asteroid
Sign in to saveAn asteroid is a minor planet—an object larger than a meteoroid (thus 1 meter or larger) that is neither a planet nor an identified comet—that orbits within the inner Solar System or is co-orbital with Jupiter (Trojan asteroids). Asteroids are rocky, metallic, or icy bodies with no atmosphere, and are broadly classified into C-type (carbonaceous), M-type (metallic), or S-type (silicaceous). The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across to Ceres, a dwarf planet almost 1000 km in diameter. A body is classified as a comet, not an
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An asteroid is a rocky, metallic, or icy object at least 1 meter in size that orbits the Sun in the inner Solar System, distinct from planets and comets. Asteroids vary widely in size and composition, ranging from small rubble piles to bodies nearly 1,000 kilometers across, and they matter because understanding their characteristics and movements helps us track potential impacts and learn about the early Solar System.
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Article
43 sectionsContents
- Terminology{{anchor|Terminology}}<!-- Linked from "Comet" -->
- History of observations
- Discovery of Ceres
- Further search
- 19th and 20th centuries
- Naming
- Symbols
- Formation
- Distribution within the Solar System
- Asteroid belt
- Trojans
- Near-Earth asteroids
- Martian moons
- Characteristics
- Size distribution
- Largest asteroids
- Rotation
- Color
- Surface features
- Composition
- Water
- Organic compounds
- Classification
- Orbital classification
- Spectral classification
- Problems
- Active asteroids
- Dark comets
- Observation and exploration
- Ground-based observations
- Space-based observations
- Space probe missions
- Dedicated missions
- Planned missions
- Asteroid mining
- Threats to Earth
- Asteroid deflection strategies
- Fiction
- See also
- Notes
- References
- Further reading
- External links
An asteroid is a minor planet—an object larger than a meteoroid (thus 1 meter or larger) that is neither a planet nor an identified comet—that orbits within the inner Solar System or is co-orbital with Jupiter (Trojan asteroids). Asteroids are rocky, metallic, or icy bodies with no atmosphere, and are broadly classified into C-type (carbonaceous), M-type (metallic), or S-type (silicaceous). The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across to Ceres, a dwarf planet almost 1000 km in diameter. A body is classified as a comet, not an asteroid, if it shows a coma (tail) when warmed by solar radiation, although recent observations suggest a continuum between these types of bodies.
Of the roughly one million known asteroids, the greatest number are located between the orbits of Mars and Jupiter, approximately 2 to 4 astronomical units (AU) from the Sun, in a region known as the main asteroid belt. The total mass of all the asteroids combined is only 3% that of Earth's Moon. The majority of main belt asteroids follow slightly elliptical, stable orbits, revolving in the same direction as the Earth and taking from three to six years to complete a full circuit of the Sun.