22.1

Sun

Written by:
Dana Desonie, Ph.D.
Fact-checked by:
The CK-12 Editorial Team
Last Modified: Apr 01, 2026

Lesson

Artist's rendering of the Solar and Heliospheric Observatory spacecraft studying the Sun.

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

Humans have sent spacecraft up to study our star. The Solar and Heliospheric Observatory (SOHO) spacecraft has been in operation since 1995. 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 (Figure below). 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!

Graphic comparing the size of the Sun to a basketball and depicting planets' sizes.
The sizes of the planets relative to the Sun, if the Sun were the size of a basketball.

Summary

  • 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.

Review

  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?

Explore More

Use the resource below to answer the questions that follow.

 

  1. What state is most of the matter in the sun in?
  2. Where is the sun located?
  3. How is energy created within the sun?
  4. How does the sun keep the solar system together?
  5. How does the sun protect our solar system as it travels through space?
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    Image Reference Attributions
    		Credit: Courtesy of NASA
    Source: http://sohowww.nascom.nasa.gov/gallery/Spacecraft/SOHOLower2.html
    License: Public Domain
    		Credit: Courtesy of NASA
    Source: http://sohowww.nascom.nasa.gov/classroom/classroom.html
    License: Public Domain
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