Gemini Observatory images reveal striking details of our recent celestial visitor’s rotation.
When Comet NEOWISE (C/2020 F3) sped through the inner Solar System during the middle of 2020, astronomers and the general public watched in awe as this “dirty snowball” shed gas and dust into space, producing a striking show visible to the naked eye. Close-up observations, led by Michal Drahus and Piotr Guzik of Jagiellonian University in Krakow, used the international Gemini Observatory, a Program of NSF’s NOIRLab, to observe the materials escaping from the comet over time. One set of observations, obtained on 1 August 2020 from the Gemini North telescope on Hawai‘i’s Maunakea, displays a spiraling stream of molecular gas that reveals the rotation of the comet’s nucleus. The timelapse sequence, compressed to only a few seconds, represents about one fifth of the approximately 7.5-hour rotation period of the comet.
The observations, obtained under a research program to explore the rotational dynamics of the comet, took place over several evenings, and were limited by the comet’s relatively close proximity to the Sun and the resulting short observing windows. The Gemini observations allowed the researchers to determine the rotation of the comet to excellent accuracy and to look for changes in the rotation rate.
Comets consist of ices, rocks, and dust left over from the formation of our Solar System. Some comets follow highly elongated orbits which send them close to the Sun where they warm up and cause the frozen gases to vaporize, releasing molecules and debris into space. It is thought that most comets release gasses in geyser-like jets and that is what researchers think is happening in the Gemini images. As the vaporized material erupts from the comet its rotation causes it to appear to spiral outward, much like the water from a spinning garden hose. The very same material impacts the comet’s rotation causing its nucleus to spin-up or spin-down, though for most comets, the effect is too weak to detect.
This research was reported in an Astronomers Telegram.
The team is composed of Michal Drahus (Jagiellonian University in Krakow), Piotr Guzik (Jagiellonian University in Krakow), Andrew Stephens (Gemini Observatory), Steve B. Howell (NASA Ames Research Center), Stanislaw Zola (Jagiellonian University in Krakow), Mikolaj Sabat (Jagiellonian University in Krakow) and Daniel E. Reichart (University of North Carolina at Chapel Hill).
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Images of Comet NEOWISE obtained with Gemini North on Hawai‘i’s Maunakea on the night of 1 August 2020. This sequence was obtained using the Gemini Multi-Object Spectrograph (GMOS) with the 468/8 nm filter and digitally enhanced using a dedicated algorithm. The field of view is 2 arcminutes across.Credit: International Gemini Observatory/NOIRLab/NSF/AURA/M. Drahus/P. Guzik
NEOWISE rotation timelapse animation. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/M. Drahus/P. Guzik/J. Pollard
The timelapse sequence of eight digitally enhanced images reveals the rotation of Comet NEOWISE using data from the international Gemini Observatory’s Gemini North telescope on Hawai‘i’s Maunakea. The images were obtained on 1 August 2020 using the Gemini Multi-Object Spectrograph over a period of 1.5 hours. In this sequence, the set of eight images are looped nine times.. Credit: International Gemini Observatory/NOIRLab/NSF/AURA/M. Drahus/P. Guzik/J. Pollard
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