The universe is composed of many many stars.  Our star, the sun, is one of 100 billion stars in our galaxy, the Milky Way.  Our galaxy is just one of billions of galaxies in the universe. This means there are a lot of stars in the universe.  There are stars much larger than our sun and stars much smaller.  What determines the size of a star?  Here is a website about the size and life cycle of stars.  To read about the history of star observation and classification, click here.  How does our sun compare in size with other stars?

This chart shows the sizes of various stars in comparison to our sun, the orange dot near the center of the chart.  The numbers are the cross sectional area of the star in square miles.   To get an idea of big a big star like Arcturus is, remember that our sun has a diameter about 110 times that of earth.  That means that 110 earths could fit across the sun.  Arcturus has a diameter about 600 times that of our sun. 

 
Want to get an idea about our size?  Watch this video

Did you know that stars have different colors?  Well, they do and their color is determined by their temperature.  Their temperature is determined by their size and age.  Our sun is a yellow 'main sequence' star.  Main sequence means that is not new and it is not old.  Its in the middle of its life.  Red stars are cool, yellow ones medium, white stars hot and green and blue stars very hot.

Hubble space telescope image showing stars of various colors.

Interested in more about how star colors and temperatures are related?  Click here 

How are distances in space measured?  Click here to find out.