There are a large number of asteroids found in the solar system. Most of them circle the sun in the same manner as planets do. Some of them may circulate around the nearest planet, too. The asteroids are rock-like in appearance and contain different minerals. They are believed to be created by the Big Bang that occurred when the stars and planets came into being. The origin of asteroids is believed to have occurred almost 13.7 billion years ago. There are at least 1,113,527 asteroids in the solar system today. Vesta is the largest of them with a diameter of 530 kilometres, while the smallest measures less than 10 metres across. The combined mass of all known asteroids today is far less than that of earth’s satellite, i.e. the moon. The asteroids are rich in minerals and space missions like ISRO and NASA are contemplating mining them to retrieve large amounts of nickel, iron, and other elements/metals.

How are Asteroids named?

The first few asteroids were discovered in the 19th century. William Herschel first used the term. The scientists began to refer to asteroids as “minor planets” by 1802. The practice of attributing names to different asteroids was discontinued in 1851 with the newly discovered rocks designated a number instead of names. This particular rock is now known both as an asteroid and a dwarf planet. It is the “International Astronomical Union (IAU)” that deals with the naming of celestial bodies including stars, planets, and asteroids. The body has become less strict about the naming process at present. Collectively known as “star rocks,” there are many asteroids named after fictional characters, musicians, and the crew of the doomed Space Shuttle Columbia. The IAU has discontinued the practice of naming asteroids after pets.

Asteroid Types

Asteroids are primarily found in the asteroid belt seen between Mars and Jupiter. Three of the biggest asteroids are sphere-like in shape, however, with their composition differing greatly. They form three distinct groups based on the chemicals inside.

1. C-Type: Contains carbon compounds predominantly and appears dark. Almost 75% of all asteroids belong to this category.
2. S-Type: These contain silicates of iron and magnesium. Such asteroids are a trifle brighter and usually found in the inner asteroid belt.
3. M-Type: This category of asteroids contains nickel and pure iron.

Classification of Asteroids

• Asteroid Belt- The maximum number of known asteroids is found between Mars and Jupiter in the solar system. They circle their respective planets or the sun, as they continue to revolve along their orbits. The belt includes 1.1 to 1.9 million asteroids that are relatively bigger (0.6 miles diameter). It also contains millions of smaller asteroids circling the planets as space debris. According to space history, the strong gravitational force of planet Jupiter caused multiple smaller rocks to collide and coalesce to form asteroids. There are no more rocky formations observed in the region at present.
• Trojan- These are smaller asteroids that share the same orbit as the nearby planet. The possibility of a collision is avoided by the presence of L4 and L5 Lagrangian points on the orbit itself. The asteroids remain confined to these points. The Sun’s gravity coupled with the pull of the concerned planet holds the Trojan steady. Otherwise, it tends to move out of orbit and fly into the vast space beyond. Jupiter has the highest number of Trojans, while Mars and Neptune contain a substantial number too. NASA had also discovered an Earth Trojan in 2011.
• Near-Earth Asteroids (NEA)- These rocks move along orbits that pass very near the Earth. The objects that pass across Earth’s orbit are known as, “Earth Crossers.”

Other Space Rocks

• Comets-These are rocks that circle the sun too. However, it is better to term them as snowballs instead of rocks. They consist of an icy nucleus made of frozen gases. The comets are believed to be created by the big bang too. A comet may become a glowing mass of fire when it approaches the sun. The gigantic tails are often visible from the earth.
• Meteors-The fragmented space rocks created by the collision of asteroids, comets, satellites, and planets are termed meteorites. They are considered to be the smallest rocks in space. The main difference between an asteroid and a meteor is that the latter falls in the form of meteorites. The specks of dust-like particles reach the earth at a great speed, causing a fiery glow that lights up the sky. A meteorite shower is thus a celestial event of interest for people around the world. It is frequently referred to as a shooting star. Scientists have found a combination of metals and rocks in the meteors. There are 48.5 tons of meteorite material falling on earth every day, reveals NASA scientists.

Difference Between Asteroid And Meteor

Conclusion

Asteroids are heavenly bodies found in different areas of the solar system. They have a mass much less than that of a planet. Termed as minor planets, they differ sharply from planets, comets, and meteorites.  They are believed to have formed billions of years ago with the creation of the Universe. Each asteroid is different, with some of them circling the closest planet instead of the sun. There are more than 1,113,527 in the solar system at present. Many are found in the asteroid belt located between Mars and Jupiter. They contain a rich deposit of various metals and minerals.