noirlab2021 — Photo Release

A Dizzying Show by Comet NEOWISE

Gemini Observatory images reveal striking details of our recent celestial visitor’s rotation

24 August 2020

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.

More information

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).

NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory), the US center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSFNRC–CanadaANID–ChileMCTIC–BrazilMINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawaiʻi, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O'odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.



Peter Michaud
NewsTeam Manager, NSF’s NOIRLab
Hilo, HI, USA
Tel: +1 808 936 6643

About the Release

Release No.:noirlab2021
Name:Comet NEOWISE
Facility:Gemini North


Comet NEOWISE Rotation Sequence (Images)
Comet NEOWISE Rotation Sequence (Images)


Comet NEOWISE Rotation Timelapse Sequence (annotated version)
Comet NEOWISE Rotation Timelapse Sequence (annotated version)
Comet NEOWISE Rotation Timelapse Sequence (clean version)
Comet NEOWISE Rotation Timelapse Sequence (clean version)