asteroid is a cosmic body that circles in outer space around the Sun, mainly between the orbits of Mars and Jupiter. Asteroids have a few hundred kilometers and irregular shapes, which catch fire when they come into contact with the Earth's atmosphere.
Asteroids are usually made up of rock, metal and carbon and are larger than a meteor and smaller than a planet.
Etymologically, the word asteroid arose from the addition of the Greek words "aster", which means "star" and the suffix "eidos", which means "similarity", that is, asteroid means "starlike" or "little planet".
In the late eighteenth and early nineteenth centuries, scientists and astronomers thought that an indistinct body that wandered between the orbits of Mars and Jupiter was a small planet. However, it turned out to be a never-before-seen category of star, as it was much smaller in size than the average planet.
The asteroid in question was Ceres, the largest ever detected by humans, with approximately 950 kilometers in diameter. New observations, however, have shown that Ceres has distinct characteristics from other asteroids. At the beginning of the 21st century, after 150 years of being considered an asteroid,
Ceres came to be classified as a dwarf planet.The known region of the Solar System that has the most asteroids is known as the Asteroid Belt, and is located between the orbits of the planet Mars and Jupiter.
There are two main theories about the existence of the Asteroid Belt:
- Fragments of larger celestial bodies that collided and formed smaller pieces;
- Fragments of planets that, for unknown reasons, during the early days of the Solar System, did not form;
After the 1990 Spelling Agreement, the correct spelling is asteroid, without the acute accent.
Near Earth Asteroids
Because of the gravitational shape of the planets or even the Sun, asteroids can be "hurled" in other directions, hitting planets, moons or even the sun.
According to the NASA - National Aeronautics and Space Administration (National Administration of Aeronautics and Space, in Portuguese), so that there is a probable collision of an asteroid with the Earth, this must be over 150 meters in diameter and pass less than 20,000 kilometers away from the planet.
the asteroid Apophis it is considered one of the most dangerous to terrestrial life. The big concern is due to its size (about 270 meters in diameter) and the collision course with the Earth, predicted for before the year 2036. The chances of Aposhis reaching the planet are small, however the data predicts that the object will pass at most 29 thousand kilometers away from Earth.
See also the meanings of Universe, Solar system, NASA and Galaxy.