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Bet You Didn't Know These Cool Facts About Asteroids

Rocks! In outer space! They're a lot more interesting than you might think!

Maria Bailey · 22 days ago

asteroid facts

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There are millions of asteroids orbiting around the Sun, but many of us know so little about these mysterious rocky worlds. In honor of International Asteroid Day on June 30th (yes, that’s a thing), we’ve decided to unearth (yes, pun intended) out-of-this-world facts (okay, we get it) about asteroids in our solar system. 

First things first, what is an asteroid?

In short, an asteroid is an inactive, small rocky object — relatively speaking — that orbits the Sun, just like planets. However, they’re too small to be considered planets and are instead referred to as planetoids or minor planets. 

Just how “small” are asteroids?

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Size is relative — and in the context of space, asteroids, which could span hundreds of miles or several feet across, are considered small. The largest asteroid in our solar system, called Vesta, is about 329 miles (530 kilometers) in diameter. Other asteroid bodies, however, can be less than 33 feet (10 meters). To put the “small” size of asteroids into perspective, the total mass of all asteroids in our solar system is less than that of Earth’s moon.

How many asteroids are there?

There are at least 1 million-plus asteroids in our solar system! According to the latest count by NASA, there are 1,097,106 asteroids in total

What are the different types of asteroids?

There are millions of asteroids in our solar system, and most of them live in the main asteroid belt, a region between the orbits of Mars and Jupiter. Asteroids that go in front of and behind Jupiter are called Trojans. Asteroids that come close to Earth are referred to as Near-Earth Objects (go figure), or NEOs for short. The latter are the asteroids our friends at NASA keep a close eye on. 

How are asteroids formed?

Asteroids are leftover remnants from the early formation of our solar system about 4.6 billion years ago! The formation of Jupiter prevented any planetary bodies from forming between Mars and Jupiter, creating a gap between the two planets (now known as the asteroid belt) where small objects would collide with each other and fragment into what we call asteroids.  

How fast do asteroids travel?

Asteroids zip through space at astonishing velocities. The speed at which asteroids move depends on their distance to the Sun. The closer they are, the greater the speed. That said, even Earth-crossing asteroids, or NEOs, travel around 25 kilometers per second — yep, per second! To put this crazy speed into perspective, it takes Apollo astronauts approximately three days to travel from Earth to the Moon. Can you guess how long it would take a typical asteroid to travel the same journey? If you guessed approximately 4 hours, you are correct!

Okay, but what is the difference between an asteroid, comet, meteoroid, meteor, and meteorite?

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These terms are often (incorrectly) used interchangeably. However, they are not the same thing! As we already know, an asteroid is an inactive body of rock that orbits the Sun. On the other hand, a comet is an active object covered in ice that vaporizes in sunlight to create a tail of dust and gas. This brings us to a meteoroid — a small particle from a comet OR an asteroid orbiting the Sun. Okay, but how about a meteor? You might know these best as shooting stars! A meteor refers to a light phenomenon that develops when a meteoroid enters the Earth’s atmosphere and vaporizes. Last but not least, a meteorite survives the journey to the Earth’s atmosphere and lands on the Earth’s surface. Pretty cool, right?

But wait, asteroids have moons?

While moons are something we would typically associate with orbiting a planet, moons (or rather, mini-moons) orbit asteroids, too! In fact more than 150 asteroids are known to have moons. A more recent example was found orbiting Asteroid 2004 BL86 — check it out below!

Radar images of 2004 BL86 and its moon

By NASA/JPL-Caltech, Public Domain via WikiMedia Commons

Did an asteroid kill the dinosaurs?

dinosaur

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Maybe? Evidence suggests dinosaurs and other creatures rapidly disappearing around 65 million years ago. According to National Geographic, there are two hypotheses for this event: either an asteroid or comet collided with Earth, or there was a huge volcanic eruption. A case for the asteroid hypothesis stems from the discovery of iridium — a rare element here on Earth but not in meteorites — has been discovered across the world. That said, iridium can also be found inside the Earth’s center, making a case for the theory that a massive volcanic eruption could have wiped out dinosaurs instead. In any case, the debris from either scenario is said to have blocked the Sun, resulting in mass die-offs of plants, animals, and other food sources, so that the remaining survivors of the impact eventually starved.

Do asteroids have names?

You bet your Aalamiharandi they do. The Harvard Smithsonian Center for Astrophysics keeps a list of current asteroid names, from ASCII to Zyskin, including some asteroids named for sci-fi characters like Spock from Star Trek, as well as asteroids named for people and celebrities like author Octavia Butler, painter Norman Rockwell, and rock musician Frank Zappa. Most asteroids, however, are given a number and are named for an astronomer or location connected with how they were identified.