What fundamental element's absence allows astronauts to see the Milky Way better than Earth observers?

The atmosphere

The primary reason for the stark difference in visibility between the view from orbit and the view from Earth is the absence of the atmosphere. On Earth, the atmosphere actively scatters sunlight, which is what causes the sky to appear blue during the day. This same scattering effect extends into the night, creating a light glow even in remote locations away from cities. This scattering process inherently dims the faint light emanating from distant stars and the diffuse glow that constitutes the Milky Way. In contrast, astronauts orbiting Earth on the International Space Station (ISS) experience no atmospheric interference, allowing the light traveling from the stars and nebulae of the Milky Way to reach their eyes unimpeded, resulting in a significantly clearer and more intense perception of the galaxy.