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Asteroid vs. Comet: What's the Difference?

Edited by Harlon Moss || By Janet White || Published on January 30, 2024
Asteroids are rocky bodies in space, mainly in the asteroid belt, while comets are icy objects that develop tails when near the sun.

Key Differences

Asteroids are remnants from the early solar system, primarily made of rock and metal. Comets, on the other hand, are composed of ice, dust, and organic compounds, forming in the colder outer solar system.
Asteroids often have shorter, more circular orbits within the asteroid belt between Mars and Jupiter. In contrast, comets have long, elliptical orbits, taking them far beyond the planets.
Asteroids are generally smaller and have a more uniform, rocky appearance, while comets develop a distinctive glowing tail of gas and dust when they approach the sun, a result of their icy composition sublimating.
Asteroids can pose a collision risk with Earth, leading to significant impact events. Comets are less likely to collide with Earth but are visible from Earth when they pass close to the sun, showing spectacular tails.
Both asteroids and comets are of great interest to scientists. Asteroids provide insights into the early solar system's composition, while comets can offer clues about the solar system's formation and the origin of water and organic molecules on Earth.

Comparison Chart


Rocky, metallic
Icy, contains dust and organic compounds


Shorter, more circular, mainly in asteroid belt
Long, elliptical, extends beyond planets

Physical Appearance

Smaller, uniform, rocky
Develops glowing tail near sun

Potential Earth Interaction

Collision risk
Visible tail when near sun, less collision risk

Scientific Significance

Insights into early solar system
Clues about solar system formation, origin of water

Asteroid and Comet Definitions


A small rocky body orbiting the sun, primarily found in the asteroid belt.
The asteroid belt contains numerous asteroids varying in size.


A space object known for its spectacular tail and glowing coma.
Observing a comet's tail can provide valuable information about solar wind.


A space rock that can sometimes enter Earth's atmosphere.
When an asteroid enters the Earth's atmosphere, it can become a meteor.


An icy small Solar System body that, when passing close to the Sun, warms and begins to release gases.
Halley's Comet is perhaps the most famous comet, visible from Earth every 76 years.


A minor planet of the inner solar system.
Ceres, once classified as an asteroid, is now considered a dwarf planet.


An ancient, frozen remnant of the early solar system's formation.
Comets are like time capsules, holding clues to the solar system's history.


A celestial object composed of rock and metal.
Scientists study asteroids to understand more about the early solar system.


A solar system body with a highly elliptical orbit.
Comets often have long periods due to their elliptical orbits.


A natural satellite in space, smaller than a planet.
Many asteroids are captured by planets and become their moons.


A celestial object consisting of a nucleus of ice and dust and, when near the sun, a “tail” of gas and dust particles.
The comet's tail always points away from the sun due to solar wind.


(Astronomy) Any of numerous small solar system bodies that revolve around the sun, with orbits lying chiefly between Mars and Jupiter and characteristic diameters roughly between one and several hundred kilometers. Also called minor planet, planetoid.


A celestial body, observed only in that part of its orbit that is relatively close to the sun, having a head consisting of a solid nucleus surrounded by a nebulous coma up to 2.4 million kilometers (1.5 million miles) in diameter and an elongated curved vapor tail arising from the coma when sufficiently close to the sun. Comets are thought to consist chiefly of ammonia, methane, carbon dioxide, and water.


(Zoology) See starfish.


(astronomy) A small Solar System body consisting mainly of volatile ice, dust and particles of rock whose very eccentric solar orbit periodically brings it close enough to the Sun that the ice vaporises to form an atmosphere, or coma, which may be blown by the solar wind to produce a visible tail.




A celestial phenomenon with the appearance of such a body.


(zoology) Any member of the taxonomic class Asteroidea; a starfish


Any of several species of hummingbird found in the Andes.


(astronomy) A naturally occurring solid object, which is smaller than a planet, larger than a meteoroid and not a comet, that orbits a star and often has an irregular shape.


A member of the solar system which usually moves in an elongated orbit, approaching very near to the sun in its perihelion, and receding to a very great distance from it at its aphelion. A comet commonly consists of three parts: the nucleus, the envelope, or coma, and the tail; but one or more of these parts is frequently wanting. See Illustration in Appendix.


(astronomy) In the Solar system, such a body that orbits within the orbit of Jupiter


(astronomy) a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit


A starlike body; esp. one of the numerous small planets whose orbits lie between those of Mars and Jupiter; - called also planetoids and minor planets.


Any of numerous small celestial bodies composed of rock and metal that move around the sun (mainly between the orbits of Mars and Jupiter)


Shaped like a star


Where are asteroids located?

Most asteroids are located in the asteroid belt between Mars and Jupiter.

Can asteroids hit Earth?

Yes, asteroids can collide with Earth, though significant impacts are rare.

How big are asteroids?

Asteroids vary in size from small rocks to hundreds of kilometers in diameter.

Are comets visible from Earth?

Yes, some comets are visible from Earth when they pass close to the sun.

How often do comets appear?

It varies; some comets have short periods, while others may take hundreds of years to return.

What are asteroids?

Asteroids are small, rocky objects that orbit the sun, mostly found in the asteroid belt.

Do comets have orbits?

Yes, comets have long, elliptical orbits that take them far beyond the planets.

What are comets made of?

Comets are made of ice, dust, and organic compounds.

How do comets get their tails?

Comet tails are formed when the comet's ice warms up near the sun and releases gas and dust.

Can asteroids have moons?

Yes, some larger asteroids have their own small moons.

What is the largest asteroid?

The largest known asteroid is Ceres, which is also classified as a dwarf planet.

Have missions been sent to asteroids?

Yes, several space missions have studied asteroids up close.

What is a comet's nucleus?

The nucleus is the solid core of a comet, made of ice and dust.

Are asteroids dangerous?

While most asteroids pose no threat, larger ones could be dangerous if they collide with Earth.

What causes a comet's tail to form?

A comet's tail forms due to the solar wind and radiation pushing dust and gas away from the comet's nucleus.

Can comets become meteors?

No, comets do not become meteors. However, debris from comets can enter Earth's atmosphere as meteoroids.

Are new comets still being discovered?

Yes, astronomers continue to discover new comets with telescopes and space missions.

What is the difference between an asteroid and a meteoroid?

A meteoroid is smaller than an asteroid and can become a meteor when it enters Earth's atmosphere.

Do comets change?

Yes, comets can change, especially when they pass near the sun, losing mass and sometimes breaking apart.

How are asteroids named?

Asteroids are named by their discoverers, subject to approval by the International Astronomical Union.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.

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