Call it a starry roost or celestial aviary, but this week after sunset, five constellations representing exotic or mythical birds flock around the south celestial pole.
Furthest north, and thus visible low on the southern horizon from mid-latitudes in the Northern Hemisphere, are Grus the Crane and Phoenix, the great bird that rose from the ashes of its predecessor. Three other birds lie closer still to the southern pole: Tucana the Toucan, Pavo the Peacock, and Apus the Bird of Paradise. Of these three, only Tucana can be glimpsed from latitude 30° in the Northern Hemisphere.
All five constellations were created by the German celestial cartographer Johann Bayer in 1603,* and only two are mentioned in classical mythology. The peacock figures prominently in the story of Argos, the builder of the ship, Argo, which was used by Jason and the Argonauts in their quest for the golden fleece. When Argos died, Hera changed him into a peacock and placed him in the southern sky not far from his ship.
Pavo is a fairly large and indistinct constellation. Its brightest star (which shines only slightly brighter than magnitude 2), is called the Peacock. The Peacock marks the bird's eye, while Gamma (y), Beta (P), and Delta (8) denote its breast and back. The plumage is set among the stars Lambda (X), Nu (v), Xi ©, Iota (i), Pi (n), and Eta (n), all 4th- and 5th-magnitude stars.
The fabulous Phoenix was said to live for half a millennium. At the end of its life, it settled on a nest made of spices and fragrant leaves. When the Sun was next overhead, the rays ignited the nest, cremating the Phoenix in the flames. From the ashes, however, a new Phoenix arose, wrapped the remains of the dead Phoenix in myrrh, and burned them in the city of Heliopolis as an offering to the Sun. The cyclical metaphor can be traced to ancient China, Egypt, India, and Persia, where the
* In addition, Bayer created six other constellations: Hydrus the Water Snake, Dorado the Swordfish, Volans the Flying Fish, Indus the Indian, Chamaeleon the Chameleon, and Musca the Fly.
Phoenix was an emblem of cyclic patterns and immortality. Ankaa (magnitude 2.3), usually representing the eye of the Phoenix, can be seen just above the southern horizon at latitude 40° north this week around 9 o'clock.
Grus is the Latin name for crane, although to the Spaniards, the constellation of this name was considered a flamingo, which is a different family of bird entirely. Either way, the celestial version has the wing span and long neck of most wading water fowl. This bird's head is usually depicted by Gamma (y) Gruis (magnitude 3). Its right wing stretches out to Iota (i) (magnitude 4) while its left wing is marked by Grus's brightest star, Alnair, (magnitude 1.7), which can just be glimpsed from north latitude 30° southwest of Fomalhaut this time of year.
Southeast of Grus, the pentagonal form of Tucana spans the meridian this week around 7 o'clock. This is not, however, a prominent constellation by any stretch. Its brightest member, Alpha (a) Tucanae, is a little brighter than a magnitude 3 star. The Toucan is perched upon the Small Magellanic Cloud, its eye represented by the blue star Gamma (y) Tucanae (magnitude 4), and its beak by Alpha. The southern bird's tail stretches nearly to the bright star Achernar in Eridanus the River.
Tucana is famous for harboring one of the most spectacular globular clusters in all the sky, 47 Tucanae. This object is bright enough to be seen with the unaided eye as a 4th-magnitude cottony patch of light, and, in fact, often appears plotted as a star in early star maps. It is second only to Omega (ra) Centauri in brightness. A 4- to 6-inch telescope reveals a brilliant, compact ball of tens of thousands of stars.
Just 11° west of the south celestial pole is humble Apus, a dogleg-shaped group of four main stars. Alpha (a), its brightest member, is only magnitude 3.8. Ironically, this unassuming asterism is supposed to represent the beautiful Bird of Paradise, any of the brilliantly colored plumed birds of the New Guinea area. Apus does have one asset, though: the majestic face-on spiral galaxy NGC 2997. Seen in a large backyard telescope, this galaxy is an elongated whirlpool of milky light. Its spiral arms and overall structure are thought to be similar to our own Milky Way galaxy.
Also this week:
• The bright southern star Fomalhaut can be seen due south in the Northern Hemisphere around 9 o'clock. (See September 13 - 19.)
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