As intriguing as it is fascinating, the solar system still hides many secrets from us. However, thanks to major technological advances made by humans, we learn a little more every day about this astonishing phenomenon essential to our survival. Let's discover together what elements make up the solar system and how it works.
What is the solar system made of?
The solar system is a planetary system to which Earth belongs. It is part of the galaxy, commonly called the Milky Way. It consists of a star which is none other than the Sun, as well as celestial objects that revolve around it. These orbiting objects are actually the 8 major planets we know: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, accompanied by their 205 natural satellites, nicknamed "moons", as well as five dwarf planets and their 9 natural satellites. Finally, the entire solar system also includes billions of small bodies such as comets, asteroids, interplanetary dust, and minor planets.
The Sun: the major star of the solar system
The Sun is a spectral type star located approximately 150 million kilometers from Earth. Despite this distance, it is the closest star to our planet! Essential to our life on Earth, solar energy is produced by nuclear reactions taking place in the Sun's core. Its mass represents the major part of the solar system's mass. The Sun is approximately 5 billion years old and experts estimate that its luminosity will slowly increase for an equivalent duration before becoming a "red giant": this is a very large and highly luminous star that has undergone gravitational collapse. When it reaches this stage of transformation, the Sun will die.
Thanks to the movements the Sun makes relative to the Earth, the seasons were born. It was Galileo who discovered in 1611 that the Sun rotates on its own axis for a duration of 27 days. Finally, the Sun is divided into several layers including the core, the radiative zone, the convection zone, the photosphere in charge of emitting most of the solar light, the chromosphere and its outer part, and its corona.
Mercury: the smallest planet in the solar system and the closest to the Sun
Mercury is barely larger than the Moon and is 20 times less massive than Earth. Its surface is almost devoid of atmosphere and the sunlight there is seven times more intense and brighter than on Earth. Brownish-grey in color, the absence of an atmosphere on this planet means that many asteroids crash into it, leaving large craters similar to those found on the far side of the Moon. There are also incredible cliffs hundreds of kilometers high that formed following the cooling and contraction of the planet's interior after its formation. In its shaded areas protected from sunlight, Mercury is believed to possess water ice, particularly at its North and South poles.
Moreover, Mercury is the fastest planet in the Solar System. It only needs 88 days to orbit the Sun and is capable of moving at 47 kilometers per second. Mercury is a terrestrial planet, composed of a core, a mantle, and a crust. After Earth, it is the second densest planet thanks to its imposing metallic iron and nickel core, representing a partially liquid radius of over 2,000 km.
Venus: the second planet in the Solar System by distance from the Sun
The planet Venus owes its name to the Roman goddess of love. It is the sixth largest planet in the Solar System, both by its mass and its diameter. Venus orbits the Sun every 224.7 days. It needs 243 days to complete one rotation on its axis, which is much longer than any other planet in the Solar System. Like Uranus, Venus has a retrograde rotation and therefore spins in the opposite direction to that of other planets. Thus, the Sun rises in the west and sets in the east. It has no natural satellites and is almost spherical due to its slow rotation.
Like Mercury, Venus is one of the four terrestrial planets in the Solar System. Its magnetic field is very weak, and it has an atmosphere much denser than Earth's, as it is composed of more than 96% carbon dioxide. Its atmospheric pressure is therefore equivalent to the pressure felt 900m underwater on Earth. It is the hottest planet in the Solar System, with a temperature of approximately 462°! Venus is enveloped in an opaque layer of sulfuric acid clouds, preventing its surface from being seen from space. It appears as a dry, rocky, and desert-like planet whose landscapes resemble volcanic landscapes. Finally, with very few elevated reliefs, it is composed mainly of vast plains that are geologically very young, estimated to be only a few hundred million years old.
Earth: the only planet capable of supporting life
Also called the blue planet, Earth is also one of the four terrestrial planets. Its creation is estimated to be 4.54 billion years ago. It is the third planet from the Sun and the fifth largest in the Solar System. To orbit the Sun, it needs 365 days and it is capable of completing a rotation on itself relative to the Sun in 23 hours 56 minutes. Earth has a single natural satellite: the Moon. The first traces of life on Earth come from the oceans, at least 3.5 billion years ago. Its axis of rotation has an inclination of 23°, which is the origin of the appearance of seasons!
Its atmosphere, ozone layer, magnetic field, and geological evolution are at the heart of the life cycle: these factors allow us to live on this planet. Throughout its evolutionary history, biodiversity has experienced long periods of expansion, punctuated by mass extinctions: approximately 99% of the species that once lived on Earth are now extinct. In 2020, Earth is home to over 7.7 billion human beings. We depend entirely on its biosphere and its natural resources for survival.
Earth is the densest planet in the Solar System, as well as the largest and most massive of the four terrestrial planets. 71% of its surface is covered with water, divided into oceans, lakes, and rivers. The remaining 29% are continents and islands.
Mars: The one nicknamed the Red Planet
Mars is the last terrestrial planet alongside Mercury, Venus, and Earth. It is the fourth planet in increasing order of distance from the Sun and the second in increasing order of size and mass. Thus, it is ten times less massive than Earth, but ten times more massive than the Moon. Mars has great similarities with Earth, as it features tectonic and climatic formations such as volcanoes, valleys, dunes, and polar ice caps. It also shares similarities with the Moon in terms of its craters and impact basins. The highest volcano ever discovered in space, Olympus Mons, as well as the largest Canyon, Valles Marineris, are both found on Mars.
Today, Mars has lost almost all of its geological activity. Only minor events would still occur episodically, such as landslides, CO2 geysers in the polar regions, earthquakes, or rare volcanic eruptions leading to slight lava flows.
Almost twice smaller than Earth, the planet known as the Red Planet consists of a solid body with a 50-kilometer-thick crust, a lithosphere about 150 to 200 kilometers thick, and a core with a radius of 1700 kilometers. Finally, the atmosphere of the planet Mars mainly contains carbon dioxide (CO2), which represents 95.32% of its composition.
Jupiter: The first gas giant planet
Jupiter owes its name to the Roman god of the same name. It is the largest planet in the Solar System, as it is more massive and voluminous than all other planets combined! Jupiter is also the fifth planet in terms of its distance from the Sun. Jupiter is said to be a gas giant planet because it is mainly composed of hydrogen (97%) and helium (7%).
Jupiter is home to violent winds reaching 600 km/h, due to its gaseous environment. In the 20th century, it was three times larger than Earth, but it has since shrunk to now reach a comparable size. It has a unique specificity called "the Great Red Spot": it is a persistent anticyclonic storm on its surface. Its existence has been known since at least 1831, making this storm a permanent feature of the planet. From Earth, it is notably possible to observe this incredible red spot with a telescope to see the storm!
Saturn: The second gas giant planet
The sixth planet in the Solar System by distance from the Sun, Saturn is also the second largest planet in size and mass after Jupiter. It is also a gas giant planet. Known for its incredible rings, this planet is mainly composed of ice particles and dust. Saturn is the planet with the largest number of natural satellites, with more than 82 detected, as well as hundreds of minor satellites.
Saturn is a planet composed of a rocky core of silicates and iron, surrounded by layers of hydrogen (96%) in various forms: metallic, liquid, and then gaseous, all mixed with helium. Thus, Saturn has no solid surface and is the planet with the lowest average density.
Finally, Saturn has been known since prehistoric times. Its observation by ancient civilizations inspired numerous myths. It is named after the Roman god of agriculture (comparable to Cronus in Greek mythology) and its astronomical symbol represents the god's sickle.
Uranus: The first ice giant planet
Uranus is the seventh planet in the Solar System in order of distance from the Sun. It is the fourth most massive planet in the Solar System and the third largest in size. It was first observed through a telescope by William Herschel in 1781, making it the first planet to be discovered in the modern era. Like Jupiter and Saturn, Uranus is primarily composed of hydrogen and helium, as well as traces of hydrocarbons. The interior of this planet is also composed of ice and rocks, hence its nickname as an ice giant planet. Uranus is aquamarine in color because methane gives it this color, as well as the water and ammonia found there.
Uranus's planetary atmosphere is the coldest in the solar system: it can reach as low as -224°C! This planet has a ring system as well as numerous natural satellites: 13 rings and 27 moons have already been detected.
Neptune: The second ice giant planet
Neptune is the eighth and last planet in the Solar System. This planet is 17 times more massive than Earth and 19 times less massive than Jupiter. It was not until the invention of the telescope that Neptune was discovered because it is invisible to the naked eye. However, its discovery is all the more particular because suspicions about its existence arose with the help of a mathematical formula, long before the invention of the telescope, which in reality only served to confirm this discovery.
Like its sister Uranus, Neptune's atmosphere is mainly composed of hydrogen and helium, as well as traces of hydrocarbons. There may also be traces of nitrogen, but this is still difficult to confirm. This makes Neptune an ice planet. It is therefore a deep blue color and its climate can reach -218°C!
We hope this article about the 8 planets in the solar system has taught you many things and that it has taken you on a journey through space! Leave us a comment to tell us which planet is your favorite and which one you would like to visit.
