Asteroids Explained Briefly
Asteroids are small rocky and metallic objects that are in orbit around the sun. They are smaller than planets and larger than meteoroids. Asteroids are also known as minor planets or planetoids. Most of the asteroids are in the asteroid belt between the orbits of Mars and Jupiter. However, some have orbits are found inside the Earth’s orbit to beyond Saturn’s orbit. Some have even crossed the Earth’s path and even hit the Earth in the past.
Asteroids range in size from the dwarf planet Ceres, which has a diameter of about 950 kilometers to rocks that measure roughly ten meters across. The three largest known asteroids is the Ceres, and the 2 Pallas and 4 Vesta both with diameters of over 500 kilometers. These three most resemble miniature planets as they are roughly spherical and have partially differentiated interiors. The three “miniature planets” are also considered as protoplanets, planetary embryos roughly the size of the moon which collided with each other and formed into the planets that exist today. The smaller and irregularly shaped asteroids which are more common are thought to be surviving planetesimals or fragments of larger bodies which the small building blocks of the planets that existed when the Solar System was just forming.
The largest asteroid belt in our solar system is the main asteroid belt which exists between the orbits of Mars and Jupiter. The belt contains more than 200 asteroids larger than 100 kilometers, more than 750,000 asteroids larger than 1 kilometer, and millions of smaller asteroids. Many asteroids are placed in groups and families according to their orbital characteristics.
Asteroid families are believed to be fragments of a past asteroid collision while asteroid groups contain asteroids that are unrelated to each other but share broadly similar orbits. It is also recently found out that the shape of an asteroid can help in determining the age of the asteroid. Older asteroids tend to have rounder shapes while younger ones tend to have a usually elongated variety of shapes. These asteroids become rounder as they age due to their being impacted throughout their lifetime. This manner is similar to erosion.
There are several theories in the origin of the asteroids. The leading theory indicates that asteroids are objects that are left over from the time the planets formed and most known asteroids are the shattered remains of larger objects. Another theory states that asteroids are the remains of a planet that was destroyed by a collision. Most astronomers now believe that asteroids are the remnants of a planet that failed to form. This theory especially explains the existence the main asteroid belt in our solar system. It is near impossible for a planet to form in the main asteroid belt due to the gravitational interference of Jupiter.
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