Some Facts about the Sun
The Sun is a star.  You may have read that it is a typical star.  Not so!  The Sun is actually a rather rare star, as stars go.  It radiates more energy (light and heat) than 99% of the stars in space!  This may be hard to believe because most of the stars you can actually see in the sky at night are indeed far more luminous than the Sun.  It's just that most stars are much fainter than the Sun and can't be seen without a large telescope.  

What is a star?  Well, most stars are huge balls of hot luminous gas held together by gravity.  They are gas throughout.  There is nothing solid in the Sun. 
 
 

Our star, the Sun, is huge.  Its diameter is about 100 times the diameter of the Earth.   

Even though the Sun is gas throughout, photographs of the Sun seem to show a surface.  This apparent bright surface is called the photosphere.  It's the place where the light from the Sun appears to originate. 
 
What is the photosphere?  There is no "real" surface on the Sun such as the surface of the Earth.  What looks like the surface is in reality a boundary between where the gas is transparent and where it becomes very hazy!  It's so hazy you can't see deeper into the gas.  This boundary is the photosphere.  The temperature of the gas at the photosphere is about 10,000° Fahrenheit.  The gas is almost all hydrogen gas. 

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