Asteroid (Meaning and Explanation)

We explain what asteroids are, where they come from, their classification and characteristics. Also, differences with comets.

What is an asteroid?

an asteroid It 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 found 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 source of constant study due to their proximity to Earth. The chances of them impacting are very low even though in a very remote past they have reached our planet. In fact, many scientists attribute the disappearance of the dinosaurs to the impact of an asteroid.

The name asteroid It comes from the Greek meaning “stellar figure” and refers to their appearance since, when observed with a telescope from Earth, they look like stars. For much of the 19th century, asteroids were called “planetoids” or “dwarf planets.”

Where do asteroids come from?

The hypothesis holds that asteroids are remains of the cloud of gas and dust that condensed about five million years ago when the Sun and the Earth were formed. Part 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 nucleus, formed pieces of different sizes called “planetesimals”. 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, depending on their location and type of grouping:

The asteroids of the Asteroid Belt. They are those that orbit in space or border, between Mars and Jupiter. The belt conglomerates most of the asteroids in the Solar System.
The Centaur asteroids They are what orbit on the border between Jupiter or Saturn, and between Uranus or Neptune, respectively.
The Trojan asteroids. They are those that share the orbit of a planet, but do not usually impact.

The asteroids that are closest to our planet are subdivided into three types:

The asteroids Love Those that cross the orbit of Mars.
The Apollo asteroids. Those that cross the Earth's orbit and therefore are a relative threat (despite the low risk of impact).
The asteroids Aton. Those that partially cross the Earth's orbit.

Asteroid characteristics

The asteroids are characterized by having a very weak gravitational force which does not allow them to achieve 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 rocks and nickel-iron) whose proportions can vary according to each type of celestial body. have no atmosphere and some have at least one satellite.

From the Earth's surface, asteroids look like small points of light, like 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 (astronomic calculations that allow us to know a large part of our Solar System).

Asteroids and comets

comet asteroid — Comets are known for their wake.

Asteroids and comets have in common that they are celestial bodies that orbit around the Sun which usually take unusual paths (such as approaching the Sun or other planets) and which 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, ice particles. Comets are known for the tail or wake they leave in their wake, although they do not always leave a trail.

As they contain ice, their condition and appearance vary depending on their 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 get closer to 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. They can take up to thirty million years to complete one revolution around the Sun.

asteroid belt

The asteroid belt consists of the union or the approximation of several celestial bodies distributed in the shape of a ring (or belt), located between the border of Mars and Jupiter.

It is estimated that it has about two hundred large asteroids (with a diameter of one hundred kilometers) and almost a million small asteroids (with a diameter of one kilometer). Due to the size of 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 due to its fairly well-defined sphere shape.
Vesta. It is the second largest asteroid in the belt, the one with the greatest mass and the highest density. Its shape is a 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.
Hygia. It is the fourth largest in the belt, with a diameter of four hundred kilometers. Its surface is very dark, making it difficult to identify.