Star Classification and the H-R Diagram

Kasey Poorman

Melissa Lanyi


Grade level: †† 8th grade

Topic:††††††††††† Classification of Stars


National Science Education Standard and Pennsylvania standard:


This topic follows the Pennsylvania Science standard 3.4.10 D.This standard is to explain essential ideas about the composition and structure of the universe.More specifically, this lesson is focused on describing the structure and life cycle of star, using the Hertzsprung-Russell diagram.

The National Science Education Standard is content standard B for physical science which states that as a result of their activities in grades 5-8, all students should develop an understanding of properties and changes of properties in matter, motions and forces, and transfer of energy.

Instructional Objectives:

As a result of this lesson, students should be able to understand how the Hertzsprung-Russel (H-R) Diagram is used to classify stars according to their luminosity and temperature.They will be able to recognize different classes of stars according to spectral types, for example: OBAFGKM.Students should realize that the sun is only one type of star, and its type is not even the most abundant. Students will question whether the other types of stars could be suitable for supporting life in a solar system.

Content Explanation:

The big idea of this lesson is for the students to be able to realize that stars come in many colors, and why. They will learn how to classify a star by its properties and that a starís color is determined by its temperature. From the information they learn about stars and their properties they will learn that hot stars generally have a shorter lifespan than cool stars. The sun is a yellow star, which is in the middle of the color and brightness spectrum, but yellow stars are not the most prevalent type in the universe.


Administrative Considerations:


Students will work together as a group or individually if they wish.They will stay seated during the lesson and will not be working with any materials that they may need to take precautions with other than paper and a writing utensil. This lesson is directed towards aspects of astronomy which is a topic that is directed toward people from different backgrounds.

Materials, equipment, and set-up:

The materials that will be needed for this lesson will be pencils and the provided worksheet for each student.The instructors will have a large poster board with an H-R diagram to present to the students.They will also have removable stars according to their different classifications to place on and off of the diagram.

Body of the Lesson:

Engagement: (2-3 minutes)

Questions will be asked to engage the students such as:

Is the sun a Star? A big star or small star?

What color is the sun?

Do you think all the stars are the same? Same temp? Same color? Same apparent Brightness?

Exploration: (5 minutes)

Our guiding question is to let the students explore to see if there is a difference in different-colored stars and the relationship between color and temperature, mass, and age.We will discuss with the students different properties of stars and how they are placed on the H-R diagram according to temperature and luminosity.We will make sure the students understand the concept of luminosity and how it relates to the stars temperature and how temperature relates to colors of stars.We will do this by using a large H-R diagram and allowing students to make predictions about where they believe stars go on the diagram and how to analyze the trends of a completed diagram.


Explanation: (5 minutes)


We will help the students understand the diagram by explaining different types of star groups and where they fit into the main sequence of the H-R diagram.We will discuss main properties of the different groups and what their luminosity and temperature will most likely be.


Evaluation: (5 minutes)


The students will be given a worksheet on which they will be asked to classify stars into their designated spectral groups using some given information on another worksheet about the stars properties.Once they have done this we will go over it as a group to make sure they fully understand what they learned from this lesson.


Time permitting, when the students finish their worksheets and we have gone over it, we willhave the students plot the stars that they have classified on the large diagram that was used by the instructors.


Clinic 2 involved teaching a lesson at Park Forest Middle School to three groups of about 3-4 students each. The topic that my partner and I decided upon was star classification using the H-R Diagram. Overall, I think that the lessons went very well and the students seemed to be very interested in this topic.

††††††††††† The classroom was set up very conveniently for us to teach because each group had their own lab table in which the teachers stood behind and the three to four students were facing us in stools. I think that my partner and I were nervous in the beginning because we were not sure how much the students would be interested in our topic. Once we got through the first session and saw that the students were very interested and involved in the lesson, we were much calmer and confidant for the next two sessions. The pace of the lesson was pretty smooth after we got to understand what the studentís prior knowledge about the material was.

††††††††††† I think that the hardest part of the lesson was starting out because we were not sure how much prior education that the students had about the topic of star classification and we didnít know if they had ever even heard of the H-R diagram. We prepared a pre instructional diagnosis of studentsí conceptions which included a broad range of questions to ask them because we were not sure how much they already knew. The students ended up knowing that the sun was a star and that they are different color stars based on their temperature but they did not know anything about the H-R diagram which was ok because that was what we had expected.

††††††††††† After we asked the students questions about the concept of star classification and determined what they knew and didnít know, we introduced to them the H-R Diagram. I discussed with them how the x-axis represents temperature and the y-axis represents luminosity and then I showed them the different groups of stars that are found in each section of the H-R diagram. They were asked to point out trends in the different groups of stars such as the main sequence star, the red giants, blue giants, and dwarfs. They were told to tell us what characteristics each group possessed such as their size, temperature, luminosity, according to the diagram. The students were then given post-it note stars with the temperature and luminosity written on them and they were asked to plot those stars in their correct positions on the diagram. They also did a supplemental worksheet to go along with the lesson that asked them to determine the color and classification group of a list of stars based on the temperature and luminosity of the stars.

††††††††††† The worksheet that we had the students complete was our assessment of what they had learned from the instruction that we had taught them earlier in the lesson about the H-R diagram. The other assessment that we planned was when they were to place the stars in the correct positions on the H-R diagram. If a student had an error in their work or placed the star in the wrong position then we investigated the problem to determine what their misconception might have been.

††††††††††† There were a few unexpected errors that arose throughout the process of the three lessons. One of the stars that we had labeled had a luminosity listed on it that was beyond the scale of the H-R diagram and did not fit on the board. This error could have been avoided by checking all of the stars luminosities and temperatures beforehand to make sure that they were all correct and fit onto the board. The other error occurred in the last session that we taught; we had about five more extra minutes at the end of the lesson than we did in the other two sections. We had already plotted the extra stars on the diagram which was our original back up plan for extra time at the end, so we were not sure what to do with the students in this time. We ended up just talking to the students about prior topics that they had learned in science class which turned out to be ok.

††††††††††† I wouldnít make any major changes to the lesson because I thought that it went pretty well but I would make some slight adjustments. I think that I would plan better for any extra time left in the end after the completion of the lesson is over just to make sure that they have enough to do.