It is the brightest star in the Christmas Tree open cluster in the area catalogued as NGC 2264.
S Monocerotis A is a spectroscopic binary system with an eccentric orbit of about 112 years.
[19] It is also an irregular variable star with a range of less than a tenth of a magnitude.
[6] The distance to S Monocerotis and NGC 2264 has been derived in various ways, including dynamical parallax and isochrone fitting.
These consistently give estimates of 700 - 900 parsecs, although this is double the likely distance derived from the Hipparcos parallax measurements.