Asteroids,
Meteoroids, and CometsAsteroids,
Meteoroids, and Comets
Besides stars, asteroids can also be found in galaxies. Asteroids are
basically small planets that move in orbit around the sun.
Within the Milky Way, there is a huge collection of asteroids called an
asteroid belt. This belt is found in the space between two of our planets, Mars
and Jupiter. This belt contains thousands of these asteroids.
The largest known
asteroid is Ceres which is about 640 miles in diameter.
Pa1as and Vesta are the second largest and measure roughly 340 miles
across. There are currently about 200 known asteroids circling the sun that are
over 60 miles across and thousands of smaller ones.
Meteors are found in our solar system, too. Meteors are small, solid bodies that enter a planet’s atmosphere.
Every year hundreds of meteors fall to earth. Most however, reach the
surface of our planet as dust as they are destroyed by friction with our
atmosphere as they pass through it. It is this friction that causes a meteor to
glow as it literally catches fire from the high temperatures created. If a
meteor reaches earth intact, it is called a meteorite. There have been several
craters in the world have been created by meteorites.
One of them, Meteor Crater, is in Arizona. It has been theorized that a
large meteorite caused the extinction of the dinosaurs as its impact could have
disturbs the earth’s atmosphere by creating a large cloud of dust that blocked
the sun’s -rays for years.
Comets are small bodies that are characterized by a long, glowing tail.
Comets revolve around the sun. Often called “dirty snowballs”, comets consist of dust and ice and
are only visible when they pass in front of the sun and the light reflects off
the ice particles.
Comets are classified into three types, based on the length of the time
it takes them to orbit around the sun once.
A short period comet is one that
orbits the sun in 3-9 years. A long period comet,
such as Halley’s comet, takes 75-100 years to complete an orbit. A very long period comet takes
thousands of years to move completely around the sun.
Lastly, satellites are objects that revolve around a planet or a star. An example of a satellite is our moon. It orbits the earth in a similar way that earth orbits the sun. With the exceptions of Mercury and Venus, all the planets have at least one known satellite. Saturn has the most at last count with over 20 documented satellites orbiting the giant planet.
