Questa immagine potrebbe avere delle imperfezioni perché è storica o di reportage.
The Dumbbell Nebula is a typical planetary nebula. Despite its class, the Dumbbell Nebula has nothing to do with planets. It consists of very rarified gas that has been ejected from the hot central star, now in one of the last evolutionary stages. The gas atoms in the nebula are excited (heated) by the intense ultraviolet radiation from this star and emit strongly at specific wavelengths. This image is the by-product of a technical test of some FORS1 narrow-band optical interference filters. They only allow light in a small wavelength range to pass and are used to isolate emissions from particular atoms and ions. In this three-color composite, a short exposure was first made through a wide-band filter registering blue light from the nebula. It was then combined with exposures through two interference filters in the light of double-ionized oxygen atoms and atomic hydrogen. They were color-coded as "blue", "green" and "red", respectively, and then combined to produce this picture that shows the structure of the nebula in "approximately true" colors. Release date October 7, 1998.
