M 57: The Ring Nebula
A Little on Lyra
The constellation Lyra is rather small and faint from the city but it is easy to find due to being home to Vega, the 5th brightest star in the northern hemisphere. Interestingly, around 12,000 years ago, Vega (Alpha Lyrae) served as the Pole star and will again if mankind can survive another 12,000 years.
Strummed like a guitar rather than plucked like a harp, the lyre is an ancient stringed instrument dating back to around 3,000BCE. According to ancient Greek mythology, Hemes, the son of Zeus, invented the lyre by stealing a sacred cow from his half-brother Apollo and stringing the cow's intestines across a tortoise shell. Evidently, Apollo wasn't too happy with the act but forgave his half-brother in return for the instrument.
Sometime later, Apollo gave the lyre to Orpheus who became a master of the lyre, enrapturing not only his fellows and the gods of nature but even Hades himself, the dark lord of the underworld. Orpheus met his own violent end when female followers of Dionysus tore him apart limb from limb but in remembrance of this musical genius, Apollo convinced his father Zeus that the instrument played so majestically by Orpheus should become a heavenly constellation and thus, the lyre of Orpheus rests now between Hercules and Cygnus.
A Little on M 57
Placed between the exquiste multiple binary star Beta Lyrae (Sheliak - The Tortoise) and Gamma Lyrae (Sulafat - The Shell) is M 57, a small but perfect smoke ring structure. It is about 2,300 light years away from us and was probably created when a red giant ran out of fuel to burn and its shell of gas, which could no longer be gravitationally held to the dying star, was blown away, pushed outward by hot and fast stellar winds from the red giant.
M 57 is known is a planetary nebula, not because it has anything to do with planets, but because William Herschel, a great astronomer from the late eighteenth century, saw these nebulae, these great spherical clouds round like the planets. M 57's outer layer of gas is about 2 to 3 light years in diameter whilst its darker core is about 1 light year across. It is estimated that this outer ring, that halo we see, expands at about 50 km/s which I imagine from Earth would look like its growing about an inch every century, and all this nebula activity probably began some 10,000 years ago. Today, all that's left of that original red giant is a dense, white dwarf star, the final evolutionary state for a star whose mass was never high enough to become a neutron star.
In my 4" refractor from a city roof top, M 57 looks as if some cosmic wonder has puffed a single smoke ring into the heavens. The halo offers the curious affect of a solid ring of misty light whilst its interior, that central vacuity, black like deep space. Nevertheless, if you remain with M 57 for a while, if you give yourself time, it soon becomes apparent that it is not ring like in shape but oval, tilted from northwest to southeast from its centre and that its central core begins to take on the appearance of feebler, lighter kind of absolute darkness.