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Protostellar outflows and jets play a vital role in star formation as theycarry away excess angular momentum from the inner disk surface, allowing thematerial to be transferred toward the central protostar. Theoretically, lowvelocity and poorly collimated outflows appear from the beginning of thecollapse, at the first hydrostatic core (FHSC) stage. With growing protostellarcore mass, high-density jets are launched which entrain an outflow from theinfalling envelope. Until now, molecular jets have been observed at highvelocity ($\gtrsim$ 100 km/s) in early Class\,0 protostars. We, for the firsttime, detect a dense molecular jet in SiO emission with small-velocity ($\sim$4.2 km\,s$^{-1}$, deprojected $\sim$ 24 km\,s$^{-1}$) from sourceG208.89-20.04Walma (hereafter, G208Walma) using ALMA Band\,6 observations. Thisobject has some characteristics of FHSCs, such as a small outflow/jet velocity,extended 1.3\,mm continuum emission, and N$_2$D$^+$ line emission. Additionalcharacteristics, however, are typical of early protostars: collimated outflowand SiO jet. The full extent of the outflow corresponds to a dynamical timescale of $\sim$ 930$^{+200}_{-100}$ years. The spectral energy distributionalso suggests a very young source having an upper limit of T$_{bol}$ $\sim$ 31K and L$_{bol}$ $\sim$ 0.8 L$_\sun$. We conclude that G208Walma is likely inthe transition phase from FHSC to protostar, and the molecular jet has beenlaunched within a few hundred years of initial collapse. Therefore, G208Walmamay be the earliest object discovered in the protostellar phase with amolecular jet.

astrophysical journal/the astrophysical journal

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Evidence for  a Molecular Jet Launched at an Unprecedented Early Phase of Protostellar  evolution