Celestial News: Lyra — Heaven’s little harp
For Steamboat Pilot & Today
Shining down on us in the early evenings this month from high up overhead is the fifth brightest star visible from Earth, a star named Vega. Vega anchors the brightest corner of the well-known asterism called the Summer Triangle. The three corners of the Summer Triangle are marked by stars Vega, Deneb and Altair.
Vega is also the alpha star in the official constellation named Lyra, the harp, and shines only 25 light years from Earth. The name Vega loosely translates from Arabic into “the falling vulture,” so named because it represents the head of a vulture holding the heavenly harp in his beak.
Lyra represents the magical harp that the mythological musician Orpheus made from an empty tortoise shell. In addition to the flashy star Vega, this constellation includes a small but distinctive parallelogram of four stars that dangles just below Vega and represents the strings of the harp. Lyra is a tiny, compact constellation and is easy to identify, primarily because of its showpiece Vega.
Astronomers have determined that Vega rotates with its axis pointed almost directly at the Earth and Sun, which means that our Sun might serve as the pole star for some Vegan planet, just as Polaris happens to be the pole star as viewed from 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. So, if you look up one night and think Sheliak looks a little fainter than usual … chances are, it does.
Not far from Sheliak is the famous Ring Nebula, also known by its catalogue number, Messier 57, or M57 for short. 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 shells of gas continue to expand away from the star, forming what looks like a ghostly little smoke ring in the sky. This same fate awaits our Sun when it balloons into a red giant giga-years from now. A small telescope is required to spot the Ring Nebula, about midway between the stars Sheliak and Sulafat.
Right beside Vega, you can spot the famous “double-double” star, Epsilon Lyrae. A keen eye can manage to split the two main stars without any optical aid, but a telescope reveals that each of those stars is again double — a double-double star.
There’s a lot to see and enjoy in this tiny constellation of late summer, Lyra, heaven’s little harp.
Jimmy Westlake is the former fulltime professor of physical sciences at Colorado Mountain College’ Steamboat Springs and former director of the Rollins Planetarium at Young Harris College. His “Celestial News” column appears monthly in the Steamboat Pilot & Today. Westlake’s astrophotography website can be found at jwestlake.com.
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