R Monocerotis (R Mon) is a T Tauri variable in the constellation Monoceros. T Tauri stars ( TTS) are a class of variable Stars named after their prototype – T Tauri. Monoceros (məˈnɒsərəs Μονόκερος) is a faint Constellation in the Winter night sky surrounded by Orion to the west Gemini The apparent magnitude of R Mon varies between 10 and 12. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value
The star is located in a diffuse nebula called "Hubble's Variable Nebula" (NGC 2261). In Astronomy, diffuse nebulae is the general term for illuminated Nebulae The three types of diffuse nebulae are Reflection nebulae Emission 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 contain this star.
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