Observations of the isolated globule B335 with ALMA have yielded absorption features against the continuum that are redshifted from the systemic velocity in both HCN and HCO ^ { + } lines .
These features provide unambiguous evidence for infall toward a central luminosity source .
Previously developed models of inside-out collapse can match the observed line profiles of HCN and HCO ^ { + } averaged over the central 50 AU .
At the new distance of 100 pc , the inferred infall radius is 0.012 pc , the mass infall rate is 3 \times 10 ^ { -6 } M _ { \odot } yr ^ { -1 } , the age is 5 \times 10 ^ { 4 } years , and the accumulated mass in the central zone is 0.15 M _ { \odot } , most of which must be in the star or in parts of a disk that are opaque at 0.8 mm .
The continuum detection indicates an optically thin mass ( gas and dust ) of only 7.5 \times 10 ^ { -4 } M _ { \odot } in the central region , consistent with only a very small disk mass .