The night sky is a shared wilderness. On a dark night, away from the city lights, you can see the stars in the same way as your ancestors did centuries ago. You can see the Milky Way and the constellations associated with stories of mythical hunters, sisters and journeys.

But like any wilderness, the night sky can be polluted. Since Sputnik 1 in 1957, thousands of satellites and pieces of space junk have been launched into orbit.

For now, satellites crossing the night sky are largely a curiosity. But with the advent of satellite constellations—containing hundreds or thousands of satellites—this could change.

The recent launch of BlueWalker 3, a prototype for a satellite constellation, raises the prospect of bright satellites contaminating our night skies. At 64 square meters, it's the largest commercial communications satellite in low Earth orbit—and very bright.

Pollution of the night sky