The Sun is our nearest star!

It took thousands of years for us to realize this simple fact, but now we can use it to our advantage as we study other stars in the universe. Nothing beats having a close-up example of something to study, that otherwise looks only like a spot of light in the night sky! We have a ring-side seat in our own solar system to explore one of the most fascinating kinds of objects in our universe.

If you have any questions about the Sun, visit Ask the Space Scientist!

Basics: The Sun is actually an average-sized star that formed, along with the rest of the solar system, about 4.5 billion years ago. The Sun is located 93 million miles (150 million kilometers) from Earth. Sun gives us light and heat to warm our planet Earth. It is a huge ball of gas 100 times bigger than Earth, and composed of 74% hydrogen and 23% helium. All the rest of the elements we know here on Earth make up only 3% of the mass of the Sun, and most of this is in the elements carbon, nitrogen and oxygen. The Sun produces nearly 400 trillion trillion watts of energy in the form of light. A small part of this falls upon Earth and makes our planet habitable. The temperature at the surface is nearly 6,000 degrees Centigrade. The gases move at thousands of miles an hour. You can't stand on the surface of the Sun even if you could protect yourself. The Sun is a huge ball of heated gas with no solid surface. The Sun's surface is always moving. Sometimes storms bigger than the size of Earth can send gas and energy flowing into space.

  Watch a Prominence Movie

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The Surface: On the surface of the Sun, gases move in a rolling motion called convection. These convection cells can be seen as solar granules that are several thousand miles across, and change shape within a few minutes. You can see the same kind of motion by looking at the water in a boiling pot of water. This convection motion produces many phenomena on the surface, because as the gases flow, they produce electrical currents that generate powerful magnetic fields. Intense concentrations of magnetic energy cause sunspots to form - dark spots on the solar surface that are many times larger than Earth. They appear dark because they are several thousand degrees cooler that the rest of the surface. Solar flares are explosive releases of magnetic energy near sunspots which flash powerful blasts of X-rays deep into the solar system. These X-rays can be harmful, or lethal, to unprotected astronauts working in space. They can also cause radio blackouts over the entire day-side of Earth lasting several hours. Prominences are giant loops of magnetism that trap heated gas, making them glow. Scientists can study these gasses to see how the magnetic lines of force are oriented in space, the same way you use iron filings to study the magnetic field of a toy magnet in class. Prominences are like pencils balanced on their point. They can appear motionless for hours, then suddenly erupt, spewing out their trapped gases into space. As you ride the solar convection you find yourself swimming around with sunspots and other odd things. Suddenly, like some enormous earthquake, the gases around you start to move violently. Everything around you begins to move away from the Sun in a huge cloud of hot gas!

 Watch a Solar Surface Movie

 Look at an Enlarged Picture

Storms: You are part of a huge cloud of gas that starts out over 10 times bigger than the entire Earth. It grows bigger and bigger as it moves away from the Sun. The bubble will travel through space at nearly a million miles an hour. Scientists call this a Coronal Mass Ejection or just 'CME' for short! If your car could travel as fast as a CME, you could take a cross-country trip from New York to San Francisco in about 15 seconds! The cloud you are riding is shaped like a gigantic gas bubble that is hollow inside. We are lucky, here on Earth, that very few of these gigantic storm clouds are shot towards the Earth. As spectacular as CMEs seem to be when seen near the Sun, by the time they reach Earth and beyond, they have dropped to incredibly low densities of only a few dozen atoms per cubic inch. The blend into when astronomers call the interplanetary medium - a low-density gas flowing out from the Sun at about 400 kilometers per second. This 'solar wind' flows past the planets and leaves the solar system entirely in its journey to the stars. The solar wind is actually the outermost layers of the Sun being evaporated into space, so this means that all of the planets in the solar system are actually orbiting inside the atmosphere of the Sun! We hardly know it's there because this solar wind is deflected by the magnetic fields of most of the planets, and even without such a protecting field, Earth would only accumulate a few hundred tons of gas per year from this wind.

 Watch a CME Movie

 Look at an Enlarged Picture

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