Composition of the sun

The sun is an ordinary star, one of about 100 billion in our galaxy, the Milky Way. The sun has extremely important influences on our planet: It drives weather, ocean currents, seasons, and climate, and makes plant life possible through photosynthesis. Without the sun’s heat and light, life on Earth would not exist.

About 4.5 billion years ago, the sun began to take shape from a molecular cloud that was mainly composed of hydrogen and helium. A nearby supernova emitted a shockwave, which came in contact with the molecular cloud and energized it. The molecular cloud began to compress, and some regions of gas collapsed under their own gravitational pull. As one of these regions collapsed, it also began to rotate and heat up from increasing pressure. Much of the hydrogen and helium remained in the center of this hot, rotating mass. Eventually, the gases heated up enough to begin nuclear fusion, and became the sun in our solar system.

Other parts of the molecular cloud cooled into a disc around the brand-new sun and became planets, asteroids, comets, and other bodies in our solar system.

The sun is about 150 million kilometers (93 million miles) from Earth. This distance, called an astronomical unit (AU), is a standard measure of distance for astronomers and astrophysicists.

An AU can be measured at light speed, or the time it takes for a photon of light to travel from the sun to Earth. It takes light on the sun about eight minutes and 19 seconds to reach Earth.

The radius of the sun, or the distance from the very center to the outer limits, is about 700,000 kilometers (432,000 miles). That distance is about 109 times the size of Earth’s radius. The sun not only has a much larger radius than Earth—it is also much more massive. The sun’s mass is more than 333,000 times that of Earth, and contains about 99.8 percent of all of the mass in the entire solar system!

The sun is made up of a blazing combination of gases. These gases are actually in the form of plasma. Plasma is a state of matter similar to gas, but with most of the particles ionized. This means the particles have an increased or reduced number of electrons.

About three quarters of the sun is hydrogen, which is constantly fusing together and creating helium by a process called nuclear fusion. Helium makes up almost the entire remaining quarter. A very small percentage (1.69 percent) of the sun’s mass is made up of other gases and metals: iron, nickel, oxygen, silicon, sulfur, magnesium, carbon, neon, calcium, and chromium This 1.69 percent may seem insignificant, but its mass is still 5,628 times the mass of Earth.

The sun is not a solid mass. It does not have easily identifiable boundaries like rocky planets like Earth. Instead, the sun is composed of layers made up almost entirely of hydrogen and helium. These gases carry out different functions in each layer, and the sun’s layers are measured by their percentage of the sun’s total radius.

The sun is permeated and somewhat controlled by a magnetic field. The magnetic field is defined by a combination of three complex mechanisms: a circular electric current that runs through the sun, layers of the sun that rotate at different speeds, and the sun’s ability to conduct electricity.

NGS