Levay at his alma mater:
Indiana University's Kirkwood
courtesy K. Kalinowski)
experience with the planetary nebula NGC 6369 was a few
years ago, when astronomer Howard Bond asked me to help
him put together a color image from some Hubble data he
had made. He was working on a large study of the central
stars of planetary nebulae. We had two images available,
taken through filters of different colors (broad bands of
visible/green-yellow and near-infrared/reddish). These images
provided the information Dr. Bond needed to study the star
at the center of this nebula.
able to produce a color composite
image, though it was not spectacular. The image did
hint at some interesting structures but we were not able
to show these with a full color range like we have been
able to do with other nebulae. In addition, some of the
nebula "fell off" the edge of the camera's field
of view because the observations were aimed at the central
star rather than the nebula as a whole.
time I thought it would be interesting and fun to make Hubble
observations that would show this object with a greater
range of subtlety and color, and hopefully to see more detailed
structure. Through the Hubble Heritage project we were able
to get some additional Hubble observations a few years later.
This time we used filters that isolated the light of specific
chemical elements: Nitrogen, Hydrogen, and Oxygen. We knew
from studies of other nebulae that much of the light probably
was being emitted by these elements. We planned exposures
that would produce the best images of the nebulosity. We
also pointed the telescope so the whole nebula fell within
the field of view of the camera.