Zeus.
When Zeus grew up, Gaia gave him an emetic which he used to make his father vomit his brothers and sisters. The siblings came together and vowed to put an end to their father and the Titans. An allegiance was made in an altar, starting the Titanomachy or the ten-year war. This war is also known as the Titan Wars.
In the end, the Olympians won and they became the new ruler of the world. Zeus led them as the god of the sky while the others also have their own roles.
To honor their great victory, Zeus placed the altar where they vowed to take over Cronus. This altar became the Ara constellation.
Ara and the Story of King Lycaon
King Lycaon of Arcadia wanted to test Zeus. One day, during a court feast, he decided to make an offering to the gods in his burning altar. He chose to sacrifice Arcas, the son of Callisto and Zeus. The king said that Zeus can prove his power and ability as a god if he can bring Arcas back from the dead and unharmed. Zeus restored Arcas to life and in his anger, turned King Lycaon into a wolf.
Another version of the story narrates that King Lycaon tested the all-knowing power of Zeus by tricking him. Lycaon presented a meal to the King of the gods that contained the flesh of his own son, Nyctimus. But Zeus was not fooled. He saw behind the trickery and punished the king by turning him into the first wolf. He also killed the 50 sons of King Lycaon.
The constellation of Ara is said to be the altar of King Lycaon of Arcadia where he made his offerings to the gods.