Alcor

Yes, Alcor has an apparent magnitude of about 4.0, making it faintly visible to the naked eye under dark sky conditions, though it is considerably dimmer than its nearby companion Mizar at magnitude 2.2. In antiquity, the ability to distinguish Alcor from Mizar was widely used as a test of visual acuity by Arab, Greek, and Persian astronomers.

Recent measurements of proper motion and parallax suggest that Alcor and Mizar are likely gravitationally associated, forming a true multiple star system rather than an optical double. The two are separated by about 11.8 arcminutes on the sky, corresponding to an estimated physical separation of roughly a quarter to a full light-year.

The Mizar-Alcor system contains at least six stars: Mizar itself is a quadruple system consisting of two pairs of spectroscopic binaries (Mizar A and Mizar B), while Alcor has been confirmed to have a fainter companion star, making it a binary. This makes the system one of the nearest and most accessible multiple-star groupings for amateur observation.

Alcor is located in the constellation Ursa Major, forming part of the handle of the Big Dipper asterism, approximately 82 to 83 light-years from Earth. It sits very close to the star Mizar, and together they have served as one of the most famous naked-eye double stars in astronomical history.