Although Saturn was not previously known to have a Trojan, one of its moons, Tethys, has two moons of its own, one of which, Calypso, was imaged by Cassini and likely resembles 2019 UO14.
The Lucy spacecraft was sent to study Jupiter’s Trojan asteroids – bodies that follow the same orbit but at Lagrangian points 60 degrees ahead or behind the giant planet. She goes there because we expect these asteroids to reveal some interesting things about the development of the Solar System, but also because there are so many to explore.
We also know about Trojans when it comes to the other giant planets as well as Earth and Mars. However, until now, Saturn was missing.
Those who believed in the ancient myths might have concluded that Saturn ate the Trojan asteroids, as the Roman god did with his children. However, scientists were convinced that Saturn must have Trojans and continued the hunt until they were rewarded with the discovery of asteroid 2019 UO14.
However, the Trojan status of 2019 UO14 is only temporary. That’s not particularly unusual. Many Trojans are transient. A planet’s gravity slowly changes the orbits of nearby objects until they orbit Lagrange point 4 (L4), 60 degrees ahead of the planet, or L5, 60 degrees behind.
In a single-planet star system, this might be the end of things, but the constant slight gravitational pull from other planets is disruptive, so many Trojans eventually drift far enough away from the Lagrange point and go into orbit non-Trojan.
“2019 UO14 was likely captured as a Centaur and became trapped around L4 about 2,000 years ago,” the researchers write.
The Lucy spacecraft was sent to study Jupiter’s Trojan asteroids
In astronomical terms, Centaurs are objects that orbit between Jupiter and Neptune and cross the orbit of at least one planet. They expect it to have another thousand or so years of Trojan status ahead of it.
If 2019 UO14 has a similar composition to many other Centaurs, sharing Saturn’s orbit would make it hot enough that some of its ice turns to gas and escapes, taking the dust with it. In other words, it would be a comet, as astronomers say.
The observations made show no sign of activity, but the authors believe that the chances are high enough to justify further work. If they are right, this would be the first active Trojan ever observed.
At the distance between Uranus or Neptune and the Sun it is too cold for ice to melt. At Jupiter, some gas would have escaped long ago, while ice, such as water ice, would be stable. If 2019 UO14 is not active, the authors propose that it once orbited closer to the Sun and then lost its more volatile ice.
Centaurs are objects that orbit between Jupiter and Neptune
The lack of previous Trojans for the Saturn is somewhat odd. There are more than 13,000 known Trojans for Jupiter. It’s no surprise that Saturn has fewer – after all, its gravity is lower, it can’t attack a nearby asteroid belt as easily, and those that do exist would be further away from us and therefore harder to be observed.
However, the Trojan status of 2019 UO14 is only temporary. That’s not particularly unusual. Many Trojans are transient.
A planet’s gravity slowly changes the orbits of nearby objects until they orbit Lagrange point 4 (L4), 60 degrees ahead of the planet, or L5, 60 degrees behind. In a single-planet star system, this might be the end of things, but the constant slight gravitational pull from other planets is disruptive, so many Trojans eventually drift far enough away from the Lagrange point and go into orbit non-Trojan, write IFLScience.
The authors conclude that 2019 UO14 was likely captured as a Centaur and became trapped around L4 about 2,000 years ago.
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Source: www.descopera.ro
