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tokens: May 2 (chosen arbitrarily) and are integrated using a Bulirsch–Stoer integrator, considering the gravitational perturbations from the eight major planets (with the Earth–Moon system represented by a single point mass at the barycenter of the two bodies), relativistic effects, and β = 0.001 particles, radiation pressure, and Poynting–Robertson drag. The particle representing Phaethon and all other dust particles are considered to be massless and do not interact with each other. We find that it only takes about 250 years (∼200 orbits) for particles to spread to the entire orbit of Phaethon (Figure 1 , left panel). The timescale is much shorter (∼30 years) for β = 0.001 particles under cometary ejection. The definition adopted here is the “encircling limit” described in Ye et al. ( 2016 , Section 3): meteoroids have spread to most of the orbit of the parent when the standard deviation of their mean anomalies σ ( M ) has reached 60°. The mathematical consideration is that 99.7% of the meteoroids have spread to half-orbit, or 180° in mean anomaly, assuming a Gaussian distribution along the orbit. (One may wonder why we do not choose 360° in mean anomaly instead of 180°. The reason is that σ ( M ) becomes highly sensitive to regional overdensities when meteoroids are quasi-evenly distributed along the orbit or , as reflected in the figure, and is no longer a good indicator of the dispersion of meteoroids along the orbit.) Figure 1. Evolution of particles ejected under different ejection mechanisms, cometary or gravitational escape. Left panel: standard deviation of mean anomalies of simulated particles, σ ( M ); the encircling limit at σ ( M ) = 60° follows the definition in Ye et al. ( 2016 ) (described in the main text). Right panel: along-orbit distance of the center of the particles (represented by the mean of the mean anomaly, ) to Phaethon. Regardless of the driving mechanism and size ( β ) of the particle, it only takes a small number of orbits for the bulk of the ejecta to spread to significant distances from Phaethon (∼0.1 au). This means that if any materials larger than typical meteor sizes (see below for more on meteor-sized particles) were recently ejected, they could be closer to the Earth than Phaethon itself during their late 2017 approach to the Earth and are potentially detectable using existing facilities. Examination of the existence of such ejecta will therefore provide a useful diagnosis as to recent activity of Phaethon that is otherwise irretrievable. This will also provide useful information for the design of any Phaethon-bound spacecraft like DESTINY + . We find that β = 0.001 particles quickly drift away from Phaethon (Figure 1 , right panel). This radiation-driven process is very fast due to the extreme orbit of Phaethon, with the along-orbit recession rate being approximately 0.1 au yr −1 . This means that it takes less than an orbit for small particles to drift to different locations of the orbit and effectively