  The radial extent of millimetre dust in protoplanetary discs is often far
smaller than that of their gas, mostly due to processes such as dust growth and
radial drift. However, it has been suggested that current millimetre continuum
observations of discs do not trace their full extent due to limited
sensitivity. In this Letter, we present deep (19 $\mu$Jy beam$^{-1}$) moderate
resolution (0.37") ALMA observations at 1 mm of the nearest protoplanetary
disc, TW Hya. Using the visibility analysis tool `frank', we reveal a
structured millimetre intensity distribution out to 100 au, well beyond
previous estimates of 60-70 au. Our analysis suggests the presence of a new
millimetre continuum gap at 82 au, coincident with similar features seen in
optical/near-infrared scattered light and millimetre molecular line
observations. Examination of the fit residuals confirms the presence of the
previously reported au-scale continuum excess at 52 au (P.A. = 242.5 degrees).
Our results demonstrate the utility of combining deep, moderate resolution
observations with super-resolution analysis techniques to probe the faintest
regions of protoplanetary discs.
