A giant outburst was observed at the 22-GHz water maser frequency near the Orion-KL object (Abraham et al. 1979).
The light curve showed flux oscillations along several months with the degree of linear polarization
apparently correlated with the flux variations.
At its maximum, the maser intensity reached 2.4 x 10^6 Jansky in May of 1980 (Abraham et al. 1981).
The model proposed to explain the data (Abraham & Vilas-Boas 1994) considered that the maser source
consists of the central part of an edge-on protoplanetary ring associated with a forming protostar.
The model explains several features observed in VLBI observations, such as: the linear variation
of the maser velocity with position, the high brightness temperatures, etc.
Variability happens because of inhomogeneities in the ring in the form of dense clumps of material. A lower
limit of 15 solar masses for the central star, a diameter for the ring of 80 A.U. and a width of 1.6 A.U. were derived from
the model.