Andromeda's Scale

An activity about angular, (apparent) size and magnification in astronomy


Student Worksheet | Teacher's Page

False color image of Andromeda in the optical
Students do a classroom activity of measuring the angular size of something from several distances.  On the Internet, they obtain and examine images with various magnification factors and estimate the angular size of Andromeda. 

Key Question:
What is the meaning of angular or apparent size, and what does it tell us about an object?

Learning Objectives: 
Students understand that angular size is useful for comparing images of different objects, but that it does not give information about physical size unless the distance to the object is known.

Best for Grades:  9 - 12

Nation Science Education Standards:  Earth Sciences 9-12 E, G

Student Prerequisites:
Ability to measure distances,  understanding of ratios and proportion, ability to use a Web browser.

Materials Required:
Measuring tapes or string and rulers for measuring distance, Internet connected computers with basic Web browser installed.

Time  Required: 1/2 to 1 50-minute period