Eta Muscae is a multiple[9][10]star system in the southern constellation of Musca. It is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude of 4.79.[3] The system is located around 406 light years away from the Sun.[6] It is a member of the Lower Centaurs Crux subgroup of the Sco OB2 stellar association of co-moving stars.[11]
The two main components of this system form a double-lined spectroscopic binary[12] with a period of 2.4 days in a circular orbit.[7][11] They are a detached eclipsing binary with a spectral type of B8V and a brightness that dips by 0.05 magnitude once per orbit.[13] This pair consists of two components of similar mass and type.[4]
Further away from the primary system are stars of magnitude 7.3 and 10, designated Eta Muscae B and C. It is unclear if these stars are gravitationally–bound to the main pair. Evidence for an additional component has been found with a 30-year cycle in the orbital behavior of the main pair.[9] The data suggests an orbital eccentricity of 0.29 for this suspected component, Eta Muscae D.[14]
^Hube, Douglas P. (1970). "The radial velocities of 335 late B-type stars". Memoirs of the Royal Astronomical Society. 72: 233. Bibcode:1970MmRAS..72..233H.
^Medici, A.; Hubrig, S. (January 2000). "Triple System epsilon Vol and Quadruple System eta Mus: the Mass Ratio in Close Binary Systems". Information Bulletin on Variable Stars. 4827: 1. Bibcode:2000IBVS.4827....1M.
^ abHensberge, H.; et al. (April 5–10, 2003). Lépine, Jacques; Gregorio-Hetem, Jane (eds.). η Muscae: a multiple system with a PMS component. Open Issues in Local Star Formation. Proceedings of the Ouro Preto Colloquium, Brazil. Astrophysics and Space Science Library. Vol. 299. Kluwer Academic Publishers, Dordrecht. Bibcode:2003ASSL..299P...8H.
^Blackford, M. G.; et al. (June 2016). "The AD binary in the multiple system eta Mus". Information Bulletin on Variable Stars. 6171: 1. Bibcode:2016IBVS.6171....1B.