The Andromeda Galaxy sits 2.5 million light-years away and is the most distant object most people can see without a telescope. The photons reaching your eye left Andromeda 2.5 million years ago, before modern humans existed.
From a dark site it looks like a faint, elongated smudge in the constellation Andromeda, brightest at its core. The full galaxy covers a patch of sky wider than six full Moons, but only the core is bright enough to see by eye. Under perfect dark skies a few observers can also pick out the Triangulum Galaxy, about 2.7 million light-years away, which is eight times fainter. A telescope or a long camera exposure reveals the spiral arms. Andromeda is similar in size to the Milky Way and is the nearest large galaxy to us.
2.5 million light-years
Distance to the Andromeda Galaxy