Astrophoto: The Iris Nebula by Tom Davis
Written by R. Jay Gabany
Our home galaxy, the Milky Way, is estimated to have 400 billion stars, give or take 200 billion, but less than 6,000 (also an estimate) are visible from dark locations without telescopic aide- and only part of this number can be seen during any single night. Some are dim but close, others are bright but remote and many are partially hidden behind veils of dust so their splendor only hints at their distance. Therefore, the placement of the stars and their brilliance in the sky creates a completely random distribution of bright pinpoints overhead that people have, nonetheless, grouped into familiar patterns called constellations. This affinity for recognizing or imagining designs also extends to the objects in space that can only be seen through telescopes or in photos with long exposures such as this article's featured picture that, many believe, resembles a flower.
Humans are pattern seeking, storytelling beings. It is almost impossible for us to look out at nature and not find some sort of pattern that can spawn a tale. That's what myths and stories are all about- giving some meaning to an identifiable arrangement. Almost all ancient cultures, regardless of their location, grouped the stars into designs that reminded them of their mythology, animals or everyday objects. For example, as far back as 6,000 years ago, cuneiform texts found in the valley of the Euphrates River described a lion, a bull, and a scorpion in the sky. Orion, the constellation of the hunter, has a history dating even earlier than 4,000 BC. However, many civilizations in antiquity saw different sets of objects. The ancient Chinese, the Babylonians, the Mayans and the Aztecs each populated the skies with visions rooted in the beliefs and priorities of their cultures. Similar patterns tended to overlap- such as the constellation Capricornus, for example. The ancient Aztecs interpreted the constellation as a whale; the Indians saw an antelope; the Assyrians called it a goatfish while the ancient Greeks said it was a gate for the gods.
Many of our constellations are handed down from the ancient Greeks who probably adopted them from the Babylonians and Sumerians. More than a few modern designations are based on a list compiled by the Roman astronomer, Claudius Ptolemy, who lived in Alexandria, Egypt. He grouped over one thousand stars into forty-eight constellations during the second century A.D. His compilation, called The Almagest, formed the basis for the modern list of eighty-eight constellations officially designated by the International Astronomical Union (IAU) in 1930.
Today, twenty-nine objects, nineteen land animals, fourteen men and women, ten sea creatures, nine birds, two insects, two centaurs plus a serpent, a dragon, a flying horse, a river and even a head of hair have been placed into the night sky. The IAU also extended the boundaries for each constellation so that every part of the firmament fell within a designated star grouping. From an astronomer's perspective, constellations are a method of referencing a defined piece of the real estate above.
But, Ptolemy did not discover the constellations. No one did. They were most likely invented by farmers who needed to recognize the seasons for planting and reaping and by hunters as a way to avoid becoming lost when pursuing game on extended hunting forays. The human mind has an affinity for detecting patterns out of apparent chaos. This adaptation is the result of our evolution- it enabled us to find food, recognize friends from enemies and, in short, to survive as a species. The constellations, therefore, are a mnemonic, or memory device, that enables us to break the night sky into chunks that can be more easily recognized.
Our natural ability to connect dots together is also being heavily researched by the security industry and law enforcement agencies in an effort to devise a method that will enable computers to recognize facial patterns of criminals and terrorists. This technology holds much promise although, to date, it has not been proven effective. At the same time, it has attracted a host of critics who are concerned about personal privacy and civil liberties.
Interestingly, the image that accompanies this article of NGC 7023, located in the northern constellation of Cepheus, gained its common name only relatively recently. Astronomer Tony Hallas tells a story that occurred several years ago, before digital photography replaced film, when his wife and fellow astronomer, Daphne, saw a (then) new enhanced color film version of this nebula and exclaimed that it reminded her of an Iris! That event may have become all but forgotten to many but the name has remained as others confirmed Daphne's association between the shape and colors of this star forming region and the delicate petals of a newly opened spring flower.
Other deep space objects also remind people of familiar things and places such as the North American Nebula, featured here earlier this summer.
The brilliant star near the center of this picture is young, very hot and, in relative terms, was only recently created. The cloud from which it formed still surrounds this young Sun but is being blown away by the push of star's massive radiation. This beautiful new picture, taken by Tom Davis, shows the way it looked 1,300 years ago due to the distance that separates it from Earth and the speed that light travels.
Tom produced this image from his private observatory in Inkom, Idaho using a 10-inch telescope and an 11 mega-pixel astronomical camera. The total exposure required almost six hours.
Do you have photos you'd like to share? Post them to the Universe Today astrophotography forum or email them, and we might feature one in Universe Today.
Written by R. Jay GaBany
Filed under: Astrophotos
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