47P/Kushida-Muramatsu, is the fifth body known to have been drawn by Jupiter (pictured) from its orbit around the Sun.
Credit: ESA/NASA
SYDNEY: Jupiter’s gravity captured a comet in the mid-20th century, holding it in orbit as a temporary moon for 12 years.
The comet, named 147P/Kushida-Muramatsu, is the fifth body known to have been pulled by Jupiter from its orbit around the Sun.
The discovery adds to our understanding of how Jupiter interferes with objects from the ‘Hilda group’, which are asteroids and comets with orbits related to Jupiter’s orbit.
Along for the ride
“Our results demonstrate some of the routes taken by cometary bodies through interplanetary space that can allow them either to enter or to escape situations where they are in orbit around the planet Jupiter,” said researcher David Asher, an astronomer at Armagh Observatory in Northern Ireland.
He presented his findings today at the European Planetary Science Congress in Potsdam, Germany.
Comets from the Hilda group have been seen in collision courses with Jupiter for over 15 years. Most fly by without striking the planet or becoming satellites, but there have been some notable exceptions. Some astronomers have speculated that an Earth-sized black scar, which appeared on Jupiter’s surface in July, could have been from a Hilda group comet slamming into the gas giant.
Shoemaker-Levy 9, the first comet found orbiting Jupiter, is thought to have remained trapped by the planet for over 50 years. It was destined for an explosive end, though. The powerful effect of Jupiter’s gravity tore it into 20 fragments – some up to 2 km across – which plunged into the planet in 1994.
New moon in 2086
Asher’s team set out to find out how often Hilda comets became moon-like satellites of Jupiter. They modelled possible paths of 18 comets, searching for those that completed at least one whole orbit of Jupiter.
Hundreds of possible paths were calculated for 147P/Kushida-Muramatsu, based on tracking observations collected over the past nine years. In all cases, between 1949 and 1961 two full revolutions around Jupiter were completed. This 12-year-long journey is the third longest orbit found to date. Strikingly, Kushida-Muramatsu escaped the fate of Shoemaker-Levy 9, and was thrown back into orbit around the Sun.
The researchers have identified a future moon too. Comet 111P/Helin-Roman-Crockett is predicted to complete six laps of Jupiter between 2068 and 2086.
This won’t be the first time this comet has orbited the giant planet – the study also shows that between 1967 and 1985, Comet 111P/Helin-Roman-Crockett was briefly pulled into orbit for a warm-up run.
“It is remarkable that simple Newtonian gravitation can produce such a complicated orbit transformation and in that process potentially shield, and probably to a lesser extent endanger, the Earth from collision with minor Solar System bodies,” commented James Biggs, the director of the Perth Observatory in Western Australia.
Geraint Lewis, an astrophysicist from the University of Sydney, agrees. “Comets, which fall in from large distances, are attracted mainly by the Sun when they are way out, but as they get closer they feel the pulls of the other planets, distorting their orbits," he said. "This paper shows that Jupiter, with the second strongest gravity in the Solar System, can have a big effect.”
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