Exploring the Milky Way using Real Data
Disclaimer: i designed this activity to be used with students who have not yet been taught about galaxies. the idea is that they should be given some data and then see how much they can figure out on their own in a supportive classroom environment. i believe that knowledge which is independently discovered is better understood than knowledge which has simply been memorized. i don’t think this activity is good for students who already know something about galaxies.
Topic/Concept: The Milky Way
Type of Activity: small group + a little discussion at the end
Prerequisite knowledge required: star formation and evolution, gravity, orbits, Newton’s version of Kepler’s third law
Resources required: image packets (see below), worksheets
Learning Objectives: identify the various components of the galaxy, sketch orbits of disk and halo stars, explain where current star formation occurs and compare the ages of disk/halo stars
Common misconceptions:
Detailed description of activity: i put the students in groups of three and give each group a packet of images and each student a worksheet. then i go over each image and explain the galactic coordinate system to them by reminding them of the band across the sky that we saw in the planetarium and called the milky way. i draw some galactic coordinate axes on the board and show how that band gets oriented along the center of the coordinate system and its relative height. i talk about how, in order to do this, we have to project a curved space onto a flat one and remind them that the same thing happens when making maps of the earth. they won’t get much out of the activity if they don’t understand the images so it’s important to take time to go over them well. then i set them free to work on the worksheet in their groups and i leave 10-15 minutes at the end to go over it as a class.
Assessment: this is mostly done through interacting with the students as they work in groups. i suppose you could also collect the worksheet and look over or grade it.
Associated files and images:worksheet (tex), worksheet (pdf), worksheet with answers, page 1 (pdf), worksheet with answers, page 2 (pdf), milky way at different wavelengths (annotated), milky way pulsar distribution, milky way globular cluster distribution, ngc6712 loses stars into the milky way halo, whirlpool galaxy, whirlpool galaxy photoshopped to show more blue in arms, face-on diagram of spiral arms
Comments: this activity has been tried on ~100 astronomy 103 students in discussion sections and worked really well. it was also tried in a condensed form on a class of ~20 grad students from various disciplines and they didn’t like it. my position is that graduate students are not representative of undergraduate students. :) i’d like to have a better plot of the globular cluster distribution.
also, the whirlpool galaxy image shows a lot of red HII regions (h-alpha light) which may confuse the students who think red==cool. the photoshopped version is meant to emphasize the preponderance of blue light in the arms but the red HII regions are still quite visible. you can mention this to the students and remind them about emission lines vs blackbody radiation.
