三角座星系
Under exceptionally good viewing conditions with no light pollution, the Triangulum Galaxy can be seen with the 20/20 vision naked eye; to those viewers, it will sometimes be the farthest permanent entity visible without magnification. Its light diffuses (spreads) across a little more than a pinprick of the unmagnified sky, the cause of which is its broadness – this astronomers term a diffuse, rather than compact, object.