Home Page

Valley Skies

Newsletter Home Page

Constellations:
Lyra the Lyre

Gen: Lyrae
Abb: Lyr
Dec: +25.6° to +47.7°
RA:  18h 12m to 19h 26m
Area: 286 sq. deg.

Lyra is Latin for lyre, a stringed musical instrument. Although Lyra is a small constellation, it is very easy to locate. Look for Lyra’s brightest star Vega located between the constellations Cygnus and Hercules. Vega is the fifth brightest star in the night sky as well as being the westernmost star in the Summer Triangle. Once you locate Vega, the rest of the constellation consists primarily of four stars that form a parallelogram to the south of Vega.

Vega lies on an imaginary circle that is traced by the Earth’s axis as it slowly changes alignment with respect to the stars. This phenomenon is known as precession, and it takes approximately 26,000 years to complete one full cycle. If you look at the picture below you can see how Vega will become the North Star in about 12,000 years.

Now if we go back in time about 14,000 years we would find that Vega was at that time aligned with the Earth’s axis. This time frame was also the dawn of civilization in the Middle East. With Vega as the North Star, Lyra would rotate around the pole like the big and little dippers do today. With this in mind it is easy to see that this group of stars has been viewed for so many years that it may be one of the oldest asterisms to be used by man.

With a past as long as this, the constellation has been known by many names and descriptions, most of which have been lost with the sands of time. The name we use today comes from the Greeks and describes a lyre or harp that was invented by Hermes, the son of Zeus and Maia. As the story goes, Hermes at a very young age stole a herd of cattle from the god Apollo and ran away to the island of Cyllene. One day on the island Hermes also found a turtle that he killed. He later cleaned the shell and stretched strips of cow gut across the opening to make a lyre. When Apollo finally found his stolen cattle he also found Hermes’s lyre. Apollo was so impressed with the music from the lyre that he worked out a trade to get it. Apollo later gave the lyre to his son-in-law Orpheus to take aboard the Argo during Jason’s quest for the Golden Fleece. On the quest Orpheus used the lyre to drown out the songs of the sirens and saved the crew. Years later Orpheus was killed and the lyre was placed into the sky.

Exploring in Lyra

For this month we have one of the best planetary nebulae, a small globular cluster and a wealth of double stars to look at.

Start at Vega (3 Alpha Lyrae), a blue-white star that is magnitude 0.03. (Try not to look at Vega in your telescope if you hope to find any deep sky objects for the next hour or so.)

Vega is special in several ways, not only because it was the pole star as stated above. It is also the MK spectrum standard for AO V main-sequence stars as well as the standard that is used to calibrate the equipment that measures magnitudes of stars and other objects in space. Vega sits at a point in the sky called the "Apex of the Sun’s Way," the direction toward which our sun and solar system are traveling, at a rate of 19 km/s.

At one time Vega was thought to be the primary star of a wide multiple system, but more recent studies have shown that Vega is moving away from the other stars. One last bit of information on Vega is that it holds the distinct honor of being the very first star to be photographed, in July 1850 by William Cranch Bond.

Move about 1½° to the northeast of Vega to find Epsilon1 and Epsilon2 Lyrae also known as the Double-Double. This system was first discovered by Sir William Herschel in 1779 and is a really good sight in a telescope. The two primary stars do not appear to have any orbital motion so they are only a visual double and not a true binary system.

Travel south 2° to our next multiple system 6 Zeta Lyrae and 7 Zeta Lyrae. The main stars are easy to separate but the other stars in the system get lost in the glare.

Hop down to Lyra’s southwestern corner to Sheliak (b Lyrae). Sheliak comes from the Arabic Al Shilyak and means the Tortoise (remember the story about Hermes). Sheliak is a bright eclipsing binary that you can watch change from magnitude 3.34 to 4.34 over a 12.9-day period. There is a lot of debate over what is happening with these two stars. The rapid rotation of the secondary star around the primary is causing both stars to distort in shape. One theory is that matter is being pulled from the primary star to the smaller secondary star at a tremendous rate.

Next move your scope to the area mid-way between b and g Lyrae. Here you will find M57 -- probably the easiest planetary nebula to find, as well as one of the brightest in the sky. M57 is NGC 6720, but it is most often referred to as the "Ring Nebula." The Ring Nebula was first discovered in early January 1779 by Antoine Darquier de Pellepoix. He described it as being "an oval nebulous object appearing to be about the same size as Jupiter." Messier found it later in the same month and logged it as the 57th object on his list. This planetary has a bluish-green shell of gas around a 14.8 magnitude star that is extremely dense and hot.

To the east of the Ring Nebula is Sulafat (g Lyrae) at magnitude 3.24. You can use this star to compare the brightness of Sheliak.

For our last hop in Lyra, move to a point just over half way between Sulafat and Albireo in Cygnus. This is an area dense in stars so you will have to look close to find a small fuzzy patch among the other stars in the area. This fuzzy patch is the class 10 globular cluster M56 (NGC 6779) and looks like a small tight knot of stars.

This concludes the tour of Lyra for this month, but while you are in the area I recommend continuing on to Albireo. Albireo is probably the most famous color contrasting double star in the sky, with a very gold primary and a deep blue "B" star, a great sight to end the night.

Happy Star Hopping...Eric

Copyrighted © 2000 by Stockton Astronomical Society
Lasted Updated: 11/20/2000
http://www.stocktonastro.org/Newsletter/CON_Lyra.html