We explain what asteroids are, types of asteroids, where they come from, their classification and other characteristics. In addition, differences with comets.
What is an asteroid?
An asteroid is a type of space rock, much smaller than a planet , and moves in an elliptical orbit around the sun . There are millions of asteroids and most of them are in the so-called ” asteroid belt “. The rest is distributed in the orbital path of other planets in the Solar System , including Earth.
Asteroids are a reason for constant study due to the proximity they maintain with the Earth. The odds of impact are very low despite the fact that in the very remote past they have reached our planet . In fact, many scientists attribute the disappearance of dinosaurs to the impact of an asteroid.
The asteroid name comes from the Greek meaning “stellar figure” and refers to its appearance since, when viewed with a telescope from Earth, they look like stars . For much of the nineteenth century, asteroids were called “planetoids” or “dwarf planets.”
Where do asteroids come from?
The hypothesis argues that asteroids are remains of the cloud of gas and dust that condensed about five million years ago , when the Sun and Earth formed. Some of the matter derived from that cloud gathered in the center and formed a nucleus that gave rise to the Sun.
The rest of the matter, which revolved around the new core, formed pieces of different sizes called “planetesimals.” The asteroids come from part of that matter that was not incorporated into the Sun or the planets of the Solar System.
Types of asteroids
Asteroids are classified into three groups, according to their location and type of grouping:
- The asteroids of the asteroid belt. They are those that orbit in the space or border, between Mars and Jupiter. The belt conglomerates most of the asteroids of the Solar System.
- Centaurus asteroids. They are what they orbit on the border between Jupiter or Saturn, and between Uranus or Neptune , respectively.
- The Trojan asteroids. They are the ones that share the orbit of a planet , but they don’t usually impact.
The asteroids that are closest to our planet are subdivided into three types:
- The asteroids Love. Those who cross the orbit of Mars.
- Apollo asteroids. Those who cross the Earth’s orbit and are therefore a relative threat (despite the low risk of impact).
- The asteroid Aton. Those who partially cross the Earth’s orbit.
Asteroids are characterized by having a very weak gravitational force , which does not allow them to reach a completely sphere shape. Its diameter can vary from a few meters to hundreds of kilometers.
They are composed of metals and rocks (clay, silicate and nickel-iron rocks) whose proportions can vary according to each type of celestial star . They have no atmosphere and some have at least one satellite.
From the earth’s surface, asteroids look like small points of light, as if they were stars. Due to their small size and great distance from Earth, what is known about them was obtained based on astrometric and radiometric measurements, light curves and absorption spectra (astronomical calculations that allow us to know much of our Solar System).
Difference Between Asteroid And Comet
Asteroids and comets have in common that they are celestial bodies that orbit the Sun , that they usually make unusual paths (such as approaching the Sun or other planets) and that they are remnants of the matter that gave rise to the Solar System.
However, they differ in that comets are composed of dust and gases and, in addition, of ice particles . Comets are known for the tail or wake they leave behind, although they don’t always leave a trace.
Containing ice, its state and appearance vary according to the distance from the Sun: they are very cold and dark when they are far away, or they heat up and expel dust and gas (hence the origin of the tail trail) when they approach the Sun It is believed that comets may have deposited water and other organic compounds on planet Earth when it was just forming.
There are two types of kites:
- Short period Those comets that take less than two hundred years to complete an orbit around the Sun.
- Long period. Those comets that make long and unpredictable orbits. It may take up to thirty million years to complete a round around the sun.
The asteroid belt consists of the union or the approximation of several celestial bodies distributed in the form of a ring (or belt), located between the border of Mars and that of Jupiter.
It is estimated that it has about two hundred large-sized asteroids (with a diameter of one hundred kilometers) and almost one million small-sized asteroids (with a diameter of one kilometer). Due to the size of the asteroids, there are four that were identified and that stand out:
- Ceres It is the largest in the belt and the only one that was very close to being considered a planet because of its rather well defined sphere shape.
- Vesta It is the second largest asteroid in the belt, the one with the highest mass and the one with the highest density . Its shape is flattened spheroid.
- Pallas. It is the third largest in the belt and its orbit is slightly inclined, something particular for a body of its size.
- Higia It is the fourth largest in the belt, with a diameter of four hundred kilometers. Its surface is very dark, which makes it difficult to identify it.