Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. EF Eridani is a variable star of the type known as polars, AM Herculis stars, or magnetic cataclysmic variable stars. Historically it has varied between apparent magnitudes 14.5 and 17.5, although since 1995 it has generally remained at the lower limit. The star system consists of a white dwarf star with a substellar massed former star in orbit. The substellar mass in orbit around the white dwarf is a star which lost all of its gas to the white dwarf, except what remains, a 0.05 solar mass ball, which is too small to continue fusion, and does not have the composition of a super-planet, brown dwarf, or white dwarf. There is no category for such a stellar remnant.