Eta Lupi

η Lupi, often Latinised as Eta Lupi, is a probable triple star^[4][12] system in the southern constellation of Lupus. It is visible to the naked eye with an apparent visual magnitude of 3.41.^[2] Based upon an annual parallax shift of 27.80^[1] mas as seen from Earth, it is located around 136 parsecs (440 ly) distant from the Sun. It is a member of the Upper Centaurus–Lupus subgroup of the nearby Sco OB2 association.^[13]

The inner pair in this triple system has an estimated orbital period of around 27,000 years.^[12] As of 2013, they had an angular separation of 15.0 arc seconds along a position angle of 19°.^[3] The primary star, component A, is an evolving A-type subgiant star with a stellar classification of B2 IV.^[4] It has used up the supply of hydrogen at its core and has begun to expand off the main-sequence.

The secondary, component B, is a chemically peculiar A-type main sequence star with a class of A5 Vp^[4] and an estimated mass 2.10 times that of the Sun.^[12] The outer member, component C, has an orbital period of around half a million years.^[12] As of 2007, it had an angular separation of 115.8 arc seconds along a position angle of 248° from the primary.^[3] It is an F-type main sequence star with a classification of F5 V and an estimated 1.29 times the Sun's mass.^[12]