The farthest constellation visible to the naked eye is the Andromeda Galaxy, located within the constellation of the same name, Andromeda. The Andromeda Galaxy (M31) is a spiral galaxy situated approximately 2.537 million light-years from Earth, making it the nearest spiral galaxy to our own Milky Way. While individual stars within constellations do not measure distance in the same way that galaxy structures do, Andromeda as a whole is discernible from Earth as a faint, smudgy patch in regions with minimal light pollution.
For naked-eye observation, the specific conditions play a crucial role. In optimal viewing situations, such as clear, dark skies well away from city lights, the galaxy can be detected with the naked eye, particularly when Andromeda is high in the sky. Observers can typically find it by locating the “Great Square of Pegasus” and then following the line to Andromeda.
Although Andromeda itself is not a constellation but a galaxy, it resides within the Andromeda constellation, and its visibility significantly surpasses any individual star distance. It’s important to note that visibility varies based on location, atmospheric conditions, and observer experience, but the Andromeda Galaxy holds the distinction of being the most distant object observable without telescopic aid.