Wednesday, 18 October, 2017
The Aquarius Constellation

The Aquarius Constellation

The Aquarius Constellation.

Aquarius is a constellation of the zodiac, situated between Capricornicus and Pisces. Its name is Latin for “water-carrier” or “cup-carrier”, and its symbol is  , a representation of water. Aquarius is identified as GU.LA “The Great One” in the Babylonian star catalogues and represents the god Ea himself, who is commonly depicted holding an overflowing vase. In Greek mythology, Aquarius is sometimes associated with Deucalion, the son of Prometheus who built a ship with his wife Pyrrha to survive an imminent flood. They sailed for nine days before washing ashore on Mount Parnassus. The Constellation is one of the oldest of the recognised constellations along the zodiac (the Sun’s apparent path). It was one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations. It is found in a region often called the Sea due to its profusion of constellations with watery associations such as Cetus the whale, Pisces the fish, and Eridanus the river. Its position in the sky is right ascension at 23 hours, declination at -23 degrees, between latitudes 65 and -90 degrees, and the Constellation is best seen at 9.00pm in October.

Despite both its prominent position on the zodiac and its large size, Aquarius has no particularly bright stars, its four brightest stars being less than magnitude 2. However, recent research has shown that there are several stars lying within its borders that possess planetary systems. The two brightest stars, Alpha and Beta Aquarii, are luminous yellow supergiants, of spectral types G0Ib and G2Ib respectively, that were once hot blue-white B-class main sequence stars 5 to 9 times as massive as the Sun. The two are also moving through space perpendicular to the plane of the Milky Way. Just shading Alpha, Beta Aquarii is the brightest star in Aquarius with an apparent magnitude of 2.91. It also has the proper name of Sadalsuud. Having cooled and swollen to around 50 times the Sun’s diameter, it is around 2200 times as luminous as the Sun. It is around 6.4 times as massive as the Sun and around 56 million years old. Sadalsuud is 540 ± 20 light-years from Earth. Alpha Aquarii, also known as Sadalmelik, has an apparent magnitude of 2.94. It is 520 ± 20 light-years distant from Earth, and is around 6.5 times as massive as the Sun and 3000 times as luminous. It is 53 million years old.

Twelve exoplanet systems have been found in Aquarius as of 2013. Gliese 876, one of the nearest stars to Earth at a distance of 15 light-years, was the first red dwarf star to be found to possess a planetary system. It is orbited by four planets, including one terrestrial planet 6.6 times the mass of Earth. The planets vary in orbital period from 2 days to 124 days. 91 Aquarii is an orange giant star orbited by one planet, 91 Aquarii b. The planet’s mass is 2.9 times the mass of Jupiter, and its orbital period is 182 days. Gliese 849 is a red dwarf star orbited by the first known long-period Jupiter-like planet, Gliese 849b. The planet’s mass is 0.99 times that of Jupiter and its orbital period is 1,852 days. Other less prominent systems include WASP-6, HD 206610, and WASP-47.

M 2


M 73

Because of its position away from the galactic plane, the majority of deep-sky objects in Aquarius are galaxies, globular clusters, and planetary nebulae. Aquarius contains three deep sky objects that are in the Messier catalogue: the globular clusters Messier 2Messier 72, and the open cluster Messier 73. Two well-known planetary nebulae are also located in Aquarius: the Saturn Nebula (NGC 7009), to the southeast of μ Aquarii; and the famous Helix Nebula (NGC 7293), southwest of δ Aquarii. M2, also catalogued as NGC 7089, is a rich globular cluster located approximately 37,000 light-years from Earth at magnitude 6.5. M72, also catalogued as NGC 6981, is a small 9th magnitude globular cluster located approximately 56,000 light-years from Earth. M73, also catalogued as NGC 6994, is an open cluster with highly disputed status. Aquarius is also home to several planetary nebulae. NGC 7009, also known as the Saturn Nebula, is an 8th magnitude planetary nebula located 3,000 light-years from Earth. NGC 7293, also known as the Helix Nebula, is the closest planetary nebula to Earth at a distance of 650 light-years. It covers 0.25 square degrees, making it also the largest planetary nebula as seen from Earth. However, because it is so large, it is only viewable as a very faint object, though it has a fairly high integrated magnitude of 6.0.

NGC 7009 has a bright central star at the centre of a dark cavity bounded by a football-shaped rim of dense, blue and red gas. The cavity and its rim are trapped inside smoothly-distributed greenish material in the shape of a barrel and comprised of the star’s former outer layers. At larger distances, and lying along the long axis of the nebula, a pair of red ‘ansae’, or ‘handles’ appears. Each ansa is joined to the tips of the cavity by a long greenish jet of material. The handles are clouds of low-density gas. NGC 7009 is 1, 400 light-years away in the constellation Aquarius. The Hubble telescope observation was taken April 28, 1996 by the Wide Field and Planetary Camera 2.

There are three major meteor showers with radiants in Aquarius: the Eta Aquariids, the Delta Aquariids, and the Iota Aquariids. The Eta Aquariids are the strongest meteor shower radiating from Aquarius. It peaks between 5 and 6 May with a rate of approximately 35 meteors per hour. The parent body of the shower is Halley’s Comet, a periodic comet. The Delta Aquariids is a double radiant meteor shower that peaks first on 29 July and second on 6 August. The Iota Aquariids is a fairly weak meteor shower that peaks on 6 August, with a rate of approximately 8 meteors per hour.

Credit: Wikipedia.