Jimmy Westlake: The heavenly harp


Jimmy Westlake

Jimmy Westlake's Celestial News column appears monthly in the Steamboat Today.

Find more columns by Westlake here.

What's that bright star rising in the northeastern sky as darkness falls this month? It's Vega, and its arrival is a sure sign that summer is just around the corner. Speaking of corners, Vega marks one corner of the well-known asterism called the Summer Triangle and is the first corner of the triangle to pop up above the horizon.

Vega is the brightest star in the constellation named Lyra the Harp. The name Vega literally means "the plunging vulture," so named because it marks the head of a vulture holding the heavenly harp in its beak. Lyra represents the harp made from an empty tortoise shell by the famous mythological musician Orpheus. In addition to the brilliant star Vega, this constellation includes a small parallelogram of four stars representing the strings of the harp, dangling below Vega as it rises in the northeast.

Lyra is a tiny, compact constellation and is easy to identify, primarily because of Vega. Astronomers have determined that Vega rotates with its axis pointed almost directly at our sun, which means that our sun might be the pole star as seen from some Vegan planet, just as Polaris happens to be the north pole star for Earth.

Brilliant Vega might be Lyra's main claim to fame, but there are many others.

The star marking the bottom right corner of the parallelogram is an unusual binary star named Sheliak. By chance alignment, once every 13 days Sheliak's fainter star eclipses its brighter star, causing it to suddenly drop to one-half its normal brightness. Sheliak is one of the finest eclipsing binaries in the sky, and its variations in light can be followed with the unaided eye.

Not far from Sheliak is the famous Ring Nebula, also known by its catalogue number M57. Often pictured in textbooks as the best example of a planetary nebula, the Ring Nebula was formed when a dying red giant star blew away its outer layers. The shell of gas continues to expand away from the star, forming what looks like a ghostly smoke ring in the sky. A small telescope is required to spot the Ring Nebula, and its exact location can be found on any good star chart.

Right beside Vega is the famous quadruple star Epsilon Lyrae. The unaided eye can barely split the two main stars, but a telescope reveals that each of those also is double.

There's a lot to see and enjoy in this tiny constellation of summer, Lyra the Harp.

Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published on the Web sites of CNN.com, NASA's "Astronomy Picture of the Day," Spaceweather.com, Space.com, Discover.com, and in Sky & Telescope, Astronomy, Night Sky, Discover, and WeatherWise magazines.


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