Epsilon Cancri (ε Cancri, abbreviated Epsilon Cnc, ε Cnc) is a white-hued binary star system in the zodiac constellation of Cancer. It is the brightest member of the Beehive Cluster[1] with an apparent visual magnitude of +6.29, which is near the lower limit of visibility with the naked eye. The annual parallax shift of as seen from Earth yields a distance estimate of approximately 606 light-years from the Sun.
The binary pair has the designation WDS J08405+1933. The primary star is designated Epsilon Cancri and the secondary is HD 73711. Epsilon Cancri is itself a spectroscopic binary with components designated Aa (also named Meleph[2]) and Ab. HD 73711 is also suspected of being a spectroscopic binary.[3]
ε Cancri (Latinised to Epsilon Cancri) is the system's Bayer designation, which originally referred to the entire cluster.[4]
In 2016, the IAU organized a Working Group on Star Names (WGSN)[5] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[6] It approved the name Meleph for the component Epsilon Cancri Aa on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.
The system is moving away from the Sun with a radial velocity of +30 km/s.
Epsilon Cancri A is a double-lined spectroscopic binary system with an orbital period of 35.14 days and eccentricity of 0.42. It has a stellar classification of A5 III, which matches an A-type giant star. The spectrum displays the chemically peculiar characteristics of an Am star.[7] Its spectral type has been listed as kA3hA5mF0, indicating the different spectral types shown by spectral lines of calcium, hydrogen, and other metals.[8] Despite the spectral classification, evolutionary models suggest that the star is still on the main sequence, although at the very end of its hydrogen-burning life. The age of the system is estimated to be around 637 million years.
HD 73711 is another Am star, given a stellar classification of F0 III on the basis of its hydrogen absorption lines but a more complete classification of kA3hA5mF0. Although the spectral class would indicate that the star is a giant, models suggest that it is still fusing hydrogen in its core.