Aquarius


Transit Date of principal star:
23 August


In Greek mythology Aquarius was Ganymede, "cup-bearer to the gods". Ganymede's story is told in "Aquila". His position was essentially to pour wine for all the gods on Olympus, a function far removed from the initial importance of the Water Bearer, as it first rose in Babylonia.

In fact, the constellation seems to have represented water in a number of ancient cultures. In Egypt, for instance, the constellation was thought to cause the Nile to give forth its annual floods. The waters of the Nile, far to the south, would start to rise in June as the rains from the Ethiopian highlands began to run off into the Blue Nile. The night sky, in June, would show Aquarius at its zenith: the bringer of water.


Even if alpha Aquarii is a supergiant, perhaps a hundred times the size of the Sun, since it's a thousand light years away it only shines with a 2.96 visual magnitude.

Alpha Aquarii ("Sadalmelik") and beta Aquarii ("Sadalsuud") are twin supergiants with nearly identical names. The names mean, respectively, "The Lucky One of the King" and "The Luckiest of the Lucky". Gamma Aquarii shares in the good fortune: "Sadachbia": "The Lucky Star of Hidden Things".

"Why is so much luck found in Aquarius", you may ask. When the sun entered Aquarius the new year was about to begin, Spring was on the horizon and the watery season would assure abundant crops. One can therefore appreciate the importance of the Water Bearer.

Incidentally, if the "Age of Aquarius" was celebrated in the 1960s, the real event is still some 600 years off: at that time Aquarius will contain the vernal equinox, marking the return of the Sun into the northern celestial hemisphere.


Aquarius has a few nice binaries, a unique variable, and a few deep sky objects of some interest (but the Messiers here are generally sub-par). The stars are generally fourth magnitude.

The most notable asterism is of the water jug itself, tipped and pouring water. This small asterism, which fits nicely into a binocular field of view, is just west of alpha Aquarii and made up of zeta Aqr and three other stars.


Double stars in Aquarius:

Zeta2 Aquarii and zeta1 Aquarii form a binary of two equal white stars with an orbit of 760 years.

Zeta2 Aquarii is the primary: 4.4, 4.6; current PA 266 and separation: 2.3".

Struve 2944 is a nice triple system, with all three in a neat line.

AB: 7.0, 7.5; PA 276, separation 2.5".
C: 8.4; PA 106, separation 50".

The binary is 2 due east of kappa Aquarii.

Struve 2988 is a very attractive pair of equal stars: 7.2, 7.2; PA 101, separation 3.5".

The binary is 3 SW of psi1 Aquarii.

Variable stars in Aquarius:

The most remarkable variable in the constellation is R Aquarii, usually listed as a "Mira variable". Yet this red giant isn't your normal long-period variable; it is a 'symbiotic star', resembling Z Andromedae.

"Z Andromedae" stars are those which show two separate spectra, indicating two quite different temperatures, one cool, the other very hot. This phenomenon is caused by a very close binary system, which the larger star the cooler one, the small star(perhaps a white dwarf) the hot one.

And in fact, R Aquarii has a small blue companion, which is encircled by a gas cloud. When this small star eclipses the giant, the visual magnitude of the primary drops several degrees.

The star has a period of 386.96 days and a range from 5.8 to 12.4; the best time to view this star after the year 2000 is in 2005, in the first week of September.


Deep Sky Objects in Aquarius:

M2 (NGC 7089) is a globular cluster, compact and bright, about 50,000 light years away.

The cluster is 5 N of beta Aquarii.
M72 (NGC 6981 is also a globular cluster, about 3 WSW of the Saturn Nebula (see below). It is one of Messier's least attractive objects.

M73 (NGC 6994) is another uninteresting Messier, a ~ez_lsquo~cluster~ez_rsquo~ comprised of four unrelated stars about 1.5 east of M 72.

NGC 7009, "Saturn Nebula" is a planetary nebula quite spectacular in large instruments. It has ~ez_lsquo~rays~ez_rsquo~ which extend from both sides of the main disc.

The nebula is 1 west of nu Aqr. Burnham (p. 190) has a location chart.
NGC 7293, "Helix Nebula" (or the "Helical Nebula"), is another planetary nebula, given its name apparently because it is said to resemble the DNA double helix. It really is a ring nebula, only much larger and fainter than the more notable Ring Nebula in Lyra.
The nebula is 1.5 W of upsilon Aquarii, or 21 due south of zeta Aquarii.


For a closer appreciation of Aquarius, visit the Binocular Section.


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