Observational History
Since 1963, Gamma Orionis was included with a set of bright stars that astronomers employ as a luminosity standard. These are used for comparison with other stars to check for variability, and so by definition, the apparent magnitude of Gamma Orionis was set to 1.64. However, when an all-sky photometry survey was carried out in 1988, this star was itself found to be variable. It ranges in apparent magnitude from 1.59 to 1.64.
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“A man will not need to study history to find out what is best for his own culture.”
—Henry David Thoreau (1817–1862)