40 Eridani, in short terms, 40 Eri and named as Keid, is a triple star system in the constellation of Eridanus, it is located about 16.3 light-years away from the Sun.
The main star of the system, 40 Eridani A (Keid A) is easily visible to the naked eye. It is orbited by a binary star, two stars orbiting each other and both of them orbiting the main star. The star system was discovered on January 31, 1783, by astronomer William Herschel.