The nebula is illuminated by the star R Monocerotis (R Mon), which is not directly visible itself.

The first recorded observation of the nebula was by William Herschel on 26 December 1783, being described as considerably bright and 'fan-shaped'.

Jordan, allowing Hubble to use a blink comparator to search for any changes over time in the nebula.

[7] The star R Monocerotis has lit up a nearby cloud of gas and dust, but the shape and brightness slowly changes visibly even in small telescopes over weeks and months, and the nebula looks like a small comet.

[8] One explanation proposed for the variability is that dense clouds of dust near R Mon periodically block the illumination from the star.