The OMC1 BN/KL outflow, located immediately behind the Orion Nebula, may have been triggered

by the dynamic decay of a non-hierarchical system of massive stars that resulted in the formation of a

compact, AU-scale binary, or more likely, a protostellar merger (Bally et al. 2011, 2015). The event

ejected the ∼ 20 M binary or merger remnant (suspected to be radio source I), the ∼12 Solar-mass

BN object, and infrared source n, and released more than 1048 ergs of energy about 500 years ago.

I will present ALMA observations of CO and the continuum with 1" angular resolution and multi-

conjugate adaptive optics images at 0.06" resolution in the 2.12 μm H2 and 1.64 μm [FeII] emission

lines. Explosive outflows similar to Orion may be associated with the ejection of runaway stars, the

production of IR-flares with luminosities between novae and supernovae, and have profound feedback

impact on their parent molecular clouds. Massive protostars accreting at high rates develop AU-scale

photospheres that resemble red supergiants. Protostellar mergers may be relatively common in massive

star forming regions because of the large cross-sections of bloated massive protostars, the high stellar

volume density of forming clusters, and the dissipative nature of dense cloud cores and clumps.

References:

Bally, J., Ginsburg, A., Silvia, D., et al. 2015, A&A, 579, 130

Bally, J., Cunningham, N. J., Moeckel, N., et al. 2011, ApJ, 727, 113