Doubly ionized oxygen: Difference between revisions

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'''Doubly ionized oxygen''' (also known as '''<nowiki>[O III]</nowiki>''') is a [[forbidden line]] of the [[ion]] [[oxygen|O]]²⁺. It is significant in that it emits light in the green part of the spectrum primarily at the frequency 500.7 nanometres (nm) and secondarily at 495.9 nm. Concentrated levels of <nowiki>[O III]</nowiki> are found in [[diffuse nebula|diffuse]] and [[planetary nebula|planetary]] nebulae. Consequently, narrow [[band-pass filter]]s that isolate the 501 nm and 496 nm wavelengths of light are useful in observing these objects, causing them appear at higher contrast against the filtered and consequently blacker background of space where the frequencies of <nowiki>[O III]</nowiki> are much less pronounced.