Brief(15 minute) Activity for redshift of galaxies using the Sloan Digital Sky Survey Site

We are going to look at some galaxies from the Sloan Digital Sky Survey. As the galaxies get further away, what changes should we notice? (Have student’s list ways on a piece of paper. Make a master list from their suggestions.)

Look at the site: http://www.sdss.org/gallery/ (the bottom of the page, select galaxies) or

http://www.sdss.org/gallery/gal_zgalaxy.html

The rows of galaxies that are further down the page are further away. Students should list the things they notice about the galaxies. They should see:

a.       Dimmer

b.       Smaller

c.       Redder

d.       Change of shape

Next students will check out the spectra of quasars as they get further and further away. It’s best for students to be familiar with spectra of elements, especially hydrogen. Take a look at the spectra of the quasars or so (quasi-stellar objects).

A good website for spectra:

http://www.phys.ksu.edu/perg/vqm/tutorials/hydrogen/

This is a great page for looking at different spectra.  The webpage uses shockwave and a virtual spectra tube lamp.

http://phys.educ.ksu.edu/vqm/html/emission.html

Site: http://www.sdss.org/gallery/gal_zqso.html

Students should shift the window over so they can see as much of the spectra window as possible. They should choose one emission line and follow it as they scroll down the page fairly quickly (scroll down the whole page in less than thirty seconds.) Make sure students know the quasars are getting further away as they go down the pageant the red end of the spectra is on the right and the blue end is on the left. They should notice that the same line move toward the red side of the spectra.

This brief exercise should familiarize the students with the basics of redshift of galaxies.