How to Find the Aquarius Constellation

Northern hemisphere autumn constellations.
Northern hemisphere autumn skies, view to the south.

 Carolyn Collins Petersen

The Aquarius constellation is one of several water-related star patterns in the sky. Take some time to look for this constellation in the night sky when it is most visible, starting in late October.

Finding Aquarius

Aquarius is visible from nearly the entire planet. It is bounded by several other constellations: Cetus (the sea monster), Pisces, Capricornus, Aquila, and Pegasus. Aquarius lies along the zodiac and ecliptic.

Aquarius constellation and three deep-sky objects.
A star chart showing Aquarius and three deep-sky objects. Carolyn Collins Petersen 

The Story of Aquarius

The constellation Aquarius was once called The Great One (or GU LA in the Babylonian language). Aquarius was linked to the god Ea, a figure that frequently appears in Babylonian artifacts. Ea was often associated with the floods that regularly visited the Babylonian part of the Middle East. 

Like the Babylonians, the ancient Egyptians saw the constellation as a god associated with flooding. Hindus saw the star pattern as a water pitcher, and in ancient China, the constellation was interpreted as a water jar with a stream flowing away from it.

The ancient Greeks had many tales about Aquarius, but mostly associated it with Ganymede, a Greek hero who ascended to Mount Olympus to serve as the cup-carrier to the gods. This depiction as a water-bearer stands to this day. 

The Stars of Aquarius

In the official IAU chart of Aquarius, the figure of the water bearer is accompanied by a number of other stars that exist in this region. The brightest star is called alpha Aquarii and, like beta Aquarii, is a yellow supergiant star. They are G-type stars and are several times more massive than the Sun. Alpha Aquarii also has the name Sadalmelik, while beta is also called Sadalsuud. 

The chart showing the constellation Aquarius.
The official IAU constellation star chart. IAU/Sky Publishing 

One of the most fascinating stars in this constellation is R Aquarii, a variable star. R Aquarii is made up of a pair of stars: a white dwarf and another variable, which orbit each other once every 44 years. As they circle their common center of gravity, the white dwarf member pulls material from its partner. Eventually, some of that material erupts off the white dwarf, which causes the star to brighten considerably. The pair has a nebula of material surrounding it called Cederblad 211. The material in the nebula may be associated with the periodic outbursts that this star pair experiences. 

A symbiotic star in the constellation Aquarius.
Image made from HST imagery of R Aquarii. The pair of stars is surrounded by material lost from one of the pair. STSCI/NASA/ESA/Judy Schmidt 

Avid meteor shower watchers may be familiar with the three showers that seem to emanate from Aquarius each year. The first is the Eta Aquariids, which on the 5th and 6th of May. This is the strongest of the three and can produce up to 35 meteors per hour. The meteors from this shower come from materials shed by Comet Halley as it travels through the solar system. The Delta Aquariids that peak twice: once on the 29th of July and again on the 6th of August. It's not quite as active as its sister shower in May, but still worth checking out. The weakest of the three is the Iota Aquariids, which peak on August 6th each year. 

Deep-sky Objects in Aquarius

Aquarius is not close to the plane of the galaxy where many deep-sky objects exist, but it nevertheless sports a treasury of objects to explore. Observers with good telescopes and binoculars can find galaxies, globular cluster, and a few planetary nebulae. The globular cluster M2 can be seen with the naked eye under good conditions, and a telescope reveals much more detail.

Globular cluster M2 in Aquarius.
M2 is a tightly packed globular cluster. It's shown here in an image by Sean X. Curry. Sean X Curry, CC BY-SA 4.0

Also worth exploring is a pair of planetary nebulae called the Saturn Nebula and the Helix Nebula. These are the remains of stars in their death processes. In the not-too-distant past, they gently pushed their outer atmospheres off to space, leaving behind beautiful glowing clouds surrounding the leftovers of their progenitor stars. In a few thousand years, the clouds will dissipate, leaving behind a pair of cooling white dwarfs.

The Helix Nebula as seen by HST and CTIO; bottom image is a 3D computer model of this dying star and its nebula. STScI/CTIO/NASA

For a more challenging observation activity, sky-gazers can seek out the galaxy NGC 7727. It lies about 76 million light-years away from us. Professional astronomers are studying long streamers of gas that emanate from the galaxy, which is classified as a "peculiar" galaxy due to its odd shape. NGC 7727 is likely in the final stage of a galaxy merger, and will eventually become a large elliptical galaxy in the distant figure.