and 108 stars in total are brighter than magnitude 6.5, the traditional limit for naked-eye visibility. Serpens Caput's boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a 10-sided polygon, while Serpens Cauda's are defined by a 22-sided polygon. In the equatorial coordinate system, the right ascension coordinates of Serpens Caput's borders lie between and , while the declination coordinates are between and . Serpens Cauda's boundaries lie between right ascensions of and and declinations of and . The International Astronomical Union (IAU) adopted the three-letter abbreviation "Ser" for the constellation in 1922. Features Stars Head stars Marking the heart of the serpent is the constellation's brightest star, Alpha Serpentis. Traditionally called Unukalhai, is a red giant of spectral type K2III located approximately 23 parsecs distant with a visual magnitude of 2.630 ± 0.009, meaning it can easily be seen with the naked eye even in areas with substantial light pollution. A faint companion is in orbit around the red giant star, although it is not visible to the naked eye. Situated near Alpha is Lambda Serpentis, a magnitude 4.42 ± 0.05 star rather similar to the Sun positioned only 12 parsecs away. It has an exoplanet orbiting around it. Another solar analog in Serpens is the primary of Psi Serpentis, a binary star located slightly further away at approximately 14 parsecs. Beta, Gamma, and Iota Serpentis form a distinctive triangular shape marking the head of the snake, with Kappa Serpentis (the proper name is Gudja) being roughly midway between Gamma and Iota. The brightest of the four with an apparent magnitude of roughly 3.67, Beta Serpentis is a white main-sequence star roughly 160 parsecs distant. It is likely that a nearby 10th-magnitude star is physically associated with Beta, although it is not certain. The Mira variable R Serpentis, situated between Beta and Gamma, is visible to the naked eye at its maximum of 5th-magnitude, but, typical of Mira variables, it can fade to below magnitude 14. Gamma Serpentis itself is an F-type subgiant located only 11 parsecs distant and thus is quite bright, being of magnitude 3.84 ± 0.05. The star is known to show solar-like oscillations. Iota Serpentis is a binary star system. Delta Serpentis, forming part of the body of the snake between the heart and the head, is a multiple star system positioned around 70 parsecs from Earth. Consisting of four stars,