Determine the origin of the pre-brown-dwarf deficit

Determine whether the current scarcity of identified pre-brown dwarfs results from observational limitations or from the predominance of a non-star-like formation pathway, such as formation in circumstellar disks.

Background

The star-like formation scenario predicts that brown dwarfs and free-floating planets form through the collapse and fragmentation of molecular clouds, implying that pre-brown-dwarf and pre-free-floating-planet cores should exist. Only a few candidate pre-brown-dwarf cores have been identified, and their faintness and small size make them difficult to detect with single-dish observations.

The paper explains that ALMA2040 could conduct sensitive, wide-area surveys capable of identifying many such objects. A substantial population would support the star-like scenario, whereas a very small number would favor the planet-like scenario in which substellar objects form in circumstellar disks rather than as prestellar cores.

References

Thus, it is not clear yet if the current lack of pre-BDs is due to an observational effect or because the main formation pathway is not star-like: if BDs/FFPs are formed in circumstellar disks, very few pre-BDs should be found.

— Bridging the gap between stars and planets  (2610.22246 - Palau et al., 15 Oct 2026) in Section “Scaled-down version of the known phases of star formation,” subsection “Pre-BDs/FFPs: pre-substellar cores”