Student Exploration: H-R Diagram
Vocabulary: giant, H-R diagram, luminosity, main sequence, star, supergiant, white dwarf
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
How do the appearances of stars A, B, and C in the photo at left compare?
What are some ways the stars in the photo could be grouped or classified?
In the early 1900s, astronomers were able to identify many star characteristics such as color, size, temperature, and luminosity—or how bright a star is. However, astronomers did not yet understand exactly how these characteristics were related. Using the H-R Diagram Gizmo™, you will discover some of these relationships on your own.
Start by moving your cursor over the stars in the Star collection. Information about each star is displayed on the right side of the Gizmo. The numbers given for Luminosity, Radius, and Mass are in comparison to the Sun. So, a star with a radius of 2 is twice as large as the Sun.
Find Betelgeuse in the Star collection. Fill out the chart at right.
The Sun has a radius of 695,500 km.
What is the radius of Betelgeuse?
Color and temperature
Get the Gizmo ready:
Make sure Arrange stars is selected and Color is selected on the Arranged bymenu.
Question: How is the color of a star related to its temperature
Predict: If you look closely at some stars in the night sky, you can see slight differences in their color. Some stars look reddish. Others appear orange, white, or blue.
What do you think the color of a star indicates about its temperature?
Organize: Compare the colors of the following stars in the Star collection: Aldebaran, Betelgeuse, Sirius B, Spica, the Sun, and Vega. Drag the six stars to position them where you think they would fit on the Gizmo’s color scale.
Click Sort stars on the Gizmo to check your placements. Mark the location of each star on the scale below. Use abbreviations for the star names. For example, “Ald” could represent “Aldebaran” and “Veg” could represent “Vega.”
Organize: On the Arranged by menu, select Temperature. Based on their given temperatures, plot the stars on the Gizmo scale. Mark each star on the scale below. (Note: On the logarithmic scale, the space between 1,000 °C and 2,000 °C is the same size as the space between 10,000 °C and 20,000 °C.)
When you are finished, click Sort stars to check your placements. Revise your chart if necessary.