GRADE LEVEL: 

7 - 12

OVERVIEW: 

Completing a short estimation activity the students will gain a better understanding of what a variable star is and how it can be measured.

PURPOSE: 

Through the activity the students will understand why variable stars are important to study and how the research is conducted using interpolation.

OBJECTIVE:

  The Student will:

• Define interpolation.
• Estimate the magnitude of a star in a star field.
• Discuss why study variable stars.

CURRICULUM STANDARDS: 

SI-M-A3, SI-MB4, SI-H-A3, SI-H-B3,
ESS-M-C1, ESS-M-C2, ESS-M-C8,
ESS-H-D3

MATERIALS: 

Estimating Variable Stars using Interpolation worksheet, calculators for averaging, overhead of variable star taken at different times.

BACKGROUND INFORMATION:

Variable stars are stars that change in brightness. These visible changes in brightness help us understand the nature and evolution of stars and galaxies. To discover variable stars you would use two or more comparison stars with known magnitude. These stars do not change in brightness and knowing these magnitudes give you a range to compare to the variable star. When we estimate the magnitude of variable stars the process we use in interpolation. Interpolation is the process of estimating a value between two known values. Have Students write this definition on their worksheet.

PROCEDURE: Activity A

1. Discuss the background information with the class.
2. Hand out the Estimating Variable Stars using Interpolation worksheet, one for each student.
3. Students should estimate each star on their own.
4. Groups should compare estimations and record average for the group.
5. For class discussion record group’s averages and find the class average, record.

DISCUSSION INFORMATION:

The stars in each star field A, B, and C are all the same stars taken at different times. Notice the various magnitude of each. One star does not have the same magnitude label because its magnitude changes in each box. This is a variable star; it varies in its magnitude. These visible changes in brightness help us understand the nature and evolution of stars and galaxies. Observations of variable stars are plotted on a graph called a light curve as the apparent brightness (magnitude) versus time. Several years' of observational data can reveal the changing period of a star. Light curves show that variable stars exhibit simple periodic behavior, they repeat in a regular way that is predictable. There are Intrinsic Variables, where changing brightness is due to some internal cause and Extrinsic Variables, where variability is due to the eclipse of one star by another or the effect of stellar rotation.

1. Pulsating variables are stars that periodically expand and contract (intrinsic).
2. Eruptive variables consist of stars that brighten or dim suddenly and, usually, unpredictably (intrinsic).
3. Eclipsing Binary Stars are found in binary systems in which one star periodically passes in front of another as seen by a remote observer (extrinsic).
4. Rotating Stars variability is due to the effect of stellar rotation (extrinsic).
   

PROCEDURE: Activity B 

Use the Highland Road Park Observatory to view variable stars at different times. You will have to submit an application to use the HRPO Telescope (link to form). Find variable stars and coordinates before hand using Starry Night Pro. 

On tool bar go to Sky - Mark Variables - then select a star - right click - information window- for more information click on Starrynight.com. You may be able to see some variable stars change in a short time. 

INTERNET RESOURCES:

http://hoa.aavso.org/preface.htm
Information on variable stars. Discusses the American Association of Variable Star Observers (AAVSO).