Once you’ve made it through a few grade-school science classes, you know that shooting stars aren’t really stars (though you might still make wishes on them from time to time).
But there’s more than one kind of flashy cosmic debris. Do you know what you’re looking at when you look to the sky? Asteroids, comets, and meteors often get confused, but they’re a little bit different—and also a bit the same. Here’s how to tell these phenomenons apart.
What’s an Asteroid?
Your chances of seeing an asteroid are pretty slim (unless you like watching sci-fi, or have a good telescope). These rocky celestial bodies mostly hang out in the asteroid belt, found between Mars and Jupiter. And most asteroids are about the size of a U.S. state, which is relatively tiny by the standards of space.
Asteroids were formed when the solar system was: they’re basically the leftover building blocks of planets. There are nearly 800,000 known asteroids. While most of them are in the asteroid belt, some do pass near the Earth, and experts predict that one’s certain to hit us sometime in the future—they just don’t know when or where.
What’s a Comet?
Comets were formed when the solar system was formed, too. But unlike asteroids, comets formed so far away from the sun that they stayed frozen. While asteroids only contain metal and rock, comets also contain frozen gases that haven’t had the chance to thaw.
Comets have orbits that sometimes bring them close enough to the Earth to be seen. Most of these visible comets look kind of boring. But sometimes, as the sun heats up and ignites the frozen elements, they can become impressively bright in the sky. These super-bright comets are rare and exciting, but many other, duller comets pass by us regularly as they orbit the sun.
What’s a Meteor?
Those shooting stars you see sometimes are actually meteors. And meteors are actually asteroids—they only become meteors when they burn up on contact with the Earth’s atmosphere. That’s why you see them glowing and streaking across the sky.
When many meteors come near the Earth at the same time, we have meteor showers. These regular events are a prime time to see shooting stars, and luckily, they’re very predictable.
What Else Is There?
You might also hear of meteoroids and meteorites. Meteoroids are simply meteors that haven’t yet entered the atmosphere. They can be as small as specks of space dust, or as large as ordinary asteroids.
And when meteors make it through the atmosphere to land on Earth, they’re called meteorites. Only the larger meteors survive to become meteorites, but by the time they land on Earth, they’re usually pretty small. The atmosphere burns up most of the rock and metal, leaving only a fraction behind to land on the ground.
Space is full of space rocks, and all of this debris initially came from the formation of the solar system. Asteroids, comets, and meteors simply have different names depending on where they are in relation to us. And most of the time, they aren’t much to look at—but when one of them comes into contact with the sun’s heat or the Earth’s atmosphere, they can light up the night sky in an unusual and memorable way.