- published: 02 Apr 2016
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Lyra ( /ˈlaɪərə/; Latin for lyre, from Greek λύρα) is a small constellation. It is one of 48 listed by the 2nd century astronomer Ptolemy, and is one of the 88 constellations recognized by the International Astronomical Union. Its principal star, Vega (Abhijit in Sanskrit), a corner of the Summer Triangle, is one of the brightest stars in the sky. Beginning at the north, Lyra is bordered by Draco, Hercules, Vulpecula, and Cygnus.
Lyra is visible from the northern hemisphere from spring through autumn, and nearly overhead, in temperate latitudes, during the summer months. From the southern hemisphere, it is visible low in the northern sky during the winter months.
Lyra's brightest stars include the following:
In Lyra are the objects M56, M57, and Kuiper 90. M56 is a rather loose globular cluster at a distance of approximately 32,900 light-years, with a diameter of about 85 light years. Its apparent brightness is 8.3m.
M57, also known as the "Ring Nebula", has a diameter of one light-year and is at a distance of 2,000 light-years from Earth. It is one of the best known planetary nebulae and the second to be discovered; its integrated magnitude is 8.8. Astronomers have determined that it is between 6,000 and 8,000 years old. The outer part of the nebula appears red in photographs because of emission from ionized hydrogen. The middle region is colored green; doubly-ionized oxygen emits greenish-blue light. The hottest region, closest to the central star, appears blue because of emission from helium. The central star itself is a white dwarf with a temperature of 120,000 degrees Kelvin. In telescopes, the nebula appears as a visible ring with a green tinge; it is slightly elliptical because its three dimensional shape is a torus or cylinder seen from a slight angle.