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Doing Science

Unit One: Investigating Motions of the Sky
Doing Science

2. Looking Deeper in the Sky

In an earlier "Doing Science" you counted stars in the night sky using the Palomar Sky Survey. These images provide a good overview of the brighter stars and other objects in space and provide coverage of nearly the entire sky. Several telescopic surveys have been conducted in small areas of the sky, but with much longer exposure times—30 to 50 hours or more for a single exposure. These long exposure times bring out much fainter objects so these long exposure images are called "Deep Looks." You will compare what you can see in the survey images with what is visible in the Deep Looks. You will then compare Deep Looks into the Milky Way with one near the Milky Way's "north pole."

Get the Orion Deep Wide Field at the Astronomy Picture of the Day site for January 6, 2007: This image is in the middle of the constellation of Orion and includes part of the Milky Way. Follow the links to the largest available version of the image and download it (note: the file size is about 2 MB). This image is about 5 x 8 degrees, and its center is near RA 5h 45m, Dec �4°. Go to the Palomar Sky Survey and obtain a 1°- square image centered on the same coordinates.

Next, choose one of the following fields near the Milky Way's "north pole" and download one of the images from:

  1. NOAO Deep Wide Field: a 1.15 deg square image (about 1/9 of the whole field) can be found at: Select either the 776 Kb or the 9.5 MB image. The center coordinates of this image are: RA = 14h 32m 05.7120s, DEC = +34o 16' 47.496'' (J2000).
  2. Deep Lens Survey: Select a sub-frame image about 2/3 of a degree square (about 1/9 of the whole field) from Field 4 at: Each sub-frame is about 2 MB. The center coordinates of Field Four are: RA 10h 52m 00s, Dec �05° 00m 00s (J2000).
  3. Go to the Palomar Sky Survey and obtain a 1°-square image centered on the same coordinates as that of the field you choose.

    Compare the Orion Deep Wide Field image with the Palomar Survey image of the same field. What additional features are visible in the Deep Look image? Make a list of the features you see in each. Repeat your comparison, this time looking at the Deep Look image you selected near the Milky Way's north pole and the Palomar Survey image of the same field. Now compare the two Deep Look images and your two lists of objects. How are they different? Why do you think they are different? How does the number of faint objects vary across each of the Deep Look images? Is it roughly constant or does it change?

    Your Challenge:

    1. Make a poster or power point presentation showing your different Deep Look images, your lists of objects, and your summaries of how and why they are different.
    2. Repeat your analysis with another Deep Look field. You can use the one above that you didn't choose, or you can choose one of the Hubble Deep Fields:

      Hubble Deep Field:, Image Center: RA 12:36:49.4, Dec +62:12:58.0. Select as large an image as possible. The largest is 2 MB.

      Hubble Deep Field South: Image Center: RA 22h 32m 56.22s, Dec -60d 33' 02.69. Select as large an image as you can download. The largest is 22.2 Mb.

      Hubble Ultra Deep Field: Image Center is: RA 3h 32m 40s, Dec �27d 47m 29s. Select as large an image as you can download. The largest is 60 Mb.

      All of these Deep Looks are located away from the Milky Way. Why do you think that is the case?