one of the closest bright stars visible to the naked eye. It has a magnitude of 0.77 and is approximately 16.5 light-years away from us. It is only 11 times brighter and has a diameter one and a half times larger than our Sun. Altair is also an optical double star, with a companion of magnitude 10 located at a distance of 165 arcseconds, still visible with an 8 cm telescope.