Time-sensitive observations of Chiron: a unique active Centaur beyond 15 AU
Abstract
Chiron is the one of the largest known Centaurs, i.e., inward-scattered objects from the Kuiper belt that reside in the giant planet region. As it was approaching aphelion at 18.8 AU in March 2021, Chiron experienced an outburst of cometary activity. A subsequent JWST observation in July 2023, obtained as part of a Cycle 1 GTO program, revealed evidence of methane and carbon dioxide outgassing and a perplexing absence of carbon monoxide emission. The unique spectral characteristics and extreme heliocentric distance of Chiron during its current active phase challenge our current understanding of distant cometary activity. Unfortunately, the July 2023 JWST spectrum does not have the requisite spectral resolution and sensitivity to enable proper assessment of Chiron's gas emission and coma properties. Continued photometric monitoring of Chiron since the 2021 outburst shows that its activity level is in a steady decline, and we propose to obtain DDT observations of Chiron during its next visibility window (November 2023-January 2024) to carry out timely intensive spectroscopic study before its activity subsides. We will leverage the high spectral resolution of the G395H grating to fully resolve the gas emission bands and derive precise constraints on the production rates. Accompanying exposures with the G235M grating will provide crucial information about the abundance of carbon dioxide ice on the surface and within the coma. The insights gleaned from these observations have the potential to reshape our fundamental understanding of the chemical composition and thermal evolution of distant planetesimals.
- Publication:
-
JWST Proposal. Cycle 2
- Pub Date:
- November 2023
- Bibcode:
- 2023jwst.prop.4621W