NEOWISE Observations of Distant Active Long-period Comets C/2014 B1 (Schwartz), C/2017 K2 (Pan-STARRS), and C/2010 U3 (Boattini)

March 2024 • 2024AJ....167...99M

Authors • Milewski, Dave G. • Masiero, Joseph R. • Pittichová, Jana • Kramer, Emily A. • Mainzer, Amy K. • Bauer, James M.

Abstract • Hyperactive comet activity typically becomes evident beyond the frost line (∼3–4 au) where it becomes too cold for water-ice to sublimate. If carbon monoxide (CO) and carbon dioxide (CO₂) are the species that drive activity at sufficiently large distances, then detailed studies on the production rates of these species are extremely valuable to examine the formation of the solar system because these two species (beyond water) are next culpable for driving cometary activity. The NEOWISE reactivated mission operates at two imaging bandpasses, W1 and W2 at 3.4 μm and 4.6 μm, respectively, with the W2 channel being fully capable of detecting CO and CO₂ at 4.67 μm and 4.23 μm in the same bandpass. It is extremely difficult to study CO₂ from the ground due to contamination in Earth's atmosphere. We present our W1 and W2 photometry, dust measurements, and findings for comets C/2014 B1 (Schwartz), C/2017 K2 (Pan-STARRS), and C/2010 U3 (Boattini), hereafter, B1, K2, and U3, respectively. Our results assess CO and CO₂ gas production rates observed by NEOWISE. We have determined: (1) comets B1 and K2 have CO₂ and CO gas production rates of ∼10²⁷ and ∼10²⁹ molecules s^‑1, respectively, if one assumes the excess emission is attributed to either all CO or all CO_2; (2) B1 and K2 are considered hyperactive in that their measured Af ρ dust production values are on the order of ≳10³ cm; and (3) the CO and CO₂ production rates do not always follow the expected convention of increasing with decreased heliocentric distance, while B1 and K2 exhibit noticeable dust activity on their inbound leg orbits.

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Joe Masiero

Associate Scientist