Gravitational microlensing

Imagine that you're sitting on a very heavy bouncy ball that is constantly pulling you towards its centre. This is what we call gravity, the force that keeps us and everything we know from floating away into space. Now, let's say you notice a tiny bug on the very edge of the bouncy ball. Because the bug is so tiny, it doesn't have much mass, and doesn't really contribute much to the bouncy ball's overall gravity. But, as you move around on the ball, the bug's position relative to you changes, and sometimes it seems to block your view of the other side of the bouncy ball.

This is kind of like what happens with gravitational microlensing. In space, there are massive objects like stars and planets that also have gravity, just like our bouncy ball. When a star passes directly in front of another star from our perspective, the gravity of the closer, passing star can actually bend and magnify the light from the more distant star behind it. This brief and rare phenomenon is what we call gravitational microlensing.

Scientists use this to study distant objects in space that would otherwise be too faint or hard to see, like planets orbiting other stars. By measuring the way the microlensing effect changes the brightness of the background star, they can figure out some properties of the foreground object. Pretty cool, huh?