Dust from Comet 209P/LINEAR during its 2014 Return: Parent Body of a New Meteor Shower, the May Camelopardalids

We report a new observation of the Jupiter family comet 209P/LINEAR during its 2014 return. The comet is recognized as a dust source of a new meteor shower, the May Camelopardalids. 209P/LINEAR was apparently inactive at a heliocentric distance r_h = 1.6 AU and showed weak activity at r_h <= 1.4 AU. We found an active region of <0.001% of the entire nuclear surface during the comet's dormant phase. An edge-on image suggests that particles up to 1 cm in size (with an uncertainty of factor 3-5) were ejected following a differential power-law size distribution with index q = -3.25 ± 0.10. We derived a mass-loss rate of 2-10 kg s^-1 during the active phase and a total mass of ≈5 × 10⁷ kg during the 2014 return. The ejection terminal velocity of millimeter- to centimeter-sized particles was 1-4 m s^-1, which is comparable to the escape velocity from the nucleus (1.4 m s^-1). These results imply that such large meteoric particles marginally escaped from the highly dormant comet nucleus via the gas drag force only within a few months of the perihelion passage.