Name: _______________________________
Date: _____________
Class Period: _______
Chapter 18 Virtual Lab: How does the Chemical Composition of Stars affect their Classification?
You may access this lab via my website. Due Date: ________________________________
Background Information: Scientists Ejnar Hertzsprung and Henry Russell were astronomers in the early 1900’s. Their
research led them to determine there was a pattern to the relationship among the color, temperature, and brightness of
stars. Their H-R diagram shows how stars fall into categories, with most stars falling into a diagonal band at the center,
called the Main Sequence. About 90% of all stars fall into this category.
In addition, the H-R diagram also shows absolute brightness. Absolute brightness is one way to measure the actual
amount of light given off by a star. By looking at the spectrum of light that the star produces, we can also determine if a
star contains a particular element.
Objective: Compare the spectra of light produced by unknown stars to determine the chemical composition of stars.
Determine the placement of unknown stars in the H-R diagram based on analysis of its spectra.
Task 1: Complete the table below by clicking on “Spectral Classes”.
Star Type
Temperature
Range
Prominent Spectral Features
O
B
A
F
G
K
M
Task 21. Choose a star by clicking the arrow under star and selecting a letter. You will see the spectrum for that star.
2. Determine what elements are present in the star. Select an element by clicking the arrow under element. You
will see a spectrum for that element. Record your data below in the data table.
3. Record the star’s brightness and relative temperature in the data table.
4. Click on the “Spectral Class” button. Determine the star’s place in the H-R diagram. Record the star’s spectral
class letter in the data table. Place the star in the H-R diagram and click “Check”.
5. Record the star color in the data table.
6. Place all the stars in the diagram and complete the data table.
7. ***IMPORTANT**** You will need to print your H-R diagram. To do this, right click on the page. A menu will
pop up with “PRINT” as an option. Print a copy of your H-R diagram. You will hand it in with your lab and it
will count for points.
Star
Elements
Present
Brightness
Temperature
(K)
Spectral Class
Letter
Star Color
A
B
C
D
E
Task 3- Complete the questions below.
1. What is known about the temperature of stars placed on the left side of the H-R diagram?
______________________________________________________________________________________
2. What is known about the brightness of stars placed near the top of the H-R diagram?
______________________________________________________________________________________
3. What is the main chemical composition of stars that are very hot and very bright?
______________________________________________________________________________________
4. Where would you find a cool, dim star on an H-R diagram? Mark it with an “X” on your H-R diagram.
5. Where would you find a hot, bright star on an H-R diagram? Mark it with a “+” on your H-R diagram.
Website: http://www.glencoe.com/sites/common_assets/science/virtual_labs/ES24/ES24.html