Uploaded October 2020 | Updated September 2026, 1 hour ago
Our solar system is one of many planetary systems orbiting a host star in the Milky Way Galaxy. By definition, the Solar System is a gravitationally bound system of the Sun and the objects that orbit around it. These objects include planets, dwarf planets, moons, and other smaller masses such as asteroids comets, and meteoroids. Our planetary system is named the "solar" system because our Star is named Sol, which is derived from the Latin word "solis," for Sun, so anything related to the Sun we refer to as "solar."
The solar system formed about 4.6 billion years ago. It contains a total of 8 celestial bodies orbiting around the Sun that are officially recognized as planets. The four planets closest to the Sun-Mercury, Venus, Earth, and Mars — are called the terrestrial planets because they have solid, rocky surfaces. Two of the outer planets beyond the orbit of Mars — Jupiter, and Saturn — are known as gas giants. The more distant planets, Uranus and Neptune are called ice giants. Let’s take a closer look at each of these celestial bodies starting with the Sun.
The central star of our Solar System is the Sun with a mass of about 1.1x10^30 kg. It is large enough to fit about 1 million Earth inside its massive body and is the closest star to Earth, at an average distance of about 150 million kilometers (or 93 million miles). The Sun is mostly composed of ionized gas with 92.1% hydrogen, 7.8% helium, and 0.1% other elements that are held together by gravitational attraction, producing immense pressure and temperature at its center. It is divided into six regions, the core, the radiative zone, the convective zone, the photosphere, the chromosphere, and the corona. The temperatures at the core of the Sun can reach up to 15 million degrees Celsius (or 27 million degrees Fahrenheit) causing thermonuclear fusion and releasing huge amounts of energy powering the Sun. It takes around 170 000 years for this energy to reach the convective zone from the core due to the energy bouncing around in the radiative zone. Temperatures in the convective zone are about 2 million degrees Celsius (or 3.5 million degrees Fahrenheit) where large bubbles of hot plasma rise upwards. The photosphere or the visible surface of the Sun is a 500-km- thick (or 300-mile-thick) region from where most of the radiation escapes. It takes about 8 minutes for this radiation to reach Earth which we perceive as sunlight. The temperatures at the photosphere can reach about 5500 degrees Celsius (10 000 degrees Fahrenheit) with some areas having strong magnetic fields and being relatively cooler than the rest of the surface. These areas are called sunspots and are mostly darker than the surrounding regions. Above the photosphere are the chromosphere and the corona. These regions are usually outshined by the photosphere making them difficult to see. However, during a total solar eclipse, the chromosphere can be seen as a red rim around the Sun while the corona forms a beautiful white crown with plasma jetting outward. These massive coronal ejections blasting off the Sun are also known as solar flairs with temperatures reaching, quite surprisingly, up to 2 million degrees Celsius (or 3.5 million degrees Fahrenheit). Our Sun is the most important part of our solar system, providing energy and supporting life on Earth. Without the Sun, life as we know it, simply wouldn’t be possible.
Our solar system is one of many planetary systems orbiting a host star in the Milky Way Galaxy. By definition, the Solar System is a gravitationally bound system of the Sun and the objects that orbit around it. These objects include planets, dwarf planets, moons, and other smaller masses such as asteroids comets, and meteoroids. Our planetary system is named the "solar" system because our Star is named Sol, which is derived from the Latin word "solis," for Sun, so anything related to the Sun we refer to as "solar."
The solar system formed about 4.6 billion years ago. It contains a total of 8 celestial bodies orbiting around the Sun that are officially recognized as planets. The four planets closest to the Sun-Mercury, Venus, Earth, and Mars — are called the terrestrial planets because they have solid, rocky surfaces. Two of the outer planets beyond the orbit of Mars — Jupiter, and Saturn — are known as gas giants. The more distant planets, Uranus and Neptune are called ice giants. Let’s take a closer look at each of these celestial bodies starting with the Sun.
The central star of our Solar System is the Sun with a mass of about 1.1x10^30 kg. It is large enough to fit about 1 million Earth inside its massive body and is the closest star to Earth, at an average distance of about 150 million kilometers (or 93 million miles). The Sun is mostly composed of ionized gas with 92.1% hydrogen, 7.8% helium, and 0.1% other elements that are held together by gravitational attraction, producing immense pressure and temperature at its center. It is divided into six regions, the core, the radiative zone, the convective zone, the photosphere, the chromosphere, and the corona. The temperatures at the core of the Sun can reach up to 15 million degrees Celsius (or 27 million degrees Fahrenheit) causing thermonuclear fusion and releasing huge amounts of energy powering the Sun. It takes around 170 000 years for this energy to reach the convective zone from the core due to the energy bouncing around in the radiative zone. Temperatures in the convective zone are about 2 million degrees Celsius (or 3.5 million degrees Fahrenheit) where large bubbles of hot plasma rise upwards. The photosphere or the visible surface of the Sun is a 500-km- thick (or 300-mile-thick) region from where most of the radiation escapes. It takes about 8 minutes for this radiation to reach Earth which we perceive as sunlight. The temperatures at the photosphere can reach about 5500 degrees Celsius (10 000 degrees Fahrenheit) with some areas having strong magnetic fields and being relatively cooler than the rest of the surface. These areas are called sunspots and are mostly darker than the surrounding regions. Above the photosphere are the chromosphere and the corona. These regions are usually outshined by the photosphere making them difficult to see. However, during a total solar eclipse, the chromosphere can be seen as a red rim around the Sun while the corona forms a beautiful white crown with plasma jetting outward. These massive coronal ejections blasting off the Sun are also known as solar flairs with temperatures reaching, quite surprisingly, up to 2 million degrees Celsius (or 3.5 million degrees Fahrenheit). Our Sun is the most important part of our solar system, providing energy and supporting life on Earth. Without the Sun, life as we know it, simply wouldn’t be possible.
