Sunset

Thanks to the sun, life is possible on earth. The sun provides the major aspect needed for life: Light! The sun is the nearest star. That's why we can study it a lot better than any other star. Since the sun is so clorse, Astronomers learn how stars work by studying the sun. Their studies have provide several interesting results.

Core of the Sun
The core of the sun is extremely hot (approx 15 million degrees Celsius) and there is enormous pressure (100 billion times the pressure you feel on earth). Reaction involves a deuterium. In the nucleus of a deurterium there is one proton and one neutron. Two deuterium fuse to become one nucleus and becomes helium. Every second the sun expends 1400 million tons of deuterium (Hydrogen). Only a small part of it becomes light (0.7%).

Sunspots

Photosphere
The photosphere is that part of the sun which is visible from outside the sun. Every square centimeter of the sun provides as much light as a 6000 Watt lamp. A few years ago there were many sunspots. Sunspots are spots on the sun were the magnetic field is extremely strong. We can see the sunspots as a dark spot, because the magnetic pressure is high and the atmospheric pressuse is low. This means that a sunspot is cooler (4,000 degrees Celsius) compared to the rest of the surface (6,000 degrees Celsius).

Chromosphere

Chromosphere
The chromosphere is positioned just outside the photosphere, and is almost transparant. In the picture you can see the photosphere, as a red glow around the sun. The temperature in the chromosphere increases slowly when you move further outside. It can change from 4,300 - 8,300 degrees Celsius. Outside the corona the temperature decreases rapidly.

Corona

Corona
The corona starts at the top of the chromosphere and it is visible during a solar eclipse. The temperature of the corona is very high: Approximately one million degrees Celcius. That's why it transmits X-rays. The scientists don't know yet why the corona can be that hot. The surface of the sun is only 6,000 degrees Celcius, how can the corona be that much warmer? Outside the corona the temperature decreases rapidly.


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