The Constellation of Aquarius
...of interesting double stars. It is a beautiful pair of fourth-magnitude stars separated by about 3 arcseconds. The colors of the pair are given as pale green and pale yellow. Another star of note is R-Aquarii, a Mira-type variable star which, over the space of a year, changes from a dim magnitude 11 to a magnitude of six. There are three Messier objects in Aquarius, including M2 and M72, both globular clusters. M2 is one of the better clusters and one which can be visible to a keen-eyed observer on a really dark night. In a small telescope it becomes a ball of faint stars of magnitude 13. M73 is a rather unusual object among those listed by Messier. It is only a small group of stars of similar magnitude that are possibly associated as a multiple-star system. It is also referred to as NGC 6994. First observed in October 1780, M73 was described by Messier as “three or four small stars which look like a nebula at first sight” and contain “a little nebulosity.” Yet no photograph of M73 has ever revealed nebulosity around these stars. The four stars form the shape of a Y, and their magnitudes range from 10.5 to 12.0. Two planetary nebulae take preeminence in a long list of other deep-sky objects in Aquarius. The Saturn Nebula, when seen through a telescope, is a small blue-green dot that Lord Rosse thought looked like a ringed planet.The other, the Helix Nebula, NGC 7293, is the closest planetary nebula to us and occupies an area about half the diameter of the full Moon. This marvelous deep-sky object can be seen in binoculars from dark skies. A cloud of gas and dust ejected from a central star, it resembles a dim smoke ring. Planetary nebulae were named by Sir William Herschel in 1785 because in telescope views they may resemble planets. About a thousand of these shells of stars in their final stages of evolution from giants to dwarfs are known. The central stars are usually blue in color with temperatures up to 400,000K. 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. 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": "The Lucky One of the King") and beta Aquarii ("Sadalsuud": "The Luckiest of Lucky") are twin supergiants with nearly identical names. Gamma Aquarii shares in the good fortune: "Sadachbia": "The Lucky Star of Hidden Things". One question often brought up, "Why is all that luck portrayed in this constellation". 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. Aquarius, later came to be identified with Ganymede, a beautiful young shepherd who was abducted by Zeus and taken to Mount Olympus to be the cup bearer to the gods. (The constellation Crater, is sometimes identified as Ganymede's cup.) The constellation Aquarius was named by the Sumerians after their god of heaven An, who pours the waters of immortality upon the earth. Aquarius also figures in a ...