Fig 1. Aquarius. © 2003 Torsten Bronger.
Fig 2. Aquarius Dwarf.
Aquarius (abbreviation: Aqr), the Water-bearer, is a large but quite faint southern constellation and the twelfth sign of the zodiac. It is surrounded by Pegasus, Equuleus, and Delphinus to the north, Aquila to the west, Capricornus so the southwest, Pisces Austrinus and Sculptor to the south, and Cetus to the east.
The stars Sadachbia (Gamma), Eta Aqr, Zeta Aqr, and Pi Aqr form a small Y-shaped asterism, called the Water Jar or Urn, thought to mark the Water-bearer's cup.
See below for details of the constellation's brightest stars and interesting deep sky objects.
|R Aquarii. Hubble Space Telescope image.
R Aquarii is a symbiotic star thought to consist of a white dwarf and a Mira variable in a binary system. At a distance of about 710 light-years it is one of the nearest symbiotic stars to the Sun. It has been suggested that the nebula around R Aquarii is the remains of nova-like outburst, which may have been observed by Japanese astronomers in 930 AD.
The Aquarids are either of two distinct meteor showers with a radiant in Aquarius. The Eta Aquarids are observed between about 28 April and 21 May, peaking around May 5 or 6. This is a fine southern shower, associated with Halley's Comet. Typical meteor velocity is 67 km/s (42 miles/sec). The radiant is at RA 22h 20m, Dec –1°.
The Delta Aquarids occur between 14 July and 18 August, peaking on 29 July and 7 August. Meteor velocity is about 42 km/s (26 miles/sec). The radiant is double, the two components lying at RA 22h 36m, Dec –17° and RA 23h 04m, Dec +2°.
The Aquarius Dwarf is an irregular galaxy (type ImV) and member of the Local Group. It lies about 3.2 million light-years from the Milky Way Galaxy in Aquarius (RA 20h 47m, Dec –12° 51'). It was first catalogued in 1959 by the DDO survey.
Although the Aquarius Dwarf contains significant amounts of neutral hydrogen – the raw material needed to make new stars – it displays a very low level of star formation, which results in it being one of the least luminous members of the Local Group Local Group. It has been conjectured that this is connected to its spatial isolation.
|Stars in Aquarius brighter than magnitude 4.0|
|star||vis mag||abs mag.||spec type||distance (ly)||RA (h m s)||Dec (° ' ")|
|Beta (Sadalsuud)||2.90||-3.47||G0Ib||612||21 31 33||-05 34 16|
|Alpha (Sadalmelik)||2.95||-3.88||G2Ib||759||22 05 47||-00 19 11|
|Delta (Skat)||3.27||-0.18||A3V||159||22 54 39||-15 49 15|
|Zeta||3.65||1.14||F6IV+F3V||103||22 28 50||-00 01 12|
|c2||3.68||-0.60||K1III||234||23 09 27||-21 10 21|
|Lambda||3.73||-1.67||M2.5IIIaFe||392||22 52 37||-07 34 47|
|Epsilon (Albali)||3.78||-0.46||A1V||230||20 47 40||-09 29 45|
|Gamma (Sadachbia)||3.86||0.43||A0V||158||22 21 39||-01 23 14|
|b1||3.96||0.48||K0III||162||23 22 58||-20 06 02|
|Other objects of interest|
|name||type of object||notes|
|V1344 Aqr||star||An X-ray jet variable|
|Helix Nebula||planetary nebula||NGC 7293. See separate entry|
|Saturn Nebula||planetary nebula||NGC 7009. See separate|
|M2 (NGC 7089)||globular cluster||On of the most impressive of its type; it appears in binoculars as a misty patch with a central concentration, and with a 15-cm telescope is partially resolved into stars. Magnitude 6.5, diameter 12.9', distance 37,500 light-years; RA 21h 31m, Dec -01° 03'|
|M72 (NGC 6981)||globular cluster||A faint object in small telescopes. Magnitude 9.8, diameter 2', distance 55,400 light-years; RA 20h 52m, Dec -12° 39'|
|Atoms for Peace Galaxy||galaxy||NGC 7252. See separate entry|
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