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Lyra:
The Harp of Heaven
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For a little constellation, Lyra has
big ideas! It has the commanding star of the summer sky, Vega,
fifth brightest of all stars. It has a wondrous deep-sky object,
M57, the Ring Nebula. It has its own meteor shower, the Lyrids
which can be observed between April 20-22 each year. It has its
own class of variable star, called the RR Lyrae stars. And Lyra
is also the location for another fascinating variable, b Lyrae,
a mysterious system that is an eclipsing binary with a possible
black hole as one of its components. Epsilon Lyrae is a favorite
telescopic object. It is the “double-double,” discernible
to those with exceptional eyesight as a pair of stars; and with
a small telescope, each can be resolved into a double, as well.
A lesser pair of double stars also shines in Lyra, although the
components are not quite so bright nor so closely spaced. They
are S 2470 and S 2474.
Lyra is a small constellation, quite easily identified as it
appears to consist of an equilateral triangle attached to a parallelogram.
The brightest star, Vega, is one of the three stars, along with
Deneb and Altair, that form the asterism of the Summer Triangle.
Photo by Conrad Jung.
The
wonderful Ring Nebula, M57, can be found between Gamma- and Beta-Lyra,
the two stars that form the side of the parallelogram opposite
Vega.
Because of their circular appearance such rings are also called
planetary nebula. They are very large, as much as a thousand times
as large as our solar system. The very hot central star is responsible
for the luminescence of the nebula.
Photo by Jim Scala
Lyra is also prominent in the history
of astronomy. Vega was the first star to pose for its photograph,
taken by Bond and Whipple a hundred-fifty years ago on July 16,
1850, at Harvard College Observatory. Vega was also among the
first stars whose parallax was accurately determined, by F. G.
Wilhelm Struve, father of the noted Otto Struve. Vega's role in
future history is assured, as well, for it has been calculated
that in something like 12,000 years, owing to precession of the
equinoxes, Vega will assume the title of North Star.
Incidentally, the name Vega is properly pronounced as if it were
spelled Wega, for it derives from the Arabic, meaning “Swooping
Eagle of the Desert.”
Classical mythology links the lyre and the tortoise in the story
of Mercury, who found a tortoise shell and toyed with it. He noticed
the resonance when he tapped the shell, which gave him the idea
to drill holes along opposite sides and lace these with linen
threads. He used one each for the nine Muses. So was the lyre
invented; and Mercury played enchanting music. On Olympus, home
of the gods, Apollo beseeched Mercury to teach him also to play,
and Mercury traded the lyre to Apollo for his caduceus, the staff
that brought prosperity and wealth to its owner and gave him the
power to fly. Mercury then became the swift messenger of the gods,
enabled by the caduceus and his winged sandals. Apollo later gave
the lyre to his son, Orpheus, who learned to play with such talent
that he would soothe the wild beasts. He could charm even Pluto,
king of the realm of the dead. But that is another story.
After the death of Orpheus (in that other story), Jupiter placed
the lyre in the heavens, where it is high overhead, a jewel in
the summer evening skies.