4 Centauri
4 Centauri is a multiple star in the constellation Centaurus, approximately 640 light years from Earth. It has a combined apparent magnitude of +4.71. The primary is a blue-white B-type subgiant with a spectroscopic companion, while the secondary is an Am star also with a spectroscopic companion.
4 Centauri is a hierarchical quadruple star system. The primary component of the system, 4 Centauri A, is a spectroscopic binary, meaning that its components cannot be resolved but periodic Doppler shifts in its spectrum show that it must be orbiting. 4 Centauri A has an orbital period of 6.927 days and an eccentricity of 0.23. Because light from only one of the stars can be detected, some parameters such as its inclination are unknown. The secondary component, is also a single-lined spectroscopic binary. It has an orbital period of 4.839 days and an eccentricity of 0.05. The secondary component is a metallic-lined A-type star. The two pairs themselves are separated by 14 arcseconds; one orbit would take at least 55,000 years.