Saturn’s first Trojan asteroid has finally been discovered

Saturn joins the sun’s other giant planets that have Trojans, space rocks that orbit along the same path.

Oct 12, 2024 - 02:30

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Saturn’s first Trojan asteroid has finally been discovered

All four giant planets now have known asteroids sharing their orbits

This image shows Saturn, ringed and in tones of tan, against an inky background. Three tiny light spots at some point of the background and one dot against the lower half of of the planet are four of Saturn's moons.

Saturn is famous for its stunning rings and its many moons (four seen here), but they aren’t the planet’s best companions. Its first known Trojan — an asteroid that shares the planet’s orbit around the sun — has now been revealed.

USGS/JPL/NASA

Astronomers have eventually found an asteroid keeping % with Saturn in its orbit around the sun. Such objects, often often called Trojan asteroids, are already known for the opposite three giant planets.

“Saturn became sort of the odd man out, if I will call it that, because though it’s the 2nd most massive planet at some point of the solar system, it didn’t have any Trojans,” says Paul Wiegert, an astronomer at the University of Western Ontario in London, Canada. Like Saturn, the emblem new asteroid takes about 30 years to revolve but lies 60 degrees beforehand of the planet in its orbit, Wiegert and colleagues report in work submitted September 29 to arXiv.org.

Most asteroids at some point of the solar system revolve around the sun between the paths of Mars and Jupiter. In 1906, alternatively, German astronomer Max Wolf revealed the primary Trojan, which he named Achilles, orbiting the sun 60 degrees beforehand of Jupiter. Since then, astronomers have found thousands of additional Trojan asteroids — some are 60 degrees beforehand of Jupiter, others are 60 degrees at the back of. The NASA spacecraft Lucy will consult with eight of them between 2027 and 2033 (SN: 10/15/21) .

Trojan asteroids also exist for Uranus and Neptune and even for Earth and Mars (SN: 2/1/22).

After a telescope image in Hawaii captured the emblem new asteroid in 2019, an amateur astronomer in Australia, Andrew Walker, suggested that the object is likely to be a Saturnian Trojan — if it had among the appropriate orbit around the sun.

“The major to getting crucial orbit for something in our solar system is having an even deal of observations of it through different telescopes over a long time period,” Wiegert says. So astronomer Man-To Hui at Macau University of Science and Technology in China sought for previous images of the asteroid and planned new observations as well. Measurements of the asteroid’s position — from 2015 to 2024 — confirmed its Trojan nature. Named 2019 UO₁₄, the asteroid is better about thirteen kilometers across, the same size as Deimos, the smaller of the two moons of Mars.

Scientists have long predicted Saturnian Trojans, says astronomer Carlos de la Fuente Marcos of Complutense University of Madrid, who became now now not involved with the invention. But all Saturnian Trojans should have unstable orbits, because Saturn has giant planets on either side of it.

“Jupiter appears to be the culprit,” de la Fuente Marcos says. Jupiter’s great gravity gradually pulls on a Saturnian Trojan, making its orbit around the sun a growing collection of more elliptical. The asteroid then wanders so with regards to Jupiter or Uranus that one of those giant planets yanks the small body out of its Trojan orbit.

If truth be told, the researchers estimate the asteroid has been a Trojan for best about 2,000 years and can remain so for best yet another 1,000 years. Ahead of its affair with the ringed planet, the asteroid became almost for sure a centaur, an asteroid moving around the sun many of the orbits of the huge planets (SN: 11/12/77).

The asteroid almost for sure isn’t Saturn’s sole Trojan. “I’m reasonably sure there are more — maybe best some, but this may’t be among the appropriate one,” Wiegert says.