Accessing Prior Knowledge

The Sun

High School


Students will consider the question “Do stars change over time or stay the same forever?” and justify your answer. They will anonymously add their answer to the collection for a group discussion.


  • Slideshow page with a picture of the Sun and the question
  • A small sheet of paper for each student (half sheets would work well)


Have the slideshow displayed for the class when they arrive. Hand each student a half sheet of paper. Ask them to write their response to the questions and crumple up their paper. In the front of the classroom, have an empty box where students will shoot their ‘basketballs’. Alternatively, just have all students throw their papers at the whiteboard at the front of the room. Whatever works for your classroom is fine. Each student will retrieve a paper and read out an answer. The teacher or a designated student will tally the responses on the board and record the reasons for each. Once the results are recorded, students will make a record on their Student Handout.


Student knowledge may be limited to the fact that the Sun is a part of the solar system and Milky Way galaxy and that there are many other galaxies out there. They may not realize that the Sun or other stars have a life cycle. While students are working to answer the questions, walk around the room and probe them based on what they know about the Sun.

  • Where did the Sun come from?
  • What is the Sun made of?
  • How does the Sun use hydrogen?
  • What happens to the energy from the Sun?

Accessing Prior Knowledge activities help the teacher identify possible student misconceptions. The following misconceptions are addressed by this activity:

  • Students may assume stars do not change.(All stars follow a life cycle and evolve from life to death.)
  • Students may think more massive stars last longer than less massive stars. (The core of a massive star is hotter and denser so it burns much faster and has a shorter life than smaller stars.)
  • Students may think that the stages in the life cycle of a star are equal time periods. (A star will spend about 90% of its life in the main sequence phase, in which hydrogen nuclei fuse to helium nuclei in the core.)
  • Students may assume a red giant star is the last stage of a medium star. (All red giants are variable stars. Their core keeps on contracting and heating up until it is hot enough for the triple-alpha process (also known as helium flash) to take place. In this reaction, three helium nuclei will fuse together to form a carbon nucleus. Since the hydrogen-burning shell and helium-burning core do not produce energy in a stable and steady manner, the star will pulsate and generate strong stellar wind. Eventually, the entire outer shell will be ejected. The gas ejected will form a thin shell around the star. It is a planetary nebula.)
  • Students may assume the Sun will live forever. (The Sun is only 4.6 billion years old and it has about 5 billion more years as a main sequence star before it begins to change into a red giant, form a planetary nebula, and eventually burn out.)
  • Students may assume that many of the visible stars in the night sky are far beyond our Milky Way Galaxy. (All of the visible stars in the night sky are part of our Milky Way Galaxy, with the thickest part appearing to arc across the sky. The exception is a fuzzy blur known as the Andromeda Galaxy, which is 2 million light years beyond our own galaxy.)




Student Handout