Research › Night
This page features research covering objects far enough away from the Sun to be studied with telescopes under dark skies.
Icy Dust from a Fresh Comet, C/2017 K2
Unlike returning comets, those arriving in the inner solar system from the Oort Cloud for the first time tend to appear much brighter before than after passing by the Sun, a sign of thermal processing of their surfaces from solar heating. The physical mechanism for this fading remains uncertain, but could conceivably involve an observable alteration of dust properties. Zhang et al. (2022; PSJ, 3, 135) used the Hubble Space Telescope to take a close look at one such fresh comet, C/2017 K2 (PANSTARRS), and found its visible dust to be comprised largely of what appear to be micron-sized water ice grains. This result provides a baseline for comparison with future observations constraining post-heating dust properties.
Probing the Kuiper Belt with Occultations
Kilometer-sized objects in the Kuiper Belt, similar in size to most comets, are too faint to be directly found by modern telescopes. The population of such objects, however, can still be probed by monitoring background stars for brightness fluctuations caused by the diffraction of starlight when these unseen objects serendipitously pass in front of those stars. Zhang et al. (2023; AJ, 166, 242) performed such an occultation survey using the specially-designed CHIMERA instrument on the Palomar Hale Telescope, and set upper bounds on the number density of these objects, but a more sensitive survey will be needed for conclusive detections of any true occultations.