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.
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.
Grade Level:   Roughly 3rd grade level.
The crossword puzzle can be found here.
Answers are available here.