Cometary Science Newsletter

October 2020
Michael S. P. Kelley (

JWST Cycle 1 GTO Update: 116P/Wild 4 and 238P/Read

The James Webb Space Telescope's (JWST) Guaranteed-Time Observation (GTO) program includes observations of comets in Heidi Hammel's "Solar System Observations with the James Webb Space Telescope" GTO project. Target selection is based on comet availability in Cycles 1 and 2. Given that JWST's revised target launch date is now 2021 October 31, the Space Telescope Science Institute has approved 116P/Wild 4 and 238P/Read as new targets for the GTO project. The target of opportunity Oort cloud comet remains unchanged. These data will be provided with no proprietary period in order to facilitate plans for future comet observations with the Webb. See CSN Issue 20, or JWST proposals 1252 and 1253 for details.

Mike Kelley, Univ. Maryland
Stefanie Milam, NASA GSFC
Heidi Hammel, AURA

Refereed Articles

Abstracts of articles in press or recently published. Limited to 3000 characters.

Resolving color differences of comet 41P/Tuttle-Giacobini-Kresák

  • Luk'yanyk, I. 1
  • Zubko, E. 2
  • Videen, G. 2,3
  • Ivanova, O. 1,4,5
  • Kochergin, A. 6,7
  1. Astronomical Observatory, Taras Shevchenko National University of Kyiv, Ukraine
  2. Humanitas College, Kyung Hee University, South Korea
  3. Space Science Institute, USA
  4. Astronomical Institute of the Slovak Academy of Sciences, Slovak Republic
  5. Main Astronomical Observatory of National Academy of Sciences, Ukraine
  6. School of Natural Sciences, Far Eastern Federal University, Russia
  7. Institute of Applied Astronomy of RAS, Russia

Three different measurement campaigns have resulted in three drastically different sets of color measurements of Comet 41P/Tuttle-Giacobini-Kresák, ranging from a strongly red to a strongly blue color. Although the color slope is normalized to the wavelength range between the filters used, this only serves to partially normalize the resulting color, as the reflectance of cometary dust has a very strong dependence on particle absorption, which may change significantly over the wavelength range of measurement. We demonstrate that the different measurements are physical and are consistent with real materials; for example, we are able to reproduce the color measured during one epoch in which both strong blue and red color slopes were measured almost simultaneously in different filter sets with the mineral dust pyroxene. Such measurements with different filter sets serve as an additional constraint in modeling dust properties.

Astronomy & Astrophysics (In press)

DOI: 10.1051/0004-6361/202038893