New images of comet NEOWISE (C/2020 F3) show rapidly expanding spiral features in its coma produced by the rotation of its 5-km (3-mile) wide nucleus.
C/2020 F3 (NEOWISE) was discovered on March 27, 2020 by NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) mission.
The object is the brightest comet visible from the northern hemisphere since 1997’s Hale-Bopp comet.
C/2020 F3 (NEOWISE) made its close approach to the Sun on July 3, 2020, and is now heading back to the outer reaches of the Solar System, not to pass through our neighborhood again for another 7,000 years.
A team of astronomers, led by Jagiellonian University’s Dr. Michal Drahus and Dr. Piotr Guzik, used the Gemini Multi-Object Spectrograph (GMOS-N) on the Gemini North telescope on Hawaii’s Maunakea to observe the materials escaping from the comet over time.
The observations took place between July 28 and August 10, 2020, and were limited by the comet’s relatively close proximity to the Sun and the resulting short observing windows.
The GMOS-N images allowed the astronomers to determine the rotation of C/2020 F3 (NEOWISE) to excellent accuracy (rotation period of 7.58 hours) 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,” the astronomers said.
“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 we think is happening in the Gemini images,” they said.
“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.”
The researchers reported their observations this month in the Astronomer’s Telegram.
Michal Drahus et al. 2020. Rotation of Comet C/2020 F3 (NEOWISE). ATel # 13945