A clear detection of proper motion confirms that the claimed z 32 galaxy candidate, "Capotauro'', is a Y-type brown dwarf

The compact red source ``Capotauro'', discovered in deep JWST imaging in 2025, has been suggested as a possible galaxy candidate at redshift z 32 on account of its extreme NIRCam colours. However, given the lack of evidence that this source is spatially resolved, a very cool brown dwarf, at a distance consistent with the scale-height of the Milky Way stellar disc (500 pc), provides an alternative explanation of the observed photometry. Here we exploit new medium-band NIRCam imaging obtained 3.5 years after the discovery data to test this hypothesis. Using filter-dependent point-spread-function fitting, a robust local relative astrometric frame defined by 68 compact reference sources, and a joint four-image injection-recovery analysis, we show that Capotauro has moved by 132 plus or minus 20 mas over the 3.5-yr interval span of the observations, ruling out the possibility that it is an extragalactic source (galaxy, AGN, or supernova) at > 6 sigma. The observed apparent proper motion is (mu xi, mu eta)=(+9.4+6.4-4.8,-35.6+5.1-5.9) mas yr-1, or 37.6+5.5-5.6 mas yr-1 in total. Through comparison of its photometric spectral energy distribution with empirical templates, we find that Capotauro is best described as a brown dwarf of spectral type Y 1.0 plus or minus0.5 (T eff about350 K) at a distance of 730 plus or minus110 pc (although the existing data and spectral templates are insufficient to rule out an even colder, later-type brown dwarf). Capotauro is thus one of the most distant Y dwarfs found to date, as expected given its discovery in a deep JWST extragalactic survey field. This result demonstrates the value of multi-epoch imaging for identifying substellar contaminants among the most extreme photometric-redshift candidates.