4.1a The sun

How can we learn about something as hot as the sun?

Humans have sent spacecraft up to study our star. The SOHO spacecraft has been in operation since 1996. The craft orbits the Sun in step with Earth but closer to it. SOHO has sent back amazing images. Onboard instruments have also sent back mountains of data. The data is mostly about the sun’s outer layers.


The Sun

Our sun is a star , a sphere of plasma held together by gravity. It is an ordinary star that is extraordinarily important. The sun provides light and heat to our planet. This star supports almost all life on Earth.

The sun is the center of the solar system , which includes all of the planets and other bodies that orbit it. It is by far the largest part of the solar system ( Figurebelow ). Added together, all of the planets make up just 0.2 percent of the solar system’s mass. The sun makes up the remaining 99.8 percent of all the mass in the solar system!

The sizes of the planets relative to the sun, if the sun was the size of a basketball.


  • solar system : The Sun and all of the bodies that orbit it.
  • star : A massive sphere of plasma held together by gravity


  • The sun is an ordinary star. It supports nearly all life on Earth.
  • The sun is at the center of the solar system.
  • The sun makes up almost all of the mass of the solar system.


Use the resource below to answer the questions that follow.

  • The Sun Encyclopedia of Secrets at
  1. What is the sun?
  2. How far is Earth from the sun?
  3. What is found in the sun?
  4. What type of star is it?
  5. Explain early beliefs about the sun’s production of energy.
  6. What fuels the sun?
  7. How hot is the core?
  8. What is formed from nuclear fusion?
  9. What are photons?


  1. What are the major properties of the sun?
  2. Where is the sun located?
  3. Why is the Sun important to life on Earth?

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