Final Project: Open Cluster Photometry and HR Diagram Final Report


Goal: The goal in this project is to analyze two different clusters (NGC 7160 and NGC 6940) by creating a color magnitude diagram and find their respective isochrones. We want to do this because we want to categorize the different stellar populations in order to learn more about clusters. All of the data comes from Smith College’s 16-inch telescope and both clusters will be analyzed in the B, V, and R filters.

Technique: To create the color magnitude diagram, we used IDL to reduce and analyze the original dataset. We used the bias’, flats, and darks to fully reduce the data to get the pure picture of the clusters (without noise, internal telescope fluctuations, and hot pixels). We used standard stars (with their darks, flats, and bias’) in order to calculate the zero point, which is subtracted from the magnitudes of the stars. After, we aligned and trimmed the images in order to have the B, V, and R filters the same size and all of the stars aligned. From there, we subtracted the background brightness and created the color magnitude diagram and compared it to known isochrones.

Results: After analyzing the data and finding isochrones, we compared our data to published data from Webda. Both of our clusters are similar to the published data and our isochrones fit our data very well. Also, the ages of isochrones and the metalicity used is very similar to the published data from Webda for both of our clusters. This means that our data is accurate and that our isochrones were a good match.

Part B

The scientific motivation for creating an HR diagram (I will be creating a color magnitude diagram which is a ’flavor’ of the HR diagram) is because the diagram will show the age of the cluster and the distribution of the stellar material. It is important to know the age and metallicity of the cluster because from there, we can understand the evolution of stars and stellar clusters. Astronomers still do not know everything about stars and by analyzing clusters and creating HR diagrams, we can learn more about what is in our Universe and how clusters form, age, and die. Also, because our Sun came from a cluster, we can possibly understand more about individual stars and our Sun from analyzing these color magnitude diagrams. Finally, we can find the distance to these clusters by fitting the isochrone to the color magnitude diagram.