The Solar System Explained in Simple Terms

The solar system is located approximately 24,000 to 27,000 light-years from the center of the Milky Way. (The Milky Way contains between 100 billion and 400 billion stars, of which the Sun is just one.) The Sun orbits the galactic center at a speed of 220 km/s, completing one orbit every 250 million years. This causes Earth's climate and the natural world to undergo a 250-million-year cycle. The Sun's orbit is generally oriented toward the constellation Vega, near Hercules.

As of October 2019, the solar system consists of the Sun, eight planets, nearly 500 satellites, and at least 1.2 million asteroids. There are also several dwarf planets and comets. If the orbit of Neptune is used as the boundary of the solar system, the diameter of the solar system is 60 astronomical units, or about 9 billion kilometers. If the heliosphere is used as the boundary, the Sun is as far as 100 astronomical units from the boundary (at its thinnest point). If the Oort Cloud is used as the boundary, the diameter of the solar system may be 200,000 astronomical units. Solar System Concept
The solar system began to form approximately 4.6 billion years ago with the gravitational collapse of a massive interstellar molecular cloud. Most of the solar system's mass is concentrated in the Sun, with Jupiter being the most massive of the remaining celestial bodies. The eight planets orbit the Sun counterclockwise. In addition, smaller bodies exist in the asteroid belt between Jupiter and Mars. Numerous small bodies also exist in the Kuiper Belt and the Oort Cloud. Many satellites orbit planets and small bodies. Each planet outside the asteroid belt has rings.
The Sun is the central body of the solar system, accounting for approximately 99.86% of the total mass of the solar system. It is a medium-sized yellow dwarf star composed primarily of hydrogen (about 74%) and helium (about 24%). It generates energy through nuclear fusion reactions. The Sun's gravity causes all other celestial bodies to orbit it, while also providing them with light and heat.

Structure of the Sun
The Sun's internal structure is divided into several layers:
  • Core: This is where nuclear fusion reactions occur, reaching temperatures as high as 15 million degrees Celsius. Radiative zone: The region where energy is transferred from the core outward, where photons can take hundreds of thousands of years to traverse.
  • Convective zone: Here, heat is transferred by convection, generating the phenomena on the Sun's surface.
  • Photosphere: The surface of the Sun visible to the naked eye, with a temperature of approximately 5,500 degrees Celsius.
  • Chromosphere: The thin layer of gas above the photosphere, with temperatures reaching tens of thousands of degrees Celsius.
  • Corona: The Sun's outer atmosphere, with temperatures reaching millions of degrees Celsius, generates the solar wind that influences the entire solar system.
Planets
There are eight planets in the solar system. In order of distance from the Sun, they are:
  • Mercury: The smallest planet, with almost no atmosphere and extremely variable surface temperatures.
  • Venus: Similar in size to Earth, but with a thick carbon dioxide atmosphere, extremely high temperatures, and sulfuric acid clouds on its surface.
  • Earth: The only planet known to support life, with a suitable temperature and the potential for liquid water.
  • Mars: Known as the "Red Planet," it has polar ice caps and dry riverbeds, suggesting the possibility of water in the past.
  • Jupiter: The largest planet, with a powerful gravity and a rich satellite system. Its famous Great Red Spot is a persistent storm.
  • Saturn: Famous for its spectacular rings, composed of ice and rock particles, and numerous satellites.
  • Uranus: A sideways-rotating planet with extremely low surface temperatures and a distinctive blue appearance.
  • Neptune: The farthest planet, with intense storms, a beautiful blue color, and extremely low surface temperatures.

Planet Classification
The solar system's planets can be divided into two categories based on their properties:
  1. Terrestrial planets: Mercury, Venus, Earth, and Mars, are primarily composed of rock and metal, with hard surfaces.
  2. Giant planets: Jupiter, Saturn, Uranus, and Neptune, are primarily composed of gas and ice, and are large and heavy.
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