NASA’s Hubble Telescope observes comet with unprecedented inverted rotation
An artist’s illustration shows comet 41P/Tuttle-Giacobini-Kresák, a Jupiter-type celestial body, approaching the Sun as its frozen gases sublime, releasing material into space. Researchers analyzed images from NASA’s Hubble Space Telescope and found that these jets altered the comet’s rotation, causing it to spin in the opposite direction.
Astronomers operating NASA’s Hubble Space Telescope have found the first evidence that a small comet slowed down and then completely reversed its direction of rotation. This finding offers a clear example of how unpredictable activity can influence the rotation and physical evolution of smaller celestial bodies in the solar system.
The object, called comet 41P, likely formed in the Kuiper Belt and was directed to its current trajectory by Jupiter’s gravitational pull. It currently visits the inner solar system every 5.4 years.
After its closest pass to the Sun in 2017, scientists noticed a drastic slowdown in comet 41P’s rotation. Data from NASA’s Neil Gehrels Swift Observatory, collected in May 2017, indicated that the object was rotating three times slower than recorded in March of the same year, when observed by the Discovery Channel Telescope at Lowell Observatory in Arizona.
A new analysis, based on subsequent Hubble observations, revealed that the comet’s rotation took an even more unexpected course.
Images captured by Hubble in December 2017 showed the comet spinning much faster again, completing a rotation in approximately 14 hours, in contrast to the 46 to 60 hours measured by Swift. The simplest explanation, according to the researchers, is that the comet continued to slow down until it almost stopped and was then driven by jets of gases released on its surface to spin in the opposite direction.
The scientific paper detailing this discovery was recently published in The Astronomical Journal.
Learn more: Rare phenomenon in space causes comet to reverse its direction of rotation after the action of gases
Small and influenceable nucleus
Hubble also allowed us to estimate the size of the comet’s nucleus, which measures about 0.6 miles in diameter, approximately one kilometer, equivalent to about three times the height of the Eiffel Tower.
This size is considered especially small for a comet, which makes it more susceptible to having its rotation altered or reversed.
When a comet approaches the Sun, the intense heat causes the frozen ice on its surface to sublimate, releasing material into space.
“Gas jets expelled from the surface can act as small propellants,” explained David Jewitt, author of the article and researcher at the University of California, Los Angeles. “If these jets are unevenly distributed, they can drastically modify the rotation of a comet, especially a small comet.”
Initially, the comet rotated in a specific direction, but the jets of gas that propelled it against that motion gradually slowed it down. As the jets persisted in their action, they eventually caused the comet to begin rotating in the opposite direction.
More on this story: Hubble data reveals comet that stopped and reversed rotation driven by gas jets
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“It’s like pushing a merry-go-round,” said Jewitt. “If it’s spinning in one direction, and you push it in the opposite direction, you can slow down and reverse the direction of rotation.”
Signs of rapid changes
The study also indicated a significant decrease in the comet’s overall activity since its previous appearances. During its passage through perihelion in 2001, comet 41P exhibited unusual activity for its size. By 2017, its gas production had fallen by approximately an order of magnitude.
This change suggests that the comet’s surface may be in a process of accelerated evolution, possibly due to the depletion of volatile materials near the surface or the formation of insulating layers of dust on it.
On the same topic: Hubble Telescope records reversal in comet’s spin and astronomers debate possible artificial origin
While most transformations in comet structure take centuries or more to occur, the rapid rotational changes observed in comet 41P offer a unique opportunity to observe evolutionary processes on a human timescale.
Modeling based on measured torques and mass loss rates indicates that continued rotational changes may, at some point, lead to structural instability of comet 41P. If a comet spins too quickly, centrifugal forces can overcome its weak gravity and cohesion, potentially causing it to fragment or even disintegrate.
“My prediction is that this core will self-destruct very quickly,” Jewitt said.
Still, Comet 41P is likely to have been in its current orbit for about 1,500 years.
Discovery in data archive
Hubble has been collecting imaging and spectroscopic data from across the cosmos for more than 35 years. All of these observations are available in the Mikulski Archive for Space Telescopes, a data center that stores information from more than a dozen astronomical missions, including Hubble itself.
More on this story: Hubble images show comet 41P reversing rotation in space after intense gas activity
Jewitt made the discovery when browsing the archive and realizing that observations relating to comet 41P had not yet been analyzed by other researchers.
By making NASA science data accessible to everyone, observations made years, or even decades ago, can be revisited to answer new scientific questions. In many cases, scientists continue to make discoveries not only with new observations, but also by exploring the vast archive built over decades of space exploration.
