2006AJ....131.2327J

We present a new observation that conclusively reveals the cometary nature of the planet-crossing asteroid 2003 WY₂₅through the detection of a weak optical coma. This observation strongly supports the identification of 2003 WY₂₅with the lost comet D/1819 W1 (Blanpain) made previously on the basis of dynamical similarity. It also shows that 2003 WY₂₅is a continuing but weak source of particles for the Phoenicid meteor stream with a mass injection rate into the stream of ∼10^–2 kg/s. This is too small to supply the estimated 10¹¹ kg stream mass on any plausible timescale, suggesting that the mass injection into the stream may be episodic and/or involve additional sources. We estimate a nucleus radius near 160 m and find that, consistent with estimates for other meteor streams, the ratio of the nucleus mass to the stream mass is of order unity. We find that 2003 WY₂₅is the smallest cometary nucleus yet observed.