De-Coding Starlight: From Pixels to Images - Middle School

Materials

1. Student Handout Sheet
2. Calculator
3. Colored Pencils (with at least five different colors for each student group)

Objectives

1. The student will use data collected from the Chandra X-ray Observatory to calculate the average pixel intensity of X-ray emissions from a supernova remnant. (A pixel is any of the small discrete grid squares that together constitute an image).

2. The student will interpret a "false color" image formed from real data.

3. The student will develop explanations as to why scientists employ computers to process and analyze astronomical data.

Preparation

1. Before conducting this activity, the students should be introduced to and understand the mission and operation of the Chandra X-ray Observatory. Significant introductory resources are available at the Chandra web site (http://chandra.harvard.edu). Specifically, the following areas of the web site concern the objectives of this activity.

   1. The Chandra Mission http://chandra.harvard.edu/about/axaf_mission.html

   2. Data Collection Instruments on Chandra http://chandra.harvard.edu/about/science_instruments.html

   3. Chandra Images and False Color http://chandra.harvard.edu/photo/false_color.html

2. In the activity, the students will develop an image for the supernova remnant Cassiopeia A (Cas A). Before conducting the activity, the students should be exposed to the basic components of supernova remnants. There are several images of supernova remnants, including Cas A, at the Chandra web site (http://chandra.harvard.edu/photo/category/snr.html). Also, below is an image and feature discussion of Cas A that the teacher should review before conducting the activity.

3. One of the main purposes of this activity is to show how numerical data from Chandra is converted to images of astronomical objects. A "Chandra Chronicles" article, titled "A River of Data Flows Through the CIAO Waterworks (http://chandra.harvard.edu/chronicle/0401/ciao_data.html)," discusses how computers assist Chandra scientists in converting numerical data to graphical images. The article includes pictures of the data received from Chandra, as well as a discussion of the software used to convert the data into images. Before conducting the activity, the teacher may find this background information helpful when assisting the students during the activity. Please note that the article is probably beyond the reading level of most middle school students, and therefore, would not make a suitable reading assignment for most middle school students.

4. The data the students are analyzing are the number of X-ray "photons" from the supernova remnant that are detected by Chandra. A photon is an individual packet of electromagnetic energy that makes up electromagnetic radiation. A discussion of how X-ray photons are produced can be found at http://chandra.harvard.edu/xray_astro/xrays.html.

5. Some of the data are intentionally missing. Again, this is a realistic challenge confronted by scientists. Depending on student ability you may use a variety of techniques ranging from estimation to statistical techniques to handle these data omissions.