 There's this idea called the Copernican principle, and it states basically that our solar system shouldn't be the only one. There should be many solar systems in our galaxy, and they should all have the same basic building blocks. Back in 1992, the first planet orbiting another star was discovered. We call those exoplanets, and since then we've discovered 3,700 more. But there should be more than just planets orbiting these stars. After all, our solar system has moons, asteroids, and comets. Astronomers have announced the first evidence of comets orbiting another star, or exocomets. Now to understand how you find an exocomet, we first need to understand how you find an exoplanet. If an exoplanet passes in front of its star from our point of view, it will block some of the light. Only a small amount of light will be blocked, but we can detect it and infer that a planet is orbiting that star. Now a planet is a roughly spherical object, and so will create a symmetric dip in light. But a comet is a different story. As we know from our solar system, if a comet gets too close to the sun, the ice on the surface of the comet will sublimate and create a big ball of gas, thousands of kilometers in size. We call that a coma. The solar wind pushes on the coma, which creates a cometary tail. Now if we go back to how we discover exoplanets, what should we expect to see when an object with a tail passes in front of its star? It should create an asymmetric dip in light. And that's exactly what astronomers found buried in the data of the Kepler space telescope. An asymmetric dip in light, which means a non-spherical object passed in front of the star. That's the tell-tale sign of a comet from another planetary system. While this is an incredible result, it is in a way expected. Our solar system shouldn't be the only one, and so as we keep investigating other stars and the objects that are orbiting them, it's exciting to think what else we might find.