CM4Seyferts SDSS Globular Cluster CM Exercise
[[Media:]]== An Exercise in Globular Cluster Distance Measurement ==
Attached here is an Excel file with data from two clusters. This is not what I give the kids. I give them LESS data than what is here. I make them take the raw data and knowledge of the distance to NGC 6791 to calculate the stars' absolute values for that cluster. That then becomes the "standard HR Diagram" for stars which they can use to compare to the more distance PAL5 (Palomar 5) cluster for which only apparent magnitude information is given. All this data was pulled from the SDSS using their radial search tools. In this particular file, there is a plot with NGC6791 already on it using its absolute G magnitude. Also plotted is the raw PAL5 apparent G magnitude....and a shifted PAL5. There is a cell labelled "SHIFT" which is the delta-magnitude used for the relationship: m-M = shift = -5+5LOG(D). By entering a shift value, the PAL5 cluster plot is moved up or down relative to the known NGC6791 data. A box labeled "Distance" is then automatically updated to show the distance to PAL5 in parsecs. If anything this is a great way to learn Excel.... and a good way to get into discussions about distance measurements using the HR Diagram, CM diagrams as a whole, and even interstellar reddening if you want. Enjoy!
Theresa here: I simply asked my students to to the activity described the link John sent: http://skyserver.sdss3.org/public/en/proj/advanced/hr/globularcluster.asp
The kids selected the stars, downloaded the data and made graphs with excel. They then copied and pasted their graphs to a google doc and shared them with me.
This is what I got:
Media:GlobularClusterHRDiagrams.docx
Tom here: Here are my H-R Diagrams as displayed in "Logger Pro." I have pasted them into a WORD document. Its easy to see the turn-off for Palomar 5, by the one for Palomar 3 is not nearly as pronounced.
Media:Palomar 5 and Palomar 3.docx
Here are the graphs of one of my students, both Palomar 3 and Palomar 5
Media Palomar 5.xlsx
Media Palomar 3.xlsx
Nicole here: These are my H-R Diagrams.
Media:Granucci Palomar HR Diagram 2013.xlsx
