The Science Behind the Meteor That Lit Up the North American Sky

What's the difference between a meteor, a meteoroid, and a meteorite?

On January 16, parts of the sky looked like they were on fire. But what people from New York City to sections of Canada saw was actually a meteor, rather than a foreshadowing of the end of the world.

According to NASA, the space chunk entered the atmosphere about 5 miles west of New Haven, Michigan, and then traveled northwest at a relatively slow 28,000 miles per hour. Estimates say the rock likely measured three to six feet across, and could have weighed more than a ton. (Read our January sky guide.)

But what is a meteor? A meteorite? Those and other questions explained below.

So ... what is a meteor?

Let's start with meteoroids. Meteoroids, along with asteroids and comets, are chunks of interplanetary matter in outer space. When meteoroids penetrate Earth's atmosphere, they're called meteors, also known as "shooting stars" or "falling stars."

Meteor showers and meteor storms happen when many meteors are visible at once, and meteorites are the rock remnants that remain after a meteor has burned up and come into contact with the planet's surface.

How fast do these things fall?

Meteors normally collide into the thermosphere layer of Earth's atmosphere, which is about 50 to 75 miles up. If a meteor is moving particularly fast—say, around a whopping 160,000 miles per hour—it can be visible above this band; if a meteor is relatively slow-moving—at around 25,000 miles per hour—it can sometimes be seen at a lower altitude. The space chunks have to be slow when they enter the atmosphere at evening hours but fast during the morning. (Read: "Surprise Meteor Lights Up Harvest Moon Festival")

When a hurtling meteor comes into contact with the air molecules in the atmosphere, it creates friction and heats up. It'll then often explode into a bolide in the atmosphere, causing a fireball as it falls toward Earth. Shortly after a large meteor streaks across the sky, a shock wave follows.

That sounds dangerous.

It's not, typically. Meteorites, leftover bits of meteors, are normally so small they vaporize before reaching Earth's surface. They can be stony and metallic solid rocks, or "dustballs" made of low-density material that has made many trips near the Sun. If they're sturdy enough to withstand the atmospheric drop, meteorites can range from pebble-size to boulder-size. (Check out this map to see where every meteorite on Earth has fallen.)

Wait, did you say "boulder-size"?

Yes, but don't worry—meteorites rarely injure people. Early Earth saw more meteorite impacts than the planet we live on today. But thousands of tiny meteorites still hit the ground each year, landing in remote forests or the open ocean. The fragments are most commonly found in desert regions, where low precipitation prevents them from eroding and minimal vegetation cover makes them easier to find.

However, the first record of a person being hit by a piece of space matter in the United States was Ann Hodges, who was severely bruised on her hip by an 8-pound hard meteorite that crashed through her roof in Sylacauga, Alabama, in November 1954.

Generally, meteorites are being caught on camera much more frequently these days, as many more people have cameras and cellphones available. Recordings of a large meteor over Russia in 2013 caused a viral sensation online.

<p>Comet C/2001 Q4, also known as NEAT, emits a blue-and-purple glow as it moves through the cosmos in May 2004. Its coma, or head, and a portion of its tail are visible in this shot, as are myriad stars. This image was taken by telescope from Kitt Peak National Observatory near Tucson, Arizona.</p>

Comet C/2001 Q4, also known as NEAT, emits a blue-and-purple glow as it moves through the cosmos in May 2004. Its coma, or head, and a portion of its tail are visible in this shot, as are myriad stars. This image was taken by telescope from Kitt Peak National Observatory near Tucson, Arizona.

Photograph courtesy T. Rector (University of Alaska Anchorage), Z. Levay and L. Frattare (Space Telescope Science Institute), and National Optical Astronomy Observatory/Association of Universities for Research in Astronomy/National Science Foundation

A previous version of this story misidentified the city where the meteor entered the atmosphere. The story has been updated.

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