(NOIRLab/NSF/AURA/J. da Silva/Spaceengine)
Astronomers have finally confirmed the status of asteroid 2020 XL5, discovered in 2020, as the second terrestrial Trojan.
It was captured by the Earth 600 years ago and will be with our planet for another 4,000 years.
Trojan asteroids are a natural population of the vicinity of the Lagrange points L4 and L5 of the Sun-planet systems, where the balance of gravitational and centrifugal forces is stable.
Currently, more than 7 thousand Trojans belonging to Jupiter have been found, Neptune has 28 of them, Mars has 9, and Uranus and Venus have only one each.
Until recently, only one Trojan asteroid 2010 TK7, discovered in 2011, was known near the Earth.
It is dynamically stable for only a quarter of a million years, and therefore, most likely, it could have previously been captured from somewhere as a near-Earth asteroid.
Asteroid 2020 XL5 was discovered by Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) on December 12, 2020.
Further observations of it in 2021 allowed astronomers to assume that they were facing the second known terrestrial Trojan, but there was not enough data for a final decision.
A team of astronomers led by Toni Santana-Ros of the University of Barcelona in Spain said they have confirmed the status of 2020 XL5 as the second terrestrial Trojan asteroid.
The scientists used observational data from various ground-based telescopes between 2012 and 2019 and 2021 to refine the orbit, determine properties and investigate the object's stability at the L4 point of the Sun-Earth system.
Scientists have concluded that 2020 XL5 has not been with the Earth since its formation, but was captured about 600 years ago
The object will be an Earth Trojan for another 4 thousand years, after which it will leave the Earth.
An analysis of the photometric data showed that the asteroid could be of the C type and be a dark body containing a lot of carbon.
Its diameter is estimated at 1.18 kilometers, the absolute magnitude is 18.58, and the albedo is 0.06.
The researchers also determined that both terrestrial Trojans are difficult targets for robotic research vehicles that launch from low-Earth or geostationary transfer orbits.
However, in the case of 2020 XL5, the possibility of research from a flyby trajectory remains.
Source:
Nature Communications: https://www.nature.com/articles/s41467-022-27988-4
Space.com: https://www.space.com/earth-extra-moon-trojan-asteroid-2020-xl5-discovery