Hubble Telescope Captures Comet Reversing Its Rotation for the First Time

For the first time, astronomers have witnessed a comet fully reversing its rotation. NASA's Hubble Space Telescope has recorded the behaviour of Comet 41P/Tuttle-Giacobini-Kresák during its close approach to the Sun in 2017. Planetary scientist David Jewitt of UCLA studied the Hubble observations and published his findings in The Astronomical Journal on March 26. The comet, which is a small icy body just 0.6 miles wide, significantly slowed down and came to a complete stop before reversing its rotation.

How Gas Jets Flip a Comet

According to the findings, Comet 41P's nucleus is only 0.6 miles (1 km) in diameter. This makes it highly susceptible to rotational forces. When Comet 41P approached the Sun, the Sun's warmth caused frozen ices to sublimate. This caused unbalanced gas jets that behaved like mini-thrusters. NASA's Swift Observatory detected that Comet 41P's spin slowed down three times over in May 2017. Hubble images taken in December revealed that it now rotates every 14 hours in reverse. Jewitt likened this to pushing a spinning merry-go-round in the opposite direction until it stops and reverses.

A Comet on Borrowed Time

Such a spin reversal could lead to the destruction of comet 41P. As it spins faster, centrifugal forces could overcome the weak gravity binding it together, causing it to come apart. The comet's activity has also decreased tenfold since it passed perihelion in 2001. The near-surface volatile ice is likely depleted or buried under dust. Having been in its current orbit for approximately 1,500 years, comet 41P is in its final stages. According to Jewitt, it will "very quickly self-destruct." The fact that it is an ancient relic in our solar system makes it all the more poignant.