Heritage team member Zolt Levay Photograph by Al Schultz (STScI)

Zolt Levay

(STScI)

I became intrigued by the Pencil Nebula while reading David Malin's magnificent book The Invisible Universe. I have been astounded by Dr. Malin's spectacular astronomical photographs for many years. His work has set very high technical and aesthetic standards for astronomical photography. These images have been a great inspriation to me personally, not only to encourage me to pursue astronomy, but also in my continuing work to produce images from the Hubble Space Telescope.

Running across the Pencil Nebula, I wondered what an image made with the Hubble Space Telescope might show. Hubble's ability to distinguish fine details has resulted in some surprises, including the varied and complex forms of nebulae. However, it is limited to a field of view much smaller than what Dr. Malin's image shows. Nevertheless, it seemed reasonable to assume that a Hubble image of the Pencil would show details not apparent in images from telescopes on the ground.

The Hubble Heritage Project is fortunate to be able to use the Hubble Space Telescope for a limited number of new observations of our choosing. The Hubble Heritage Team agreed that the Pencil Nebula would be a promising target, likely resulting in a beautiful image. We decided to use the recently-installed Advanced Camera for Surveys (ACS) for the first time for a Heritage image because of its overall finer resolution and its greater sensitivity than the older WFPC2 instrument. We asked Dr. Bill Blair for his help in planning our observations because he is an expert on this type of object (supernova remnants). In fact, he had some data on the Pencil, incluing brightness measurements, which he graciously shared with us, confirming that the nebula is quite faint. Nevertheless, we estimated that the the time we planned to devote to the observations would result in acceptable images.

We reconstructed the colors in this image from black and white images taken through various filters to isolate specific colors. We used two types of filters: reddish and bluish "narrow-band" filters to isolate light emitted mostly by hydrogen and oxygen as well as red, yellow-green and blue "broad-band" filters to render the colors of the stars fairly accurately. We tried to balance the contrast and brightness of the various exposures to show as much detail as possible over the whole nebula.

Hubble Heritage Team 2003 (Space Telescope Science Institute) Photograph by John Bedke (STScI/CSC)