What's This Activity About?: In this activity, students will measure the rotation of a spiral galaxy using the Doppler shift and learn that galaxies are mostly made up of "invisible" mass called dark matter.
What Will Students Do?: Students will measure the mass in dark matter in a nearby spiral galaxy by calculating the speeds at which gas clouds rotate around the center of the galaxy. They will (a) use the Doppler shift equation to convert the observed wavelength of a hydrogen emission line to the line-of-sight velocity, (b) convert line-of-sight velocity to rotation velocity, and (c) use the equation for circular velocity to solve for the 'dynamical' mass of the galaxy. They will then compare the dynamical mass of the galaxy to the mass of the galaxy in stars and gas and learn that 85% of the galaxy's total mass is made of dark matter.
Required: Algebra
Grade Level: Available for both High School students (grades 9 - 12) and College Undergraduates (non-science majors).
Click here for a copy of the high school lab manual.
Click here for a copy of the college level lab manual.
Answers are available upon email request.
If you use this lab project, I'd appreciate hearing about it.
Send me an email at kuzio - at - uci - dot - edu. Thanks! |
|