The Sun is the closest star to Earth and is the center of our solar system. It was born in a vast cloud of gas and dust around 5 billion years ago and is a huge ball of incandescent plasma. The Sun accounts for more than 99.86% of the mass of the Solar System. It provides all the energy we need for life here on Earth. It’s light heats our planet and makes life possible.
The Sun sends light and heat rays (called infrared, IR) and some ultraviolet light (UV). The UV is dangerous to living organisms; it damages eyes, human skin and tree leaves, among other things. Fortunately only a few percent of the energy arrives as UV, the rest is halfvisible light, half (invisible) IR.
The Sun produces its energy through what is called the Proton-Proton Chain, which is the act of nuclear fusion . The energy released is E = mc2. The Sun converts 600 million metric tons of hydrogen to helium every second and maintains its steady burning cycle by a process called hydrostatic equilibrium. This means the force of the energy exerted by the core of the Sun is equal to the amount of gravity collapsing toward the core.
The Sun is made up of about 2 x 1030 kilograms of gas. It is composed of about 75% hydrogen and 25% helium. About 0.1% is metals (made from hydrogen via nuclear fusion). The Sun’s core can reach 10 to 22.5 million°F. The surface temperature is approximately 9,900°F (5,500°C). The outer atmosphere of the Sun is approximately 1.5 to 2 million degrees.
Our Sun is one of at least four hundred billion stars in the Milky Way galaxy, and it lives 2.5 billion miles from the center of the galaxy. All stars in our galaxy and other galaxies come in different sizes and colors, and our sun is a medium sized star known as a yellow dwarf.
- When all the Hydrogen has been burned, the Sun will continue for about 130 million more years, burning Helium, during which time it will expand to the point that it will engulf Mercury, Venus and the Earth
- The Sun generates solar wind
- Because of the Sun’s huge influence on Earth, many early cultures saw the Sun as a deity or god. For example, Ancient Egyptians had a sun god called Ra while in Aztec mythology there is a sun god named Tonatiuh
- One million Earths could fit inside the Sun
- Light from the Sun takes eight minutes to reach Earth
- The mass of the Sun is approximately 330,000 times greater than that of Earth
- A solar eclipse occurs when the Moon is between the Sun and the Earth
- The Sun travels at 220 kilometres per second
- The Sun is so hot that molecules are torn apart into atoms, which are, in turn, mostly torn apart into a plasma of charged particles: positive ionized atoms (including “bare” nuclei) and negative electrons
- Because the Earth travels on an elliptical orbit around the Sun, the distance between Earth and the Sun varies from 147 to 152 million kilometres. The distance between the Earth and the Sun is called an Astronomical Unit (AU)