Mass shedding activities of Asteroid (3200) Phaethon enhanced by its rotation

Abstract

Asteroid (3200) Phaethon, a B-type asteroid, has been active during its perihelion passages. This asteroid is considered to be a source of the Geminid meteor stream. It is reported that this asteroid is spinning at a rotation period of $3.60hr$ and has a top shape (an oblate body with an equatorial ridge) with a mean equatorial diameter of $6.25km$. Here, we report that Phaethon's rotation state may be close to or above its critical rotation period when the bulk density is $0.5-1.5g/c{m}^3$ (a typical bulk density of a B-type asteroid). We found that in this condition, the structure of Phaethon is sensitive to failure unless the cohesive strength is $\sim 50Pa-\sim 260Pa$. This result implies that if there are some surface processes driven by, for example, thermal waves, large-scaled deformation may happen and cause mass shedding. From this interpretation, we propose the processes that produced the Geminid meteor stream in the past and dust tails recently. Phaethon initially rotated at a spin period shorter than the current period. The magnitude of structural deformation at this stage was higher than the present spin condition, and a large mass shedding event, i.e., the Geminid meteor stream, occurred. After this deformation process, the body became more oblate, and its spin slowed down. At this point, while the spin was high enough for the body to have mass shedding events, the magnitude of these events became small.

arXiv comment10 pages, 4 figures, 1 table; Accepted for publication in ApJL

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• Hayabusa2 Extended Mission: New Voyage to Rendezvous with a Small Asteroid Rotating with a Short Period
• Sodium Brightening of (3200) Phaethon Near Perihelion
• Thermal Alteration and Differential Sublimation Can Create Phaethons "Rock Comet" Activity and Blue Color
• Seasonally Varying Outgassing as an Explanation for Dark Comet Accelerations
• WISE/NEOWISE Multi-Epoch Imaging of the Potentially Geminid-related Asteroids: (3200) Phaethon, 2005 UD and 1999 YC
• The common trend of saltation particles on the surface of fast-rotating asteroids
• Surface dynamics and geophysical environment of asteroid (3200) Phaethon