Confirming the Explosive Outflow in G5.89 with ALMA

TL;DR

This study confirms the presence of an explosive molecular outflow in G5.89, similar to Orion, using high-resolution ALMA observations, revealing multiple filaments and shocks, and suggesting such events occur roughly every 100 years during massive star formation.

Contribution

First detection of an explosive outflow in G5.89 with detailed ALMA observations, expanding understanding of explosive phenomena in massive star formation regions.

Findings

Over 30 molecular filaments with Hubble-like expansion.

Detection of strong shocks near the explosion origin.

Estimated occurrence rate of explosive events is about once every 100 years.

Abstract

The explosive molecular outflow detected decades ago in the Orion BN/KL region of massive star formation was considered to be a bizarre event. This belief was strengthened by the non detection of similar cases over the years with the only exception of the marginal case of DR21. Here, we confim a similar explosive outflow associated with the UCH$_{\rm II}$ region G5.89$-$0.39 that indicates that this phenomenon is not unique to Orion or DR21. Sensitive and high angular resolution ($\sim$ 0.1$''$) ALMA CO(2$-$1) and SiO(5$-$4) observations show that the molecular outflow in the massive star forming region G5.89$-$0.39 is indeed an explosive outflow with an age of about 1000 yrs and a liberated kinetic energy of 10$^{46-49}$ erg. Our new CO(2$-$1) ALMA observations revealed over 30 molecular filaments, with Hubble-like expansion motions, pointing to the center of UCH$_{\rm II}$ region. In addition, the SiO(5$-$4) observations reveal warmer and strong shocks very close to the origin of the explosion, confirming the true nature of the flow. A simple estimation for the occurrence of these explosive events during the formation of the massive stars indicates an event rate of once every $\sim$100 yrs, which is close to the supernovae rate.