Astronomy
How the Solar Wind Shapes Comet Tails
Quick fact
A comet's ion tail can be millions of kilometers long, yet it is so thin that the gas in it is less dense than some laboratory vacuums on Earth.
Why this is interesting
Comets have two tails, but they always point away from the Sun—even when the comet is moving back out. Why? It’s not just about motion; it’s about a constant invisible breeze from our star.