* Comets have elliptical orbits: They don't travel in a perfect circle around the Sun. They come close, then swing out very far.
* They come in different types: Some comets, like Halley's Comet, have relatively short orbital periods and stay within our solar system. Others, called "long-period comets", can come from the Oort Cloud, a vast region trillions of miles from the Sun, taking thousands of years to complete an orbit.
So, instead of a specific distance, here's how to think about it:
* Perihelion: The closest point a comet gets to the Sun is called perihelion. This can be anywhere from within the orbit of Mercury to beyond the orbit of Mars.
* Aphelion: The furthest point a comet gets from the Sun is called aphelion. This is where the variation is huge. Some comets reach the outer edges of our solar system, while others venture far beyond the orbits of Pluto and even into the Oort Cloud.
In short: Comets can be as close to the Sun as a few million miles (perihelion) or billions of miles (aphelion), depending on their specific orbit.
