minor members of the solar system
MINOR MEMBERS OF THE SOLAR SYSTEM
ASTEROIDS
Asteroids are small rocky bodies that have been likened to “flying mountains.” The largest, Ceres, is about 1000 kilometers in diameter, but most are only about 1 kilometer across. The smallest asteroids are assumed to be no larger than grains of sand.
Most asteroids lie between the orbits of Mars and Jupiter. They have orbital periods of three to six years. Some asteroids have very eccentric orbits and travel very close to the sun, and a few larger ones regularly pass close to Earth and the moon.
Many of the most recent impact craters on the moon and Earth were probably caused by collisions with asteroids.
Many asteroids have irregular shapes. Because of this, planetary geologists first speculated that they might be fragments of a broken planet that once orbited between Mars and Jupiter. Others have hypothesized that several larger bodies once coexisted in close proximity, and their collisions produced numerous smaller ones. The existence of several families of asteroids has been used to support this explanation.
COMETS
Comets are the shining wanderers of the solar system. With their glowing tails that may stretch 100 million kilometers through space.
Most comets reside in the outer fringes of the solar system, far beyond Pluto. For all their apparent size in the sky, comets are actually fairly small objects. When a comet begins its trip down past the Sun, it is probably a chunk of "dirty ice," a mixture of rock dust and ice a few kilometers across, much smaller than the typical observed asteroid.
As it speeds towards the Sun, the heat from the Sun evaporates the ice, and the gases thus released blow dust particles outward from the solid body or nucleus. Radiation from the Sun ionizes the released atoms, producing a tail that glows in the sky like a neon sign; the dust particles reflect sunlight and form another, smoother tail. But not all develop a tail that extends for millions of kilometers.
ASTEROIDS
Asteroids are small rocky bodies that have been likened to “flying mountains.” The largest, Ceres, is about 1000 kilometers in diameter, but most are only about 1 kilometer across. The smallest asteroids are assumed to be no larger than grains of sand.
Most asteroids lie between the orbits of Mars and Jupiter. They have orbital periods of three to six years. Some asteroids have very eccentric orbits and travel very close to the sun, and a few larger ones regularly pass close to Earth and the moon.
Many of the most recent impact craters on the moon and Earth were probably caused by collisions with asteroids.
Many asteroids have irregular shapes. Because of this, planetary geologists first speculated that they might be fragments of a broken planet that once orbited between Mars and Jupiter. Others have hypothesized that several larger bodies once coexisted in close proximity, and their collisions produced numerous smaller ones. The existence of several families of asteroids has been used to support this explanation.
COMETS
Comets are the shining wanderers of the solar system. With their glowing tails that may stretch 100 million kilometers through space.
Most comets reside in the outer fringes of the solar system, far beyond Pluto. For all their apparent size in the sky, comets are actually fairly small objects. When a comet begins its trip down past the Sun, it is probably a chunk of "dirty ice," a mixture of rock dust and ice a few kilometers across, much smaller than the typical observed asteroid.
As it speeds towards the Sun, the heat from the Sun evaporates the ice, and the gases thus released blow dust particles outward from the solid body or nucleus. Radiation from the Sun ionizes the released atoms, producing a tail that glows in the sky like a neon sign; the dust particles reflect sunlight and form another, smoother tail. But not all develop a tail that extends for millions of kilometers.