The Sun

[Layers | Sunspots | Solar flare | Solar prominence | Images]

The sun is the closest star to earth. It is a giant ball of gas with no solid surface. The surface of the sun is effected by changes that go on inside the star. The three main parts of the sun are: the photosphere, the chromosphere, and the corona.
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Layers

[Photosphere | Chromosphere | Corona]

The photosphere is the visible surface of the sun. It is not solid, but made up of hot glowing gasses about 500km deep. Its temperature reaches approximately 6000K (Kelvin). The sun has a series of convection currents. Hotter matter from within rises to the surface, cools, and recedes back to the center.
The chromosphere lies above the photosphere and is a layer of gas approximately 10000km deep, and about 1000 times less bright than the photosphere. This is the part of the sun that is seen during a solar eclipse. The chromosphere contains flame like structures called spicules, which last for 5 to 15 minutes. These appear to be cool regions extending up into the corona.
The corona is the sun's atmosphere above the chromosphere. It extends as far as twelve solar radii from the surface of the sun. It has a temperature of about 500,000 and 2,000,000 K. The density of the corona must be small for the atoms to attain such temperatures and not emit a great deal of radiation. In the outermost layer of the corona, particles have such great amounts of kinetic energy, that the gravitational pull of the sun can not hold them in. These particles fly outward creating the solar wind. It contains mostly protons and electrons. Particles that are caught in the magnetic field of the Earth create such sights at the auroras near the poles.
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Sunspots

Sunspots are regions of intense magnetic activity on the surface of the sun. Sunspots glow very bright, but compared to the photosphere, are cooler by 1000 K and relatively dark. Sunspots appear in pairs, one the positive terminal, the other the negative terminal. Galileo, who saw the sunspots traversing the surface, found the first evidence that the sun rotated on its axis every 25 days. Sunspot activity peaks and ebbs on an eleven-year cycle. The eleven-year cycle is explained as a result of the sun exhibiting differential rotation. the equator rotates faster than the North and South Poles. Thus, the magnetic fields get tangled. When the fields burst through the surface, they form sunspot pairs. Every eleven years the sunspots reverse the direction of the magnetic points. This theory is called the Babcock model.
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Solar Flare

A solar flare is a violent eruption on the surface of the sun. Some flares release as much energy as one billion atomic bombs and can reach many times the Earth's radii into the solar system. Just like sunspots, their appearance is effected by the magnetic fields of the sun.
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Solar Prominence

A solar prominence is a large arch-like or eruptive stream of gas. They are much larger than sun flares.
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Images

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