Most heat from the sun arrives as infrared energy. The sun also emits infrared radiation-whose waves are a much lower-frequency. Less potent UV rays travel through the atmosphere, and can cause sunburn. The most harmful UV rays are almost completely absorbed by Earth’s atmosphere. The most high-frequency waves emitted by the sun are gamma rays, X-rays, and ultraviolet radiation (UV rays). The vast majority of electromagnetic waves that come from the sun are invisible to us. In contrast, low-frequency waves have much longer wavelengths. Waves with very short wavelengths repeat themselves several times in a given unit of time, so they are high-frequency. The frequency of a wave represents how many times the wave repeats itself in a certain unit of time.
The electromagnetic spectrum exists as waves of different frequencies and wavelengths. Electromagnetic Radiation The sun’s energy travels to Earth at the speed of light in the form of electromagnetic radiation (EMR). The sun takes about 225 million to 250 million years to orbit one time around the galactic center. Its orbit is between 24,000 and 26,000 light-years away from the galactic center. The sun orbits clockwise around the center of the Milky Way. The sun rotates counterclockwise, and takes between 25 and 35 days to complete a single rotation. The sun rotates around its own axis, just like Earth. Magnetic field lines that flow through the poles extend much farther, thousands of kilometers, before returning to the opposite pole. Near the sun’s equator, magnetic field lines make small loops near the surface. 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. The sun is permeated and somewhat controlled by a magnetic field. 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. Instead, the sun is composed of layers made up almost entirely of hydrogen and helium. It does not have easily identifiable boundaries like rocky planets like Earth. 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. Helium makes up almost the entire remaining quarter.
About three quarters of the sun is hydrogen, which is constantly fusing together and creating helium by a process called nuclear fusion. This means the particles have an increased or reduced number of electrons. 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. 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! Composition The sun is made up of a blazing combination of gases. The sun not only has a much larger radius than Earth-it is also much more massive. That distance is about 109 times the size of Earth’s radius. The radius of the sun, or the distance from the very center to the outer limits, is about 700,000 kilometers (432,000 miles). It takes light on the sun about eight minutes and 19 seconds to reach Earth.
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. This distance, called an astronomical unit (AU), is a standard measure of distance for astronomers and astrophysicists. The sun is about 150 million kilometers (93 million miles) from Earth. 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. Eventually, the gases heated up enough to begin nuclear fusion, and became the sun in our solar system. Much of the hydrogen and helium remained in the center of this hot, rotating mass. As one of these regions collapsed, it also began to rotate and heat up from increasing pressure. The molecular cloud began to compress, and some regions of gas collapsed under their own gravitational pull. A nearby supernova emitted a shockwave, which came in contact with the molecular cloud and energized it. About 4.5 billion years ago, the sun began to take shape from a molecular cloud that was mainly composed of hydrogen and helium. Without the sun’s heat and light, life on Earth would not exist. The sun has extremely important influences on our planet: It drives weather, ocean currents, seasons, and climate, and makes plant life possible through photosynthesis. The sun is an ordinary star, one of about 100 billion in our galaxy, the Milky Way.
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