Orion variable

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Orion variables are variable stars which exhibit irregular and eruptive variations in their luminosity and are typically associated with diffuse nebulae. It is thought that these are young stars which will later become regular, non-variable stars on the zero-age main sequence. Brightness fluctuations can be as much as several magnitudes.

T Tauri stars are Orion variables exhibiting characteristic fluorescent violet emission lines from singly ionized Iron (FeII) in their star spectra, and also emission from Lithium, a metal that usually is destroyed by the nuclear fusion in the stars.

Of this diverse class of stars, some Orion variables may exhibit a small amplitude (up to 1 magnitude) periodic variation, some are characterized by abrupt fadings, and some show spectral characteristics indicating mass downfall upon the star. Many of these characteristics may occur in any one Orion variable.