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The level of central segregation of Blue Straggler stars proved to be anexcellent tracer of the dynamical evolution of old star clusters (the so-called"dynamical clock"), both in the Milky Way and in the Large Magellanic Cloud.The $A^{+}$ parameter, used to measure the Blue Stragglers degree ofsegregation, has in fact been found to strongly correlate with the parentcluster central relaxation time. Here we studied the Blue-Straggler populationof two young stellar systems in the Small Magellanic Cloud, namely NGC 339(which is 6 Gyr old) and NGC 419 (with an age of only 1.5 Gyr), in order tostudy their dynamical state. Thanks to multi-epoch, high angular resolutionHubble Space Telescope observations available for both clusters, we tookadvantage of the stellar proper motions measured in the regions of the twosystems and we selected a population of likely cluster members, removing thestrong contamination from Small Magellanic Cloud stars. This enabled us tostudy, with unprecedented accuracy, the radial distribution of Blue Stragglersin these two extragalactic clusters and to measure their dynamical age. Asexpected for such young clusters, we found that both systems are poorly evolvedfrom the dynamical point of view, also fully confirming that the $A^{+}$parameter is a sensitive "clock hand" even in the dynamically-young regime.

Blue Stragglers as tracers of the dynamical state of two clusters in the Small Magellanic Cloud: NGC 339 and NGC 419