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Lyra the Heavenly Harp
Many people know of Orpheus, the musician of legend who could charm even wild animals with his songs. But not so many know that you can find his favorite instrument, the lyre or harp, in the sky. It's the constellation Lyra, and in the northern hemisphere it lies almost overhead on summer evenings.
Although Lyra is small, it's easy to find because its leading star is Vega, one of the brightest stars in the entire sky. Vega, 25 light years away, shines like a blue-white diamond in the skies of summer. It's the brightest member of the so-called Summer Triangle of stars, which also includes Deneb in the constellation Cygnus, the swan, and Altair in Aquila, the eagle.
If you saw the movie Contact, starring Jodie Foster as a radio astronomer who makes contact with aliens, or read Carl Sagan's book on which the film is based, you may know that Vega is the star she goes to.
Orpheus and Eurydice
In the Greek myth, Orpheus descended into the Underworld to plead for the release of his beloved wife Eurydice who had died tragically from a snakebite. Even cold-hearted Hades, the god of the Underworld, was so charmed by Orpheus’s music that he agreed to let Eurydice go. But only on condition that Orpheus must not look behind him until the couple reached the surface.
Strumming his lyre to guide her, Orpheus led Eurydice from the darkness of Hades to the upper world. When they were nearly there, he couldn't resist glancing behind him to confirm Eurydice was really following – that broke the condition and Hades snatched her back.
Thereafter Orpheus wandered the countryside, playing mournfully. Other women offered themselves to him, but he rejected them all. Eventually they ganged up and killed him. Orpheus joined his beloved Eurydice in the Underworld, while his lyre was placed among the stars as the constellation Lyra.
Stars of Lyra
Look at Vega through binoculars and you will see a wide double star near it, like a pair of cat’s eyes. This is known as Epsilon Lyrae. A small telescope with high magnification divides each of the stars into a much closer pair, so Epsilon Lyrae is in fact a family of four stars, all linked by gravity. It's popularly termed the “Double Double” and is regarded as the finest quadruple star in the sky.
Four other stars in Lyra form a box shape. One of them is Delta Lyrae, an even wider double than Epsilon Lyrae. In this case, though, the two stars are at different distances from us and appear near each other only because of a chance alignment. Such an arrangement is known as an optical double, whereas stars that are linked by gravity are known as a binary.
At the opposite corner of the box from Delta Lyrae is another fascinating multiple star, Beta Lyrae, also known as Sheliak. Through a small telescope it appears as an attractive double of cream and blue stars. The brighter star – the cream-colored one – is what’s known as an eclipsing binary, meaning that it consists of two very close stars that eclipse each other as they orbit. In this case, the brightness dips every six and a half days as one star passes in front of the other. Although the two stars are so close that we can’t see them separately, astronomers have deduced that their mutual pull of gravity distorts them into egg shapes.
Midway between Beta and Gamma Lyrae lies a colorful donut. It’s the Ring Nebula, also known as M57 from its number in the catalog of fuzzy objects compiled by the French astronomer Charles Messier.
The Ring Nebula is what’s known as a planetary nebula, a shell of gas thrown off by an aging star after it swells up into a red giant and loses its outer layers. The colors indicate different temperatures, with the hottest gas near the center and the coolest farthest out. Unfortunately, you won’t see the colors in a backyard telescope.
Through the gauzy gas at the middle of the ring you can just spot a tiny dot, which is the core of the former giant star. It's the type of star known as a white dwarf, which is only about the size of the Earth, but is very hot and dense. Astronomers predict that our own Sun will end its life as a shrunken white dwarf surrounded by a planetary nebula. So when we look at the Ring Nebula, we are seeing a preview of the death of our own star billions of years from now.
Content copyright © 2013 by Mona Evans. All rights reserved.
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