Most massive stars form in dense clusters where gravitational interactions with other stars may be common. The two nearest forming massive stars, the BN object and Source I, located behind the Orion Nebula, were ejected with velocities of ∼29 and ∼13 km s−1 about 500 years ago by such interactions. This event generated an explosion in the gas. New ALMA observations show in unprecedented detail, a roughly spherically symmetric distribution of over a hundred 12CO J=2−1 streamers with velocities extending from VLSR=−150 to +145 km s−1. The streamer radial velocities increase (or decrease) linearly with projected distance from the explosion center, forming a ‘Hubble Flow’ confined to within 5000 of the explosion center. They point toward the high proper-motion, shock-excited H2 and [Fe ii] ‘fingertips’ and lower-velocity CO in the H2 wakes comprising Orion’s ‘fingers’. In some directions, the H2 ‘fingers’ extend more than a factor of two farther from the ejection center than the CO streamers. Such deviations from spherical symmetry may be caused by ejecta running into dense gas or the dynamics of the N-body interaction that ejected the stars and produced the explosion. This ∼1048 erg event may have been powered by the release of gravitational potential energy associated with the formation of a compact binary or a protostellar merger. Orion may be the prototype for a new class of stellar explosion responsible for luminous infrared transients in nearby galaxies.
|Original language||English (US)|
|State||Published - Jan 7 2017|
- ISM: individual objects: Orion BN/KL
- ISM:jets and outflows
- Stars: formation
ASJC Scopus subject areas