Summer Triangle
An asterism, formed by the bright stars Vega in Lyra, Deneb in Cygnus, and Altair in Aquila, which lies high overhead on summer and early autumn evenings at mid-northern latitudes. All three of these white stars have similar surface temperatures, Vega, at 9,500 K, the warmest. Though Vega and Altair are really quite luminous, they are first magnitude primarily because they are close to us, averaging only 25 light-years away, while Deneb is an extraordinarily luminous star at a distance of some 2,500 light-years.
Related category
• OBSERVATIONAL ASTRONOMY
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