HD 91312
HD 91312 is a multiple star system in the northern circumpolar constellation Ursa Major. Faintly visible to the naked eye, it is the brightest star of Ursa Major without Flamsteed designation with a combined apparent visual magnitude of 4.72. The system is located at a distance of 109 light-years from the Sun based on parallax. The radial velocity is poorly constrained, but it appears to be drifting further away at a rate of ~9 km/s.
This was identified as a visual binary by John Herschel in 1831. The pair have an angular separation of, equivalent to a linear projected separation of. Variations in the radial velocity as well as direct imaging, indicate the presence of a low-mass stellar companion. This companion is an early-to-mid red dwarf, and orbits the primary on an edge-on orbit with a semi-major axis of 9.7 au. This is a young system with an age of around 200 million years. It display an infrared excess from a circumstellar disk of dusty debris. It has a mean temperature of and is orbiting from the inner pair.
This star is relatively bright, but it was rarely included in old catalogues. Catalogues and atlases it was not included in are, for example, those by Ptolemy and all its derivatives and translations, Tycho Brahe, de Houtman, Bayer, Kepler, Schiller, Halley, Flamsteed and Bradley. Catalogues and atlases it was included in are those by Hevelius and Bode . Bode used extended Bayer designations for some stars, and HD 91312 also was assigned designation "w", whereas original Bayer designations for Ursa Major stars are all Greek letters and Latin letters from "A" to "h".