Interesting Facts about Asteroids

Asteroids are celestial bodies consisting of rocks and metals. They are mainly concentrated in the region known as the asteroid belt which lies between the orbits of Mars and Jupiter. Asteroids can be as big as Ceres, which is close to 1000 kilometers in diameter, or can be just a few feet in diameter. Whatever the size, asteroids are neither big enough to be called planets nor are they as small as comets. They are classified as minor planets that include the Kuiper Belt Objects.

Discovery
On January 1, 1801, Giuseppe Piazzi discovered the first asteroid which he initially thought to be a comet. He named this asteroid Ceres, after the Sicilian Goddess of grain. Ceres is also the largest asteroid to have been discovered so far. Soon, other large asteroids like Pallas, Juno and Vista were discovered. By the end of the 19th century, several hundred asteroids were discovered.

Formation of Asteroids
It was once believed that asteroids were formed by the explosion of a planet orbiting between Mars and Jupiter. However, according to present day astronomers, asteroids are debris left behind by the Big Bang that could not come together to form a tenth planet because of the effect of Jupiter's gravitational pull.

Asteroid Hits
Asteroids have been hitting the Earth since millions of years. However, due to the friction with Earth's atmosphere most of the asteroids get burnt. The asteroids that enter the Earth' s atmosphere are called meteors while the ones that get burnt and appear as shooting stars are called meteorites. According to the Giant Impact Theory, the Moon was created when Theia, an asteroid of the size of Mars, collided with the Earth in the early days of the solar system. However, some consider Theia to be more of a planetoid than an asteroid. The largest crater caused by an asteroid hit is the Chicxulub Crater in Mexico that is 180 km in diameter. The asteroid that formed the crater had a diameter of 10 km. This collision is supposed to be responsible for the extinction of a large number of flora and fauna including the dinosaur. However, the evidence of the largest asteroid hit is in the Vredefort crater in South Africa that is 300 km in diameter.

Impacts of Asteroid Hits
The damage that an asteroid's impact can cause depends mainly upon its mass and velocity, as these are the two factors that determine the energy that is released when an asteroid hits the Earth. While some asteroids are capable of sending thermal waves that can incinerate most flora and fauna within a few hundred kilometers, some larger asteroids can create huge impacts causing magma to cover areas as big as continents. The worst effect of an asteroid hit is the blocking out of sunlight for months together due to formation of dust clouds and soot in the upper atmosphere. This would hamper the green plants' ability to prepare food through the process of photosynthesis and the food chain would be disrupted.

Near-Earth Asteroids
Near-Earth asteroids are those that have moved closer to the Earth's orbit as they have been knocked out of the asteroid belt due to collision with other asteroids or comets, or due to the gravitational forces of Jupiter. They are classified into the following three groups:

• The Amors: These are near-Earth asteroids that cross the orbit of Mars but do not go out of the Earth's orbit.
• The Apollos: The orbits of these near-Earth asteroids cross the Earth's orbit but have an orbital period of greater than one year.
• The Atens: These near-Earth asteroids have orbits that cross the Earth's orbit but have an orbital period of less than one year.

Asteroids are currently being monitored for their probability of colliding with the Earth. Such studies have predicted that asteroids may hit the Earth on February 1, 2019 and March 16, 2880. The probability of the 2880 collision is as high as 1 in 300. A number of projects in the field of astronomy, like Spacewatch, Near-Earth Asteroid Tracking and Catalina Sky Survey are being carried out to detect any threat of such catastrophes.