The Michelson stellar interferometer is one of the earliest astronomical interferometers built and used. The interferometer was proposed by Albert A. Michelson in 1890, following a suggestion by Hippolyte Fizeau.
The first such interferometer built was at the Mount Wilson Observatory, making use of its 100-inch (~250 centimeters) mirror. It was used to make the first-ever measurement of a stellar diameter, by Michelson and Francis G. Pease, when the diameter of Betelgeuse was measured in December 1920. The diameter was found to be 240 million miles (~380 million kilometers), about the size of the orbit of Mars, or about 300 times larger than the Sun.
Scheme of the Michelson stellar interferometer.
A 20-foot (~6 meters) Michelson interferometer mounted on the frame of the 100-inch (~250 cm) Hooker Telescope, 1920.
The Hooker Telescope interferometer on display at the Mount Wilson observatory, 2023.
