Stars Despite both its prominent position on the zodiac and its large size, Aquarius has no particularly bright stars, its four brightest stars being less bright than (The Apparent Magnitude scale is reverse logarithmic, with increasingly bright objects having lower and lower (more negative) magnitudes.) Recent research has shown that there are several stars lying within its borders that possess
planetary systems. File:Aquarius (Annotated) (aquarius-ann).tiff|thumb|left|upright=1.25|The constellation Aquarius showing the IAU boundaries, the constellation stick figure, and labels for its brightest stars. Astrophotograph by Eckhard Slawik, from NOIRLab's 88 Constellations project. Aquarius is characterized by a Y-shaped asterism historically called "The Water Jar" that consists of Gamma, Pi, Eta, and
Zeta Aquarii; it is nicknamed the "Steering Wheel" by some modern observers. The two brightest stars,
α Aquarii and β Aquarii, are luminous yellow supergiants, of spectral types G0Ib and G2Ib respectively, β Aquarii is the brightest star in Aquarius with apparent – only slightly brighter than α Aquarii. 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 from Earth. α Aquarii, also known as
Sadalmelik, has apparent It is distant from Earth,
γ Aquarii, also called
Sadachbia, is a white main sequence star of spectral type star of spectral type A0V that is between 158 and 315 million years old and is around 2.5 times the Sun's mass (), and double its radius. Its magnitude is 3.85, and it is away, Of these, as many as four may lie within the system's
habitable zone, and may have liquid water on their surfaces. The discovery of the TRAPPIST-1 system is seen by astronomers as a significant step toward finding life beyond Earth.
Deep-Sky Objects J2240 lies in the constellation of Aquarius 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 catalog: the globular clusters
Messier 2,
Messier 72, and the asterism
Messier 73. While M73 was originally catalogued as a sparsely populated open cluster, modern analysis indicates the 6 main stars are not close enough together to fit this definition, reclassifying M73 as an asterism. 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, it is viewable in small-
aperture instruments, but a 100 mm aperture
telescope is needed to resolve any stars. 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. It was given its moniker by the 19th century astronomer
Lord Rosse for its resemblance to the planet
Saturn in a telescope; it has faint protrusions on either side that resemble
Saturn's rings. It appears blue-green in a telescope and has a central star of magnitude 11.3. Compared to the Helix Nebula, another planetary nebula in Aquarius, it is quite small.
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. One of the visible galaxies in Aquarius is
NGC 7727, of particular interest for amateur astronomers who wish to discover or observe
supernovae. A
spiral galaxy (
type S), it has an
integrated magnitude of 10.7 and is 3 by 3 arcseconds.
NGC 7252 is a tangle of stars resulting from the collision of two large galaxies and is known as the Atoms-for-Peace galaxy because of its resemblance to a cartoon atom.
Meteor showers 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. Originally discovered by Chinese astronomers in 401, Eta Aquariids can be seen coming from the Water Jar beginning on 21 April and as late as 12 May. The
parent body of the shower is
Halley's Comet, a
periodic comet.
Fireballs are common shortly after the peak, approximately between 9 May and 11 May. The normal meteors appear to have yellow trails. The Delta Aquariids is a double radiant meteor shower that peaks first on 29 July and second on 6 August. The first radiant is located in the south of the constellation, while the second radiant is located in the northern circlet of Pisces asterism. The southern radiant's peak rate is about 20 meteors per hour, while the northern radiant's peak rate is about 10 meteors per hour. The Iota Aquariids is a fairly weak meteor shower that peaks on 6 August, with a rate of approximately 8 meteors per hour. ==Astrology==