Alula Australis

Alula Australis (ξ Ursae Majoris) was the first binary star system to have its orbital period mathematically calculated, accomplished by French astronomer Félix Savary in 1828. This calculation demonstrated that binary stars follow Keplerian orbital mechanics, confirming that Newton's laws of gravitation apply beyond our solar system.

Yes, Alula Australis is visible to the naked eye under reasonably dark skies with an apparent magnitude of approximately 3.79, though resolving its binary components requires a telescope. Its name derives from Arabic, meaning "first leap," referring to its position near the foot of the Great Bear constellation.

Alula Australis is a complex multiple star system with at least five identified components. The primary visible pair consists of two stars that are themselves each spectroscopic binaries, and a fainter companion designated ξ Ursae Majoris C orbits at a wider separation, making this one of the more architecturally complex nearby stellar systems.

Savary calculated the orbital period of the Alula Australis binary pair to be approximately 60 years, which is remarkably close to modern refined measurements of about 59.8 years. His calculation was based on positional observations originally made by William Herschel, who first resolved the pair as a binary star in 1780.