Welcome to our exploration of the solar system. Our solar system consists of the Sun at its center, and everything bound to it by gravity. This includes eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. The solar system also contains dwarf planets like Pluto, numerous moons orbiting the planets, asteroids, comets, and cosmic dust. All these objects are held in orbit around the Sun by its gravitational pull.
At the center of our solar system is the Sun, a G-type main-sequence star. The Sun contains 99.86% of the total mass of the solar system. It has a diameter of about 1.4 million kilometers, which is 109 times the diameter of Earth. The Sun's surface temperature is approximately 5,500 degrees Celsius, while its core reaches an incredible 15 million degrees Celsius. This extreme heat in the core enables nuclear fusion, where hydrogen atoms combine to form helium, releasing enormous amounts of energy in the process. This energy radiates outward through the Sun's layers, including the visible surface called the photosphere, and the outer atmosphere known as the corona, which can be seen during a total solar eclipse.
Our solar system contains eight planets that are divided into three categories. The inner or terrestrial planets include Mercury, Venus, Earth, and Mars. These are relatively small, rocky worlds with solid surfaces. Beyond them are the gas giants: Jupiter and Saturn. These massive planets are primarily composed of hydrogen and helium. Finally, we have the ice giants: Uranus and Neptune, which contain more ices such as water, ammonia, and methane in their composition. All planets orbit the Sun in elliptical paths and rotate on their axes at different rates. Earth completes one rotation in 24 hours, while Venus takes 243 Earth days to rotate once. Jupiter, despite being the largest planet, has the fastest rotation at just under 10 hours.
Beyond the eight planets, our solar system contains a diverse array of other celestial objects. Dwarf planets like Pluto, Ceres, and Eris are smaller bodies that orbit the Sun but haven't cleared their orbital paths of other objects. The solar system also includes over 200 moons or natural satellites orbiting the planets, with Jupiter and Saturn having the most. Between Mars and Jupiter lies the Asteroid Belt, home to millions of rocky bodies ranging from dust particles to the dwarf planet Ceres. Comets are icy bodies that develop distinctive tails when they approach the Sun. Beyond Neptune, we find the Kuiper Belt, a ring of icy bodies including Pluto and many other dwarf planets and smaller objects. Even further out is the theoretical Oort Cloud, a spherical shell of icy objects marking the boundary of our solar system's gravitational influence.
Our solar system is located in the Milky Way galaxy, a spiral galaxy containing hundreds of billions of stars. Specifically, we're positioned in the Orion Arm, about 26,000 light-years from the galactic center. The solar system formed approximately 4.6 billion years ago from a giant molecular cloud of gas and dust. It takes our solar system about 230 million years to complete one orbit around the Milky Way galaxy. This means that since the formation of our solar system, we've completed about 20 galactic orbits. The entire solar system is held together by the gravitational force of the Sun, which contains 99.86% of the system's total mass. This gravitational influence extends far beyond the planets to the distant Oort Cloud, marking the boundary of our solar system's reach.