The data in this image used a narrow-band filter that allowed H-alpha emission through to the telescope’s detectors. The particular filter, called F657N (F for filter, N for narrow, and 657 for the wavelength in nanometers) or the H-alpha filter, lets through light very close to the 656.46 nanometer H-alpha line’s wavelength. It reveals pinkish star-forming regions in the galaxy.
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