Asteroids are small Solar System bodies that orbit the Sun. Made of rock and metal, they can also contain organic compounds (some scientists suggest that asteroids could have brought they necessary chemicals to start life on Earth). There are millions of them, and they are often grouped by their composition.There are currently over 600,000 known asteroids in our solar system. Asteroids are also referred to as minor planets or planetoids. Asteroids vary greatly in size, some feature diameters as small as ten metres while others stretch out over hundreds of kilometres. But objects under ten metres in diameter are generally regarded as meteoroids. The majority of the known asteroids in the Solar System orbit the Sun in a band between the orbits of Mars and Jupiter. This band is commonly referred to as the Asteroid Belt.
Although there are hundreds of thousands of asteroids in the Asteroid Belt, there are only around 200 known that exceed 100 km in diameter, making the majority of the asteroids realtively small objects. Current theories suggests that the asteroids found in the Asoteroid Belt are the remnants of a planet that failed to form during the development of the Solar System.
Some asteroids have moons of their own! Some asteroids are blown out comets. When the ice is gone, all that remains is the rocky material. While asteroid impacts were more common in the past, they aren’t as frequent today.
An asteroid impact some 65 million years ago contributed to the extinction of the dinosaurs. (It was one of several factors that affected all life on Earth at that time.) In 1801, Italian astronomer Giuseppe Piazzi discovered what he believed to be a new planet. He named the newfound object Ceres, after the Roman goddess of the harvest. Soon after Ceres’ discovery similar objects were found. It was soon realized that these new objects were not, in fact, planets, but some other type of celestial body.
As well as being the first asteroid discovered, Ceres is also the largest known asteroid at 933 kilometers (580 miles) across. Ceres was given dwarf planet status in 2006, along with Pluto, Eris, Makemake and Haumea. One characteristic these objects shared was their resemblance to distant stars as viewed through the telescopes of the time (1800s). As a result of their similar appearance to stars the objects were named asteroids, meaning “star shaped.”
The technology used for discovering asteroids has improved dramatically since original discoveries and astronomers now have access to a range of powerful telescopes to aid in their research and discoveries. Asteroids are rich in precious metals and other metals, as well as water. A car-sized meteoroid (a piece of asteroid) falls into Earth’s atmosphere about once a year. The result is a beautiful fireball, but the meteoroid usually burns up before reaching the ground.
An asteroid about 0.15 kilometers (0.1 miles) in width is believed to have exploded over Siberia, causing damage within a radius of hundreds of kilometers (miles).Most asteroids are irregular in shape because they are too small to exert enough gravitational pull to become spherical in shape.