A Deep Search for Emission from “Rock Comet” (3200) Phaethon at 1 au

Abstract We present a deep imaging and spectroscopic search for emission from (3200) Phaethon, large near-Earth asteroid that appears to be the parent of strong Geminid meteoroid stream, using 4.3 m Lowell Discovery Telescope. Observations were conducted on 2017 December 14–18 when Phaethon passed only 0.07 au Earth. determine 3 ? upper level dust CN production rates 0.007–0.2 kg s ?1 2.3 × 10 22 molecules through narrowband imaging. A in broadband images taken SDSS r ? filter shows no 100 class fragments Phaethon’s vicinity. deeper but star-contaminated also sign down 15 m. Optical spectroscopy comet C/2017 O1 (ASASSN) as comparison confirms absence cometary lines yields levels CN, C 2 , ?10 24 –10 25 orders magnitude higher than constraint placed by imaging, due much narrower on-sky aperture spectrographic slit. show could provide an efficient way look weak gas near-extinct bodies near Earth, though these observations require careful interpretation. Assuming behavior is unchanged, our analysis DESTINY + mission, currently planning explore 2026, may not able directly detect coma.