The Equuleus Constellation

Equuleus is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy and remains one of the 88 modern constellations. Its name is Latin for ‘little horse,’ a foal. It was It is the second smallest of the modern constellations (after Crux), spanning only 72 square degrees. It is also very faint, having no stars brighter than the fourth magnitude.

The brightest star in Equuleus is Alpha Equulei, traditionally called Kitalpha, a yellow star magnitude 3.9, 186 light-years from Earth. Its traditional name means “the section of the horse.” There are few variable stars in Equuleus. Only around 25 are known, most of which are faint. Gamma Equulei is an alpha CVn star, ranging between magnitudes 4.58 and 4.77 over a period of around 12½ minutes. It is a white star 115 light-years from Earth and has an optical companion of magnitude 6.1, 6 Equulei. It is divisible in binoculars. R Equulei is a Mira variable that ranges between magnitudes 8.0 and 15.7 over nearly 261 days.

Equuleus contains some double stars of interest. γ Equ consists of a primary star with a magnitude around 4.7 (slightly variable) and a secondary star of magnitude 11.6, separated by 2 arcseconds. Epsilon Equulei is a triple star also designated 1 Equulei. The system, 197 light-years away, has a primary of magnitude 5.4 that is itself a binary star; its components are of magnitude 6.0 and 6.3 and have a period of 101 years. The secondary is of magnitude 7.4. δ Equ is a binary star with an orbital period of 5.7 years, which at one time was the shortest known orbital period for an optical binary. The two components of the system are never more than 0.35 arcseconds apart.

Due to its small size and its distance from the plane of the Milky Way, Equuleus contains no notable deep sky objects. Some very faint galaxies between magnitudes 13 and 15 include NGC 7015, NGC 7040, NGC 7045 and NGC 7046. Credit: Wikipedia.