The Sun: Our Home Star
The star we call the "sun" is a huge sphere, positioned roughly at the center of our solar system. The sun emits energy that powers processes on every planet in the solar system, and is the source of almost all energy on Earth. (For a look at how the sun's light is used to power processes on Earth, visit the Earth's Energy Budget page.)
The Sun's Motions:
Important Facts about the Sun:
Relative Temperatures of the Sun's Regions:
Structure of the Sun:
1. The sun's surface is made up of superheated matter called "plasma".
2. The great mass of the Sun causes gravity at its surface to be 28 times as strong as the pull of gravity on the surface of Earth!
3. The sun's surface is not "flat" but is covered in small individual areas or bubbles we call "granules". These individual granules are about the size of a city may last only a few minutes.
4. Sunspots are darker blemishes on the surface of the Sun. They usually appear in pairs. Sunspots seem to be closely related to extreme solar weather such as solar flares and coronal mass ejections (CMEs).
5. Sunspots provided evidence that the Sun rotates on its axis, tilted at 7 degrees. This was observed by Galileo Galilei (1610), Johannes Fabricius and Thomas Harriott.
6. Sunspots have two parts: A dark center (umbra) and a lighter outer portion (penumbra).
7. Sunspots appear in cycles that seem to be 11 years long. Some years we may have hundreds of sunspots, and some others we may have very few. No one is yet 100% sure why...
8. Solar flares (see pg. 68 of your book) and Coronal Mass Ejections are violent storms and eruptions from the Sun's surface that can affect Earth and its inhabitants. Much research is being done to help up understand Solar Weather.