EZ Aquarii - Luyten 789-6 ABC

Luyten 789-6, also known as EZ Aquarii, is a triple star system approximately 11.3 light years from the Sun. It appears in the eastern part of the constellation Aquarius. All three of its components are red dwarfs, and the main component is a spectroscopic binary. Its nearest neighboring star is Lacaille 9352, about 4.21 light years away.

Luyten 789-6 was discovered by Willem Jacob Luyten, who measured the proper motions of over 520,000 stars by building an automated photographic plate scanner. With a combined apparent magnitude of +12.87, all three components are too faint to be seen with the naked eye. All three stars are red dwarves with masses near the lower limit required for hydrogen fusion (about 75 Jupiters); the system has an aggregate mass of about 34% of the Sun's. At least one component is a flare star, and maybe all three; the system's variable star designation is EZ Aquarii.

EZ Aquarii A is a cool, dim, red dwarf of spectral type M5.0-5.5 Ve. It has only about a tenth the Sun's mass, about 8% to 35% of its diameter, and only 1/12,000th of its luminosity. Star A is also spectroscopic binary with an orbit period of only 3.8 days. Its companion is designated component C. EZ Aquarii C is a class M red dwarf with a mass less than a tenth the Sun's, close to the hydrogen fusion limit. EZ Aquarii B is a class M5.0 J Ve red dwarf with a luminosity only 1/30,0000 the Sun's, and also less than a tenth of its mass. Components AC and B have an average separation of about 1.22 AU, and an eccentric orbit (e=0.437) with a period of about 2.25 years.

A recent search for faint companions using the Hubble Space Telescope found no evidence of any large Jupiter- or brown dwarf-sized objects nearby.