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Sky Surveys
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Sky Surveys Project - Teachers' Guide

This project lets students look at other attempts to map the universe, and compare those maps to the SDSS's map. Students will see that information from each the surveys complements the others, and taken together, all the surveys help us more completely understand the universe.

Project Goals

By the end of this project, students should be able to:

  • Compare images from the SDSS and POSS, and explain the differences
  • Find supernovae by comparing SDSS and POSS images
  • Describe the advantages of looking at infrared, x-ray, and visual images
  • Describe what types of objects are likely to give off x-rays
  • Find visual counterparts to x-ray sources
  • Explain how different data sources complement one another to give a better picture of the universe

Background Knowledge

Students should have some familiarity with the electromagnetic spectrum. They will need to know the difference between infrared light, visible light, and x-rays. If the students know how to use a simple image processing program, it would be useful to zoom in on the supernovae.

Project Structure

This project compares images from SDSS to images from three other sky surveys: the Palomar Sky Survey (POSS), an older visible light survey, the Two Micron All Sky Survey (2MASS), an infrared survey, and the Röntgen satellite (ROSAT), an x-ray survey.

The Palomar Sky Survey (POSS) is an older visual survey. It covers a lot of the same area of the sky as the SDSS. After a qualitative comparison, students try to find some of the supernovae discovered by the SDSS by comparing SDSS images to POSS images.

2MASS is an all-sky survey currently being carried out in the infrared. About half the sky is currently available to search on the 2MASS web site. Students will notice a couple of things about 2MASS images. First, dust lanes are invisible in the infrared. Dust is transparent to infrared light but opaque to visible light Second, you can see cooler objects in the infrared, so you typically see objects in the infrared you can't see in the visible light.

ROSAT is an X-Ray survey. Students will look at some very high-energy sources in this section of the project. They will find the optical counterpart to objects in the ROSAT survey by using SDSS images.

The final challenge, Exercise 5, should not be done during class, although you may wish to offer extra credit for completing it. Interested students should do the exercise on their own; it is designed to take several hours to complete. Students should look up information on a single object using as many data sources as possible, then try to deduce as much as they can about the object from what they find.

Questions and Exercises

Questions are designed to get students thinking about the way scientists work. Exercises are designed to get students to explore using SkyServer data to solve problems. For answers to all questions, click here. To see the answers, you must have the Adobe Acrobat PDF viewer installed on your computer. Acrobat is available for free download from Adobe's web site.

Students should be evaluated based on their written answers to the questions and exercises. You may use our sample scoring rubric or develop your own. If you use our scoring rubric, print out a copy for each student and attach it when you return his or her work.

For specific information on any part of the project, click Next.