The night sky is full of birds. Here are some of them.
Cygnus the swan
My favorite is Cygnus, a beautiful northern constellation and one of the few whose pattern resembles what it represents: a swan with outstretched wings. The head is down and the star Deneb is its tail. The five brightest stars form the well known asterism of the Northern Cross. An asterism is a pattern of stars that isn't a constellation. Deneb is also one corner of the asterism called the Summer Triangle, although it's visible for most of the year.
Sometimes I see swans flying low along the Thames. Many birds use the river as a highway. Cygnus reminds me of this as it flies along the Milky Way – its bright stars make it recognizable even in the city.
The constellation was already ancient when Ptolemy described it in the Almagest in the second century. The most famous story associated with it is the seduction of Leda the queen of Sparta by the god Zeus (Jupiter to the Romans) in the guise of a swan.
Aquila the eagle
Aquila is the eagle who carried Zeus's thunderbolts of Zeus and occasionally aided the god in his seductions. Like Cygnus, Aquila is an ancient constellation described by Ptolemy. Its brightest star Altair (flying bird) is a second corner of the Summer Triangle and interestingly, the third corner is also a bird, Vega in the constellation Lyra (the harp). The Arabs knew Vega as a swooping eagle, and its Latin name meant vulture. Bode represented Lyra in his Uranographia with Vega as a bird.
Just below the eagle's tail in neighboring Scutum is the Wild Duck Cluster (Messier object M11). To an early observer it resembled the V of a flight of wild ducks, though this feature tends not to show up in photographs. It's an open star cluster like the Pleiades, but about thirteen times farther away. First magnitude stars are very bright ones and this cluster contains hundreds of them – it would be a dazzling sight if it were closer.
Southern constellations by Petrus Plancius
The south polar region was unknown to northern astronomers, so instead of constellations of antiquity, they are inventions from the late 16th century onwards. Dutch astronomer Petrus Plancius used observations by Pieter Dirkszoon Keyser and Frederick de Houtman to invent a dozen new ones. Unlike traditional constellations, the Plancius constellations have few named stars and lack associated myths.
Plancius seemed inspired by natural history in his choices, six of which represented birds. He put the constellations on a celestial globe, but their first appearance in print was in Johann Bayer's Uranometria (1603). Here's how Bayer depicted Apus, Pavo, Tucana, Grus and Phoenix.
Apus is the bird of paradise, a name coming from a Greek word meaning “footless”. It wasn't until the 19th century that a European saw a live bird of paradise, but traders had the preserved skins and plumes without feet or wings. It was a common belief that the birds had no feet, but spent their lives afloat in the air held up by their plumes.
Although Pavo was unknown to the Greeks, the peacock echoes Greek mythology. Peacocks drew the chariot of the goddess Hera (wife of Zeus). Pavo's neighbor Grus is a crane, though that's not obvious from Bayer's drawing. Grus was formed out of the traditional constellation Piscis Notius, and some of the stars have Arabic names.
Tucana (the toucan) is a fairly undistinguished constellation, notable because it contains the Small Magellanic Cloud. This isn't a cloud, but a small companion galaxy to the Milky Way. The Phoenix is well known as the legendary bird which lived for 500 years before being consumed by fire, then resurrected from the ashes as a young bird.
European explorers invented southern constellations without reference to local star lore. A prominent indigenous constellation is the Australian aboriginal Emu (related to the ostrich). Their sky patterns weren't based solely on stars. The emu in the sky relies substantially on dark nebulae.
A classic image from the Hubble Space Telescope is the Pillars of Creation of the Eagle Nebula in the constellation Serpens. The “pillars” are enormous clouds of gas and dust, the largest of them seven light years long. Within them stars are being formed.
Corvus (crow or raven) is a constellation described by Ptolemy. Although it has eleven stars theoretically visible with the unaided eye, Ptolemy mentioned only seven. It contains a planetary nebula NGC 4361, which is beautifully spherical with the dying star in the center. As the star shrinks and cools, it sloughs off its outer atmosphere to form the nebula.
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