asteroid

American  

[as-tuh-roid] / ˈæs təˌrɔɪd /

noun

• asteroids
  plural

1. 

   Astronomy. any of millions of small celestial objects revolving around the sun, often irregularly shaped and having a great range in size, from as small as 6 feet (2 meters) across to about 620 miles (998 kilometers) across: the vast majority of known asteroids exist within the asteroid belt.

2. Zoology. a starfish; an asteroidean.

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adjective

1. starlike.

asteroid British  

/ ˈæstəˌrɔɪd /

noun

1. Also called: minor planet, planetoid. any of numerous small celestial bodies that move around the sun mainly between the orbits of Mars and Jupiter. Their diameters range from 930 kilometres (Ceres) to less than one kilometre

2. Also called: asteroidean. any echinoderm of the class Asteroidea; a starfish

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adjective

1. of, relating to, or belonging to the class Asteroidea

2. shaped like a star

asteroid Scientific  

/ ăs′tə-roid′ /

1. Any of numerous small solar system bodies that orbit the Sun primarily in the asteroid belt, a region between the orbits of Mars and Jupiter. Asteroids are intermediate in size between planets and meteoroids with diameters that measure between approximately one hundred and several hundred kilometers. While more than 1,800 asteroids have been cataloged, and as many as a million or more smaller ones may exist, their total mass has been estimated to be less than three percent of the Moon's. Asteroids are thought to be left over from the early formation of the solar system, when planetesimals in a protoplanetary disk were scattered after coming under Jupiter's gravitational influence. The continuing collision of planetesimals that remained between Jupiter and Mars caused many of them to fragment, creating the asteroids that exist today.

2. Also called minor planet planetoid

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asteroid Cultural  

1. A small planet that revolves around the sun. The largest asteroid is only about six hundred miles in diameter. (See asteroid belt.)

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Other Word Forms

Derived Forms

• asteroidal
  adjective
• interasteroidal
  adjective

Inflected Forms

Nouns

• asteroids
  plural

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Etymology

Origin of asteroid

First recorded in 1795–1805; from Greek asteroeidḗs “starry, starlike”; see star, -oid

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Explanation

An asteroid is a large, irregularly shaped object in space that orbits our Sun. If one of these giant rocks ends up on a collision course with Earth, we are in for big trouble. An asteroid is like a comet. However, while comets are mostly made of ice, asteroids are made up of rock or even metal. This makes them dangerous because they can cause a lot of damage if they collide with a planet. The craters on the Moon were formed by asteroids and some think it was an asteroid that wiped out the dinosaurs. Around a million asteroids are located between Mars and Jupiter in an area called the “asteroid belt.”

Example Sentences

See Examples For:

asteroid asteroids

That experiment provided the first demonstration that X-rays could deflect a small piece of asteroid material.

From Science Daily ● Nov. 8, 2026

To investigate how different asteroid shapes respond to nuclear blasts, Moore and his colleagues developed what they describe as the most accurate asteroid deflection model yet.

From Science Daily ● Nov. 8, 2026

The new computer model allows researchers to reconstruct an asteroid using detailed 3D images captured during spacecraft flybys.

From Science Daily ● Nov. 8, 2026

The new simulation tools could eventually help mission planners identify the most effective way to deflect a threatening asteroid.

From Science Daily ● Nov. 8, 2026

Sixty-six million years ago, give or take a few centuries, an asteroid about the size of Manhattan Island slammed into Earth near what we now call the Yucatán Peninsula of Mexico.

From "Fallout: Spies, Superbombs, and the Ultimate Cold War Showdown" by Steve Sheinkin

By better understanding how nuclear X-rays interact with the complex surfaces of real asteroids, scientists are moving closer to predicting which strategies would work best.

From Science Daily ● Nov. 8, 2026

For the first time, its onboard camera has captured the two asteroids Didymos and Dimorphos as separate objects rather than a single point of light.

From Science Daily ● Nov. 3, 2026

The brand-new Vera C. Rubin Observatory is supposed to complete a groundbreaking “survey” of the universe, the most comprehensive catalog of its galaxies, asteroids, supernovas and black holes ever completed.

From The Wall Street Journal ● Nov. 2, 2026

"They're both actually quite large as far as these asteroids that are named after people tend to be, because most of the really large ones were discovered first," Nežič said.

From BBC ● Nov. 1, 2026

The rest of our family and friends are asteroids and comets floating around the planets orbiting the Sun.

From "Wonder" by R. J. Palacio

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Related Words

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