Sun+1B


 * __The Sun__**




 * We all know that the Sun is overwhelmingly important to life on Earth, but few of us have been given a good description of our star and its variations. The sun is an average star; it’s similar to millions of others in the universe. If the total output of the Sun were gathered for one second it would provide the U.S. with enough energy, at its current usage rate, for the next 9,000,000 years. The sun’s basic energy source is nuclear fusion. It uses its high temperature to fuse hydrogen, and produces energy and creates helium as a byproduct. Energy that is released from the center of the sun takes about 50,000,000 years to make its way to the surface. Say if the sun stopped producing energy it would take 50,000,000 years for significant effects to be felt at Earth. The sun is 5 billion years old. It has enough hydrogen to continue producing energy for another 100 billion years. The sun will be known as a red giant star when the surface expands, enveloping the inner planets including Earth. This probably would happen in about 10 to 20 billion years. If the sun were more massive it would collapse and re-ignite as a helium-burning star. Because is average size it’s expected to merely contract into a relatively small, a cool star known as a white dwarf.**

__The Core__
===The innermost layer of the sun is called the core. The core is expected to be a solid because it has density of 160 g/cm^3, 10 times that of lead. The temperature of the core is 15 million K or 27 million degrees F. The temperature keeps it in a gaseous state. Fusion reactions produce energy in the form of gamma rays and neutrinos. The gamma rays are absorbed and re-emitted by many atoms on their journey from the envelope to the outside the sun. Gamma ray’s energy is reduced when they leave atoms. The neutrinos are extremely non-reactive. To stop a typical neutrino it would have to go through a light-year of lead.===

__Solar Envelope__

 * The convective envelope surrounds the radioactive envelope, which is the outside of the core. The temperature is 4 million K or 7 million degrees F. The solar envelope has 60% of the sun’s mass in 90% of the volume, while the core has 40% of the mass in 10% of the volume. The solar envelope maintains the core’s temperature. The hotter a gas is the more transparent it is. The solar envelope is more opaque and cooler than the core.**

__Photosphere__

 * The photosphere emits the sunlight that we see. The photosphere surrounds the envelope with a thin layer of low-pressure gasses. The spectrum of sunlight reveals the composition, temperature, and pressure of the photosphere.**

__Chromosphere__

 * The chromosphere is the red circle outside of the sun. It can sometimes be seen in an eclipse. An abundance of hydrogen causes the red coloring. As the distance from the core increases the temperature from the center of the sun to the chromosphere decreases. The temperature is 7000 K.**

__Sunspots__
===__Corona__ The outer layer of the sun is called the corona. You can only see it during eclipses. The corona is hotter than most of the inner layers. It can reach temperatures of 3 million K or 5 million degrees F. The average temperature is 1 million k or 2 million degrees F. Although the corona is very hot it’s a million times less bright than the inner layers.===
 * Sunspots have the same diameter as the Earth. Sunspots are just dark spots on the photosphere. The center of the spot is called the umbra it looks dark gray. The penumbra, which looks light gray, is around the umbra. It takes a sunspot 11 years to increase sharply and decrease sharply. The sunspots are produced by magnetic fields that reach from pole to pole. The loops in the magnetic field oppose convection and it stops the flow of energy to the surface. This makes cool spots, which produce less light in the warmer areas.**