Hubble observes Comet 41P reverse spin for first time
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Astronomers have, for the first time, observed a comet reversing its rotation, using data from NASA’s Hubble Space Telescope.
The phenomenon was recorded in Comet 41P/Tuttle-Giacobini-Kresák during its close approach to the Sun in 2017.
Planetary scientist David Jewitt of UCLA analysed the observations, with findings published in The Astronomical Journal on March 26.
Researchers found that the comet, which has a nucleus about 0.6 miles or 1 kilometre wide, slowed its spin significantly before coming to a complete stop and then rotating in the opposite direction.
This marks the first confirmed observation of such behaviour in a comet.
The reversal was driven by uneven gas jets formed as the comet approached the Sun. Heat caused frozen ices on the comet’s surface to sublimate, releasing gas in bursts that acted like small thrusters. These jets altered the comet’s rotation over time. Observations from NASA’s Swift Observatory showed that the comet’s spin rate slowed threefold in May 2017, while later Hubble images revealed it was rotating in reverse every 14 hours by December.
Jewitt compared the process to pushing a spinning merry-go-round in the opposite direction until it stops and begins turning the other way.
Scientists say the unusual spin behaviour could eventually lead to the comet’s destruction. As rotational forces increase, they may overcome the weak gravity holding the object together, potentially causing it to break apart.
The study also notes that the comet’s activity has declined significantly since its 2001 perihelion, likely due to depletion or burial of surface ice. Having spent around 1,500 years in its current orbit, researchers believe Comet 41P may be nearing the end of its life cycle.
