High Resolution Thermal Infrared Imaging of 3200 Phaethon

Abstract

We present thermal infrared observations of the active asteroid (and Geminid meteoroid stream parent) 3200 Phaethon using the Very Large Telescope. The images, at 10.7 micron wavelength, were taken with Phaethon at its closest approach to Earth (separation 0.07 AU) in 2017 December, at a linear resolution of about 14 km. We probe the Hill sphere (of radius 66 km) for trapped dust and macroscopic bodies, finding neither, and we set limits to the presence of unbound dust. The derived limits to the optical depth of dust near Phaethon depend somewhat on the assumed geometry, but are of order 1e-5. The upper limit to the rate of loss of mass in dust is 14 kg/s. This is about 50 times smaller than the rate needed to sustain the Geminid meteoroid stream in steady state. The observations thus show that the production of the Geminids does not proceed in steady state.

33 pages, 7 figures

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• Continued PSP/WISPR Observations of a Phaethon-related Dust Trail
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• Thermal Alteration and Differential Sublimation Can Create Phaethons "Rock Comet" Activity and Blue Color
• Perihelion Activity of (3200) Phaethon Is Not Dusty: Evidence from STEREO/COR2 Observations
• Thermal radiation pressure as a possible mechanism for losing small particles on asteroids
• WISE/NEOWISE Multi-Epoch Imaging of the Potentially Geminid-related Asteroids: (3200) Phaethon, 2005 UD and 1999 YC
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