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What do you know about the Sun?



The surface of the sun.

It's no wonder ancient peoples (and some modern ones) have worshipped the sun. Without its lifegiving warmth, the earth's creatures would die. Our daily moods and activities are also tied to sunshine and the seasons. But how much do we really know about our backyard star? Try this short quiz. Mark TRUE or FALSE by each statement and then turn over the page to see how you did. You may be surprised by the real facts about the sun.

1.___The sun is about 50 times bigger than the earth.

2.___The distance between the sun and the earth is constant.

3.___In the Western Hemisphere, the northern lights are only visible in Canada and the northern United States.

4.___The sun's invisible outer atmosphere is much cooler than its surface.

5.___The surface of the sun is much hotter than a lightning bolt.

6.___The sun is made up of all the same elements that exist in the earth.

7.___Sunspots are cooler than the rest of the solar surface.

8.___The sun's equator rotates faster than its poles.

9.___The sun is about halfway through its predicted life span.


Answers

1. (FALSE) The diameter of the sun is 1,393,000 kilometers (865,000 miles). That's long enough to fit 109 earths straight across the middle of the sun.

2. (FALSE) The sun is actually about 5 million kilometers (3 million miles) closer to the earth in January than it is in July. The average distance from the center of the sun to the center of the earth is 150 million kilometers (93 million miles).

3. (FALSE) The northern lights are sometimes visible in Colorado and have been seen as far south as the Bahamas. Both the northern lights (aurora borealis) and southern lights (aurora australis) are caused by large flares, or eruptions of magnetic energy, on the surface of the sun. Flares and auroras are most common during the peak of the sun's 11-year magnetic cycle.

4 and 5. (both FALSE) The core of the sun is about 15,000,000degrees Celsius (or 27,000,000degrees Fahrenheit). The temperature decreases steadily outward until at the surface it is only about 6,000degreesC (11,000degreesF). In the corona, or outer atmosphere, which is usually invisible and extends millions of miles into space, the atoms become so active that the temperature jumps again to about a million degrees. The center of the earth is estimated to be about the same temperature as the solar surface, while a lightning bolt the width of your thumb is five times hotter.

6. (TRUE) Hydrogen (69.5%) and helium (29%) are the main components of the sun, but all elements known on earth also exist there. Scientists figured this out by looking at the color lines in the solar spectrum.

7. (TRUE) Sunspots are darker and cooler than the rest of the solar surface. Scientists were surprised, however, to find out that the sun gives off the most light when there are the most sunspots. This extra light comes from plages--extremely bright regions surrounding the spots.

8. (TRUE) The equator of the sun rotates once in about 27 days, but the poles take some 9 days longer for each rotation. This is possible because the sun is gaseous, not solid like the earth.

9. (FALSE) Scientists estimate that our sun is about five billion years old and has a life span of another ten billion years or so.


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Edited by Rene Munoz, munoz@ucar.edu

Prepared for the Web by Jacque Marshall
Last revised: Mon Apr 10 14:14:36 MDT 2000