R Monocerotis

R Monocerotis (R Mon) is a T Tauri variable in the constellation Monoceros. The apparent magnitude of R Mon varies between 10 and 12 and the spectral type B8IIIe.

The star is located in a diffuse nebula called "Hubble's Variable Nebula" (NGC 2261). According to some astronomers, the "star" R Monocerotis is not more than a very bright concentration of gases within the nebula, and some sky catalogues and atlases do not list it as a star.