At the center of the Helix Nebula, a star late in its life sheds layers of its atmosphere. The star’s remaining heated core illuminates the surrounding gaseous shells, ionizing atoms and in turn producing light. In this three-color image, we capture this light which has been imprinted with the identities of the elements that emitted it: hydrogen-alpha (H𝛼), doubly ionized oxygen (OIII), and singly ionized sulfur (SII). These elemental snapshots, presented in red, green, and blue respectively, allow us to better view and understand the nebula’s structure.
Helix Nebula (NGC 7293) in H𝛼, [OIII] and [SII] by James Garland ’22Eleven 120 second exposures were taken in each filter with the Proline PL16803 CCD on the 16” telescope at Strawbridge Observatory. The exposures were aligned and stacked in AstroImageJ. The resulting three images were combined to make an RGB composite, which was adjusted for contrast and color balance. The original image captured a 30 x 30 arcminute field of view, roughly equivalent to the diameter of the Moon. Here, it has been cropped to a size of 27.6 x 27.6 arcminutes. The image was taken on the night of September 19, 2020.
