Jimmy Westlake: Look east for heaven’s little harp
What’s that bright star rising in the northeastern sky as darkness falls this month? It’s the star Vega, and its arrival is a sure sign that summer is just around the bend.
Vega marks one corner of our well-known asterism called the Summer Triangle and is the first corner of the triangle to pop up above the horizon. It is the alpha star in a constellation named Lyra, the Harp.
The name Vega is derived from some Arabic words that mean “the falling vulture,” so named because it marks the head of a vulture, holding the heavenly harp in his beak. Lyra represents a magical harp, made from an empty tortoise shell by the famous mythological musician Orpheus.
In addition to the flashy star Vega, this constellation includes a small but distinctive parallelogram of four stars that represents the strings of the harp. It dangles just below Vega as it rises in the northeastern sky after dusk.
Lyra is a tiny, compact constellation and is easy to spot, primarily because of brilliant Vega. Astronomers have determined that Vega rotates with its axis pointed almost directly at the Earth and sun, which means that our sun might be the pole star as seen from some Vegan planet, just as Polaris appears to be the North Star from Earth.
Vega is also the brightest star that can ever be our north polar star. Around the year 12,000 AD, the Earth’s axis will have shifted away from Polaris and will point toward Vega.
Although Vega might be Lyra’s main claim to fame, there are many others.
The star marking the bottom right corner of the parallelogram of strings 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 best known 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, Messier 57, or M57 for short. The Ring Nebula was formed thousands of years ago when a dying red giant star blew away its outer layers. The expanding shells of gas create the glowing ring around the dead star. It looks like a ghostly little 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 “double-double” star, Epsilon Lyrae. A keen eye can manage to split the two main stars without optical aid, but a telescope reveals that each of those is again double — a beautiful quadruple star system.
There’s a lot to see and enjoy in this tiny constellation of summer, Lyra, Heaven’s Little Harp.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper and his “Cosmic Moment” radio spots can be heard on local radio station KFMU. Check out Jimmy’s astrophotography website at http://www.jwestlake.com.
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