What is Asteroid Belt? | Main Asteroid Belt

Asteroid Belt

                In 1596, Johannes Kepler analysing data of Tycho Brahe’s, Kepler thought that there was too large gap between the orbits of planet Mars and Jupiter. According to Titius-Bode Law an apparent pattern in the layout of the planets, one planet is missing between the orbits of Mars and Jupiter. In 1781, the William Herschel discovered the planet Uranus. The planet’s orbit matched the Titius-Bode Law almost perfectly. In January 1, 1801, Chair of astronomy at the University of Palermo, found a tiny moving object in an orbit which is exactly predicted by the pattern. This object is the Ceres. The Ceres is the biggest asteroid in the main asteroid belt which was categorized as “Dwarf Planet”. The Heinrich Olbers found a second in the same region where the Ceres was found, Pallas. After the further investigation, the astronomer discovered two new objects in the same region named as Juno and Vesta. These four asteroids Ceres, Pallas, Juno and Vesta are half the mass of the asteroid belt. The predicted mass of the asteroid belt is nearly 4% that of the Earth’s moon.

                The asteroid belt consists of many large asteroids. There are 16 in the belt with diameter greater than 150 miles. The four largest asteroids are known in main asteroid belt. These are the Ceres (Dwarf Planet), Pallas, Juno and Vesta. Most of the asteroids are not massive enough to be spherical shape. They are of irregular shaped. These asteroids are composed of rocky-metallic materials. Astronomer discovered the group of asteroids orbiting across orbit of Earth. This group of asteroids are known as “Near-Earth Asteroids”. The current theory suggests that the main asteroid belt was more populated, but because of the gravitational pull of planet Jupiter flung of its former material to other places of solar system and beyond. The gravity of Jupiter flung approximately 99 percent of material. According to the assumptions of astronomers, the gravity of Jupiter prevents the materials of asteroids to form a planet. As like the dwarf planet Ceres.

                In early years of the solar system, the dust and rocky materials are orbiting around the Sun. the gravity pulled materials together to form the planets. But the region between the orbits of the Mars and Jupiter, the remaining materials which are not integrated together. But one assumption of astronomers about the formation of asteroid belt is, the asteroid belt is nothing but the remains of the destroyed planets. The asteroid belt is torus shaped region situated between orbits of Mars and Jupiter planets. The asteroids are sometimes called as Minor Planets. The asteroid belt is the dividing line between the inner rocky planets and outer gas giants the Jupiter.

                The asteroid belt is 140 million miles wide orbiting the Sun. In the Hollywood movies, the asteroid belt is shown heavily populated. But in the real time, many spacecraft have safely traveled through it without any incidence. That means, the asteroids are not too closer to each other. The gaps are big enough to pass any spacecraft without any collision. The gaps between the asteroids is called as “Kirkwood Gaps”. These were created by the gravitational pull of gas giant Jupiter.

                The composition of asteroids is determined by how the asteroids are close to the Sun. The asteroids which close to the Sun are composed with carbon and small traces of Oxygen, Hydrogen, Nitrogen. And the asteroid which further away from the Sun are composed mainly with the silicate rock.

                The asteroids are mainly classified by the composition into three categories. The C-type asteroids, the S-type asteroids and the M-type asteroids.

C-type asteroids:

                These type of asteroids are the most ancient objects in our solar system. These asteroids are very dark in appearance and consists of silicate rock and clay. The C-type is known as chondrite asteroids. These asteroids are most common and making up about 75% of known asteroids. These asteroids are mainly in outer regions of the asteroid belt. The chondrite or carbonaceous asteroids are composed with large amount of carbon and small amount of minerals and rocky materials. The C-type asteroids are sub classified in three sub groups B-type, F-type and G-type. The most massive asteroid is G-type asteroid and G-type asteroid is the sub group of C-type asteroid. So, the most massive asteroid in the main asteroid belt, the Ceres dwarf planet is the C-type (G-type sub group) asteroid. These asteroids are the most numerous asteroids in our solar system. Because of low albedo of 0.03 makes them very difficult to observe. These asteroids have survived for millions of years. On day this entire asteroid belt will be gone. When the Sun approaches the end of its life. The Sun’s radiation will shatter the asteroids.

S-type asteroids:

                The S-type asteroids are mainly composed with of magnesium silicates (stony) material, nickel-iron. The albedo of S-type asteroids is higher than that of C-type asteroids. The albedo is 0.20. So, they are moderately bright asteroids. These types of asteroids are found at the inner region of the asteroid belt and spread up to the centre of the belt. The S-type asteroids are sub classified as A-type, K-type, L-type, Q-type and R-type. Approximately 17% of the asteroids are of this types. This percentage making it the second most common asteroids after the C-type (carbonaceous) asteroids. The colour of the S-type silicaceous asteroid are greenish to reddish.

M-type asteroids:

                The M-type metallic asteroids composed of nickel-iron either pure or mixed with small amount of stone. The albedo of these types of asteroids between 0.1 to 0.2, making them moderately bright asteroids. The M-types are located at the middle of the asteroid belt. The M-type are third most common type of asteroids in our solar system, but they are the least studied asteroids type in our solar system.

Trojan Asteroids

                The Trojan is a small celestial body mainly the asteroid. This small body shares the orbit of the largest planet in our solar system the Jupiter. The Trojan asteroids are discovered by German astronomer Max Wolf in 1906. The asteroids group is named from Greek mythology after a figure of the “Trojan War”.

Trojan Asteroids of the Jupiter

                In 1770, the French mathematician and astronomer Joseph Louis Lagrang discovered the location and existence of the two groups of asteroids. These two groups of asteroids are gravitationally stable points located near the orbit of the Jupiter. These asteroids are remaining in the stable orbit approximately 60^O ahead and behind the Jupiter. These points are Lagrangian points L₄ and L₅. These two points was named after the astronomer and discoverer of these points Joseph Louis Lagrang, as Lagrangian point and designated as L₄ and L₅. The astronomers discovered more than 7000 Trojan asteroids by 2020. In that more than 7000 discovered Trojan about two-third are located near L₄ point, and remaining are near L₅ point. According to observations of astronomers, 1800 to 2200 of the total existing number of the Jupiter’s Trojan have diameter greater than 15 km (10 miles).

Near-Earth Asteroids

                The Near-Earth Asteroids (NEAs) are defined as all small solar system bodies with orbits around the Sun that lie partly between 0.98 and 1.3 AU away from the Sun. These asteroids are not necessarily currently near the Earth, but they can approach the Earth relatively closely. Asteroids are as small as 20 meters (66 ft) in diameter but still they can cause significant damage to the human population.

Near-Earth Asteroids

The Near-Earth objects are classified as Meteoroids, asteroids and comets. Depending on size, composition and orbit. The Near-Earth asteroids are asteroids in a near Earth orbit without tail or comet’s coma. These asteroids are sufficiently large and sufficiently close to Earth to be considered potentially hazardous.