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Blue Snowball

 bluesnowballtinybr.jpg (5460 bytes)   NGC 7662, The Blue Snowball, in Andromeda. 
Right Ascension:   23 25 54.00,   Declination:   + 42 32 6.02      Equinox: 2000.00

Is it really blue?

This planetary nebula is similar to the ring nebula.  There is a central star which has puffed out its outer layers and then has collapsed to a very very hot dwarf star about the size of Earth! 

Investigate this nebula by displaying the images taken with R, V and B filters, showing portions of the red, green, and blue light emitted by the nebula and its central star.  Compare the brightness of the nebula in each filter.  Compare the brightness of another star in each filter.   Combine the images to create a composite. 

bluesnowballrvbstar.jpg (8016 bytes)

Open n7662r30.fts   This is the R filtered image.  It was taken for 30 seconds.  Display with the red palette.

Open n7662v45.fts  This is the V filtered image.  It was taken for 45 seconds.  Display with the green palette.

Open n7662b90.fts  This is the B filtered image.  It is a combination of two B images each taken for 45 seconds. Therefore this image represents the light from a 90 second exposure.  Display with a blue palette.

Why aren't the exposure times equal?  Each of the images are for different exposure times because the camera is least sensitive in blue and most sensitive in red.  By imaging at this ratio of exposure times, we approximately balance the color much better than if we had equal exposure times.    Also, the  images have been shifted so it will be easy to add them together.  


What is the real color of NGC7662, the Blue Snowball?  Is it really blue?  Use Aperture to compare the brightness of the R, V, and B filtered images. (The R filter allows red light to pass; the V filter allows green light to pass; the B filter allows blue light to pass.)

Data Tools, Aperture
    Radius 30
    Sky Radius 60

  1. The nebula is brightest in which filter?  __________
  2. Describe the real color(s) of NGC7662?

    _______________________________________
  3. How would you name this nebula?  Why?

    _______________________________________

What color is the star which is North and East of the Blue Snowball?  Compare the brightness of the star in the R, V, and B filtered images.

Data Tools, Aperture
    Radius 5
    Sky Radius 10

  1. The star  (x____, y____) is brightest in which filter?  __________
  2. Describe the real color(s) of this star.

    _______________________________________

bluesnowballtinygrey.jpg (5428 bytes)  Combine the three images to see all the light gathered by the filters.

1.  Click on n7662r30.fts
2.  Go to Manipulation Add, Displayed image, Select n7662v45.fts.  Click display results in a new window.
3.  Click on the new window.  Again, go to Manipulation Add, Displayed image, Select n7662b90.fts.  Click OK.
4.  Save this new  image as n7662rvb.fts.


HOU Educators:  Download .fts  images of NGC 7662, the Blue Snowball.
These images were taken for Martha Bright and her students at the Hubble Middle School in Wheaton, Illinois.

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01/31/2000

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