The solar system is the planetary system composed of the Sun and the celestial elements that are held together with the Sun by gravity. The Sun is a G2-class main sequence star measuring 1.39 million kilometers in diameter. The Sun represents 99.86% of the mass of the solar system and is the closest star to Earth.
The solar system is located in the Local Interstellar cloud, located in the Local Bubble of the Orion arm, within the Milky Way . The Milky Way is between 150 and 230 thousand light years in size and has between 100-400 billion stars. For reference, there is no planet in our solar system that is more than one light year from the Sun.
In the space between these celestial bodies is interplanetary matter. According to one definition, the solar system is bounded by the heliopause, the edge of the heliosphere.
Features of the solar system
The solar system is unique in the cosmos due to a number of distinctive features that differentiate it from other star systems and celestial objects in the universe. These features include:
- The central star of the solar system, the Sun, is a yellow dwarf star of spectral type G2V.
- Size of the Sun (average diameter): Approximately 1.4 million kilometers (109 times the diameter of the Earth).
- Number of planets: 8, which are a mix of terrestrial planets (Mercury, Venus, Earth and Mars) and giant planets (Jupiter, Saturn, Uranus and Neptune).
- Earth is the only known celestial body that supports life.
- Number of dwarf planets recognized: 5 (Pluto, Eris, Makemake, Haumea and Ceres).
- Number of moons in the Solar System: More than 200 known moons.
- Average Distance from Earth to the Sun (Astronomical Unit - AU): Approximately 149.6 million kilometers (93 million miles).
- Size of Earth's Moon (average diameter): Approximately 3,474 kilometers (a little more than a quarter the size of Earth).
- Largest planet in the Solar System (by diameter): Jupiter, with a diameter of approximately 139.8 thousand kilometers.
- Smallest planet (by diameter): Mercury, with a diameter of approximately 4,880 kilometers.
- Number of main planetary rings: Saturn has at least 83 main rings.
- Known comets: Thousands of comets, although the precise number is difficult to determine.
- Asteroids in the Asteroid Belt: There are more than 1.1 million cataloged asteroids, although there are many smaller uncatalogued ones.
- Distance from Pluto to the Sun (in AU): Variable due to its elliptical orbit, but on average is approximately 39.5 AU (about 5.9 billion kilometers or 3.67 billion miles).
Components of the solar system
In addition to the Sun, the Solar System contains eight planets, five dwarf planets, more than one million known asteroids, 644 moons of planets, dwarf planets and asteroids, and 3,701 known comets. Most of these objects orbit the Sun in orbits with small inclinations relative to the ecliptic.
Most of the large elements orbiting the Sun move in the same virtual plane, called the ecliptic plane.
The Sun, the central star of the Solar System
The sun contains by its attraction all the planets of the solar system that orbit around it; in addition to other bodies that belong to him.
It is a medium star but, due to its proximity, it is the only star whose circular shape can be seen with the naked eye.
The Sun emits energy in the form of radiation from the nuclear fusion reactions of hydrogen atoms that occur inside it. This energy is vital for life, since it allows us to maintain the Earth in temperature ranges suitable for life and so that some base elements of the food chain can carry out photosynthesis.
It is estimated that the Sun formed about 5 billion years ago and is in the middle of its life.
Planets of the solar system
The solar system includes:
-
Terrestrial planets: Mercury, Venus, Earth, Mars.
-
Giant planets: Jupiter, Saturn, Uranus, Neptune
All the planets and most elements of the solar system revolve around the Sun in the same direction that our central star rotates (counterclockwise when viewed from the Sun's North Pole).
Most planets rotate around their axis in the same direction as they rotate around the Sun with the exceptions being Venus and Uranus.
The orbits of objects around the Sun are described by Kepler's laws. According to them, each object rotates on an ellipse, at one of whose focuses is the Sun.
Satellites of planets and moons
The four largest planets are gas giants. These planets also have rings, thin bands of small particles that rotate in very close orbits almost in unison.
Tiny planets
A dwarf planet is a spherical object that moves in a heliocentric orbit, but has not cleared the surrounding space.
Here is the list of some of the recognized dwarf planets in the solar system:
-
Pluto is perhaps the best-known dwarf planet and was considered the ninth planet in the solar system until 2006.
-
Eris is the largest known dwarf planet in the outer solar system. It was one of the objects that contributed to the redefinition of Pluto as a dwarf planet due to its similar size.
-
Makemake is another dwarf planet in the Kuiper Belt and is known for its extremely cold and bright surface.
-
Haumea is a dwarf planet in the Kuiper Belt with an unusually elongated shape due to its rapid rotation.
-
Ceres is the largest dwarf planet in the Asteroid Belt, located between Mars and Jupiter.
Minor bodies
A minor body in the solar system is a celestial body that orbits the Sun and is neither a planet, nor a dwarf planet, nor a satellite. Minor bodies of the solar system include: asteroids (small planets), meteorites and meteorite bodies, comets.
The minor bodies of the solar system are grouped into:
-
Asteroid belt.
-
Trans-Neptunian objects and the Kuiper Belt.
-
Oort cloud.
Origin of the solar system
According to modern thinking, according to the theory of the Solar Nebula, the Solar System was formed about 5 billion years ago as a result of the accumulation and compression by gravity of a cloud of gas dust.
Due to the rotation, the compression velocities of the clouds parallel and perpendicular to the axis of rotation were different, which caused the flattening of the cloud and the formation of a characteristic protoplanetary disk and a dense, hot protostar in the center. The planets were formed by accretion of this disk.
Within 50 million years, the pressure and density of hydrogen in the center of the protostar became high enough to initiate a nuclear fusion reaction of hydrogen atoms. This nuclear energy is the origin of solar energy.
As the Sun burns through its hydrogen fuel reserves, the energy released to sustain the core tends to be depleted, causing the Sun to contract. This increases the pressure inside and heats the core, thus accelerating the combustion of the fuel.