In this article, we’ll be sharing with you everything you need to know about this constellation, including how to find it, deep space objects contained within it and how to use it to find other night sky objects more easily.
The Constellation of Aquarius
This constellation was known to several ancient cultures. The Ancient Babylonians associated it with Ea, creator and protector of humanity and the Ancient Egyptians associated it with Hapi, God of the Nile River.
Aquarius means ‘the water bearer’ in Latin, and is one of the constellations that Greek astronomer Ptolemy cataloged over 2000 years ago.
In Greek mythology, Aquarius often represents Ganymede, the son of King Tros. Zeus disguised himself as an eagle and carried the handsome youth to the heavens where he would serve as the cupbearer to the gods. In another Greek myth, Aquarius represents Deucalion (a virtuous man). Zeus sent a great flood to punish people for their misdeeds and advised Deucalion to build an ark to save himself.
To help you spot Aquarius, here’s what SkySafari 6 shows.
Aquarius has an area of 980 square degrees making it the 10th largest of the 88 recognized constellations.
If you’ve observed the annual Eta Aquariids meteor shower (which peaks ~May 4) you may recognize this constellation as the location of the radiant is near Eta Aquarii. The radiant of the annual Delta Aquariids meteor shower (which peaks ~July 28) is near Delta Aquarii.
Aquarius is also known for its y-shaped ‘Water Jar’ asterism which consists of the stars Zeta Aquarii, Eta Aquarii, Pi Aquarii, and Gamma Aquarii.
In the image below, showing the extent of the constellation, you can see the ‘Water Jar’ asterism stars
In the next section discover how to find Aquarius.
How To Find Aquarius In The Night Sky
Aquarius is part of the zodiac family of constellations and is visible to observers at latitudes between +65° and -90°. It never rises more than midway between horizon and overhead from mid-latitudes of the US.
Northern Hemisphere observers can see it in the evening from November to April. It’s highest in the late evening of mid-January. Southern Hemisphere observers can see it in the spring.
The constellation of Aquarius is bordered by the constellations Aquila, Capricornus, Cetus, Delphinus, Equuleus, Pegasus, Pisces, Piscis Austrinus and Sculptor.
To find Aquarius, do a naked-eye search for ‘The Great Square of Pegasus‘. Draw an imaginary line from Alpheratz to Markab (~20°), extend this line ~7° to Homan (Zeta Peg), 9° to Baham (Theta Peg), then hop 6° south to Sadalmelik (Alpha Aquarii).
Alternatively, the wings of Cygnus the Swan point to Aquarius, passing by the Markab corner of the Great Square of Pegasus.
You can measure these distances with your hand at arm’s length, as shown in this article (link opens a new page).
To find Aquarius’s exact position for your location on any night, use software such as Stellarium (free) or SkySafari.
Aquarius’s Brightest Stars
Aquarius is a large constellation and contains several bright stars. Only two are brighter than magnitude 3, but there are more than 30 that are magnitude 5.0 or brighter.
The star chart below, from Sky Safari, shows each of those brighter stars. Details for the most important ones are given below that.
Alpha Aquarii (Sadalmelik) – This double star is the second brightest star in Aquarius. The magnitude 2.94, yellow-orange, supergiant, primary and magnitude 12.20, secondary component are 110.0 arcseconds apart. It’s 750 light-years away. ‘Sadalmelik’ means ‘the lucky stars of the king’ in Arabic. Sadalmelik lies within 1° of the celestial equator.
Beta Aquarii (Sadalsuud) – This double star is the brightest star in Aquarius. The magnitude 2.89, yellow-orange, supergiant, primary and magnitude 11.00, secondary component are 37.6 arcseconds apart. It’s 600 light-years away. ‘Sadalsuud’ means ‘the luckiest of all of them’ in Arabic.
Gamma Aquarii (Sadachbia) – This variable double star is the sixth brightest star in Aquarius and is the westernmost star in the ‘Water Jar’ asterism. The magnitude 3.84, blue-white, main sequence, primary and magnitude 12.20, secondary component are 33.3 arcseconds apart. This is an eruptive variable ranging in magnitude from 3.84 to 3.89. Sadachbia is 158 light-years away. ‘Sadachbia’ means ‘the lucky star of the tents’ in Arabic.
Delta Aquarii (Skat) – This magnitude 3.26, white, main sequence, variable star is the third brightest star in Aquarius. This eruptive variable ranges in magnitude from 3.25 to 3.29 and is 161 light-years away.
Epsilon Aquarii (Albali) – This magnitude 3.76, white, main sequence star is 208 light-years away. Its mass is 2.7 Solar masses, its diameter is 4.3 Solar diameters and it’s 1.6 times hotter than the Sun.
Zeta1 Aquarii (Sadaltager) – This double star is the fourth brightest star in Aquarius and marks the center of the ‘Water Jar’ asterism. The magnitude 3.65, yellow-white, subgiant, primary and magnitude 4.34, secondary component are 2.3 arcseconds apart. Sadaltager is 189 light-years away.
Zeta2 Aquarii – This variable double star marks the center of the ‘Water Jar’ asterism and is 103 light-years away. The magnitude 4.09, yellow-white, subgiant, primary and magnitude 4.48, secondary component are 2.3 arcseconds apart. This is an erupting variable with a minimum magnitude of 3.65.
Eta Aquarii – This magnitude 4.03, blue-white, subgiant is the easternmost star in the ‘Water Jar’ asterism. Eta Aquarii is 185 light-years away.
Theta Aquarii – This magnitude 4.17, yellow-orange, bright giant is 187 light-years away. Its mass is 1.1 Solar masses, its diameter is 13.2 Solar diameters and it’s 17% cooler than the Sun.
Iota Aquarii – This magnitude 4.28, blue-white, subgiant is 175 light-years away. Its mass is 3.3 Solar masses, its diameter is 2.5 Solar diameters and it’s 1.8 times hotter than the Sun.
Kappa Aquarii (Situla) – This double star is 214 light-years away. The magnitude 5.03, orange giant, primary and 12.20, secondary component are 84.4 arcseconds apart. This may be a multiple system.
Lambda Aquarii (Hydor) – This variable double star is the fifth brightest star in Aquarius and marks the bend in the stream of water from the ‘Water Jar’ asterism. The magnitude 3.75, orange-red giant, primary and magnitude 8.30, secondary component are 0.5 arcseconds apart. This pulsating variable ranges in magnitude from 3.57 to 3.80 and is 84 light-years away. Hydor is less than 1/2° from the ecliptic and can be occulted by the Moon.
Mu Aquarii – This double star is 157 light-years away. The magnitude 4.71, yellow-white, primary and magnitude 9.85, secondary component are 503.2 arcseconds apart. This may be a multiple system.
Nu Aquarii – This magnitude 4.51, yellow-orange giant is 159 light-years away. Its mass is 1.1 Solar masses, its diameter is 9.6 Solar diameters and it’s 17% cooler than the Sun.
Xi Aquarii – This double star is 179 light-years away. The magnitude 4.69, white, main sequence, primary and magnitude 7.00, secondary component are 0.0 arcseconds apart.
Omicron Aquarii – This magnitude 4.75, blue-white subgiant is 435 light-years away. It’s an eruptive variable ranging in magnitude from 4.67 to 4.89.
Pi Aquarii (Seat) – This magnitude 4.80, blue-white star is the northernmost star in the ‘Water Jar’ asterism. It’s an eruptive variable ranging in magnitude from 4.42 to 4.87. It’s 338 light-years away. ‘Seat’ is Arabic for ‘lucky star of hidden things’.
Sigma Aquarii – This double star is 290 light-years away. The magnitude 4.82, blue-white, subgiant, primary and magnitude 8.47, secondary component are 3.7 arcseconds apart. This may be a multiple system.
Tau2 Aquarii – This variable double star is 318 light-years away. The magnitude 4.03, orange-red giant, primary and magnitude 9.93, secondary component are 132.4 arcseconds apart. This is an eruptive variable ranging in magnitude from 3.98 to 4.04.
Phi Aquarii – This magnitude 4.23, orange-red giant is 202 light-years away. It’s an eruptive variable with a mass of 1.2 Solar masses, diameter of 38.8 Solar diameters and temperature 37% cooler than the Sun.
Chi Aquarii – This variable double star is 640 light-years away. The magnitude 4.99, orange-red giant, primary and 5.90 magnitude, secondary component are 0.0 arcseconds apart. This pulsating variable ranges in magnitude from 4.75 to 5.10 with a period of 35.250 days.
Psi1 Aquarii – This double star is 150 light-years away. The magnitude 4.23, orange giant, primary and magnitude 9.88, secondary component are 48.9 arcseconds apart. This may be a multiple system.
Psi2 Aquarii – This magnitude 4.40, blue-white, main sequence star is 402 light-years away. This eruptive variable ranges in magnitude from 4.40 to 4.46 over a period of 1.0730 days.
Omega1 Aquarii – This magnitude 4.98, yellow-white subgiant is 142 light-years away. Its mass is 1.6 Solar masses, its diameter is 2.6 Solar diameters and it’s 1.3 times hotter than the Sun.
Omega2 Aquarii – This double star is 149 light-years away. The magnitude 4.48, blue-white, main sequence, primary and magnitude 9.89, secondary component are 5.5 arcseconds apart. This may be a multiple system.
88 Aquarii – This magnitude 3.68, orange giant is 291 light-years away. Its mass is 1.2 Solar masses, its diameter is 28.5 Solar diameters and it’s 22% cooler than the Sun.
Star Hopping From Aquarius
Although it has a lot of brightish stars, the lack of brighter, waymarking stars makes Aquarius a poor starting point for star hopping.
Objects To See Within Aquarius
Aquarius contains three Messier objects and few other deep sky objects suitable for small telescope users.
M2 (NGC 7098) – This globular cluster has a magnitude of 6.46 and an apparent size of 16.0 arcminutes. It’s 37,500 light-years away and is at right ascension 21h 34m 33s and declination -00° 43’ 41”.
M72 (NGC 6984) – This globular cluster has a magnitude of 9.27 and an apparent size of 6.6 arcminutes. It’s 55,000 light-years away and is at right ascension 20h 54m 38s and declination -12° 27’ 22”.
M73 (NGC 6994) – This y-shaped asterism has a magnitude of 8.89 and an apparent size of 9.0 arcminutes. It’s at right ascension 21h 00m 5s and declination -12° 33’ 0”.
NGC 7009 (Saturn Nebula, Caldwell 55) – This planetary nebula has a magnitude of 7.80 and an apparent size of 0.5 x 0.4 arcminutes. It’s 2,900 light-years away and is at right ascension 21h 05m 21s and declination -11° 16’ 50”.
NGC 7293 (Helix Nebula, Caldwell 63) – This planetary nebula has a magnitude of 7.59 and an apparent size of 14.7 x 12.0 arcminutes. It’s 650 light-years away and is at right ascension 22h 30m 49s and declination -20° 43’ 40”.
Summary
Aquarius is a large, dim constellation and contains several notable stars and some deep sky objects for small telescope users. Hop on over from the Great Square of Pegasus this winter.
