Backyard Observatory

Here’s the Difference Between Asteroids, Meteors, and Meteorites

The Huey, Dewey, and Louie of space rocks.

There are a lot of familiar space terms whose definition can feel hazy when you're a decade-plus removed from high school. You understand the gist of it, but the details get a bit fuzzy around the edges. Asteroids? Something to do with belts, right? Meteors? Those are the ones that wrote "The Handclapping Song"?

Here's a quick primer on the difference between these space rocks, so you sound like an expert next time you're watching a meteor shower in your backyard.

What is an asteroid?

An asteroid is an object composed of rock and metal that orbits the sun but is much smaller than a planet. The majority of asteroids in our solar system reside in the asteroid belt between Mars and Jupiter. They are left over from the formation of the solar system and our sun 4.6 billion years ago. The majority of the material inside the cloud of gas and dust that was here before our solar system became the sun. Some of the leftover detritus became planets. The extra bits become asteroids, which never formed into a planet.

Asteroids can be a pebble or large enough to be considered a dwarf planet. One famous example of the latter is Ceres. At almost 600 miles across, it's the largest asteroid in the asteroid belt. But even so, it's many times smaller than our moon. Ceres is one-third of the total mass in the asteroid belt, reports Space.com, yet it only equals only about 4% of the moon's mass.

What is a meteor or meteorite?

There are a few stages of this. NASA notes that when two asteroids collide and a little chunk breaks off, that's a meteoroid. If a meteoroid heads toward Earth and enters the atmosphere, it becomes a meteor. That meteor will likely vaporize as it falls to Earth. From the ground, you can see the glowing rock, which is often referred to as a shooting star even though it's not a star. 

If the meteor doesn't completely burn up and it lands on the ground, that rock is called a meteorite. When we talk about meteor showers, it's because those rocks are burning up in the sky. If it was a meteorite shower, it could be a painful experience.

What is a comet?

Comets are also formed of material left from the formation of the solar system. However, unlike an asteroid, comets aren't just rocky material. They're additionally composed of ice and gas.

Comets also orbit the sun, though not like an asteroid. In his description of meteor showers, Gregory A. Lyzenga, a physics professor at Harvey Mudd College, writes that the orbit of a comet is more of an "elongated ellipses." As a comet moves toward the sun, the ice and dust inside the comet vaporize to form the tail. Interestingly, the tail always points away from the sun. So, the tail isn't necessarily behind the comet. It can also be beside or in front of the comet's path.

Comets leave a trail of dust and debris in their wake. Meteor showers can happen when the Earth's orbit intersects the orbital path of a comet. The dust left by the comet falls into the Earth's atmosphere and becomes the bright meteors you've maybe looked up at on a summer night. 

Ready to go stargazing?

Here are all the best stargazing events that you can get out and see this month or you could stay in a stream the northern lights from home. If you're just getting started, check out our guide to astronomy for beginners

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Dustin Nelson is a Senior Staff Writer on the news team at Thrillist. Follow him @dlukenelson.