Open clusters in the Milky Way galaxy:

M16, the Eagle Nebula

Sprinkled along the Milky Way, star clusters present a snapshot of star formation and evolution. But the first step in any study is to determine their distance. The background document, links to the necessary software, and data for such a study can be found below.

Students may benefit by first exploring a simpler cluster project, Jewels of the Night, or by visiting the Sloan site for background on stars and the H-R diagram.

The Jewels of the Night is an activity for middle school and up. No computer access is required. Students measure the color and brightness of stars in the Jewelbox Cluster from a color image. They determine the age of the cluster by plotting their measurements in a color-brightness diagram. Students are exposed to ideas about the nature of stars, temperature and color, stellar evolution, the time scales of astronomical phenomena, and how astronomers can determine the ages of objects in the universe. The student instructions, student answer sheet, and graph worksheet can be printed directly from these Web pages in black and white, and reproduced for classroom use.

Sloan Digital Sky Server (HR diagram project) : an on-line project developed here (follow projects > basic> color) presents all the steps in determining the properties of stars.

Open Clusters research project using NOAO Data
In this research project you will have the opportunity to examine data for a variety of clusters. Many of these clusters have not been studied in years: their distance may have been determined with photographic plates as long ago as 1930. As with any area in science, the chance to make a better measurement is never to be passed up! You will make measurements using ImageJ and an available plugin of the intensity (or magnitude) of numerous stars in the CCD images taken with the 0.9M telescope. You will grapple with the question of which stars in the image are cluster members and which are just foreground or background stars. And finally you will compare your results with a known calibration to determine the distance to the cluster.

Download the background document: Open_cluster_intro.pdf [492 KB pdf]

The software necessary for handling the data is the program ImageJ which is available as a free download from the ImageJ web site. To get the program itself, click on “Downloads,” and choose the version of ImageJ appropriate for your computer. Unzip and install on your computer.

You will also need an astronomy plugin for ImageJ which you can download here. This will permit you to measure intensities as outlined in the background document.

The background document discusses data for the cluster M26:

Additional data for other clusters:

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The Astronomy RBSE program is administered by the National Optical Astronomy Observatory with funds from the National Science Foundation.