second asteriod
Earth has a second 'Trojan asteroid' trapped in the same orbit as us
Earth's second 'Trojan asteroid' — a space rock that shares the same orbit around the sun as a planet — has been discovered by astronomers.
Prior to the detection of Earth's first Trojan asteroid in 2010, the space rocks had only been spotted at Jupiter, Neptune and Mars.
This second example, named 2020 XL5, will remain trapped in the same orbit as Earth for at least 4,000 years, according to an international team of researchers.
Trojan asteroids orbit in the same plane as a planet, but don't collide with it because they occur in 'dead zones' where gravitational forces allow the space rock to circle in a 'sweet spot' at precisely the same speed as the planet.
WHAT IS A 'TROJAN ASTEROID' AND WHERE ARE THEY FOUND?
A 'Trojan asteroid' is a type of space rock that shares the same orbit around the sun as a planet.
They had previously only been spotted at Jupiter, Neptune and Mars prior to 2010.
However, the discovery of 2010 TK7 made Earth the fourth planet in the Solar System that is known to share its orbit with an asteroid.
Now, a decade later, the second of Earth's Trojan asteroids has been spotted by an international team of researchers.
The newly-detected 2020 XL5 is 1,800ft-wide and will remain trapped in the same orbit as Earth for at least 4,000 years.
Experts say it is a great candidate for future fly-by missions.
Trojans orbit in the same plane as a planet, but don't collide with it because they occur in 'dead zones' where gravitational forces allow the space rock to circle at precisely the same speed as the planet.
The newly-detected 2020 XL5 is 1,800ft-wide and is a great candidate for future fly-by missions when astronauts eventually go beyond the moon and the International Space Station, experts have said.
It is also highly likely that there are other Trojans waiting to be found not far from Earth.
The asteroids are important because experts hope their peculiar orbits will help shed light on what the early Solar System was like and how it evolved.
Researchers led by the University of Barcelona used ground-based observations to determine that the 2020 XL5 asteroid is most likely composed of carbon, and may have been ejected from the main asteroid belt by Jupiter.
It was originally discovered on December 12, 2020.
Video: A Massive Asteroid Is About to Perform Up-Close Flyby of Earth (The Independent)
Early observations suggested that it might have been an Earth Trojan asteroid, but experts said that because of low observational coverage, orbital uncertainties were too large for confirmation until now.
Toni Santana-Ros, of the University of Barcelona, studied the orbit of 2020 XL5 with colleagues and combined archival data with observations from three ground-based observatories.
Using this analysis, the scientists confirmed 2020 XL5 to be the second identified Earth Trojan asteroid, after 2010 TK7.
They also carried out an orbital stability analysis and believe that 2020 XL5 will remain in its orbit for at least 4,000 years.
The authors said 2020 XL5 was a larger asteroid than 2010 TK7, which will never get closer than 50-times the distance the moon sits from the us, and may be a better candidate for a future fly-by mission.
They wrote in their paper: 'Trojan asteroids are small bodies orbiting around the L4 or L5 Lagrangian points of a Sunplanet system.
'Due to their peculiar orbits, they provide key constraints to the Solar System evolution models.'
The researchers added: 'We confirm that the recently discovered 2020 XL5 is the second transient Earth Trojan known.
'To study its orbit, we used archival data from 2012 to 2019 and observed the object in 2021 from three ground-based observatories.'
They said Trojan asteroids close to Earth 'may become ideal targets for space missions and, in the more distant future, to settle human bases or install scientific hardware that would benefit from their peculiar location'. Asteroid may be with us for 4,000 yrs.
The study has been published in the journal Nature Communications.
Read moreAn asteroid that was discovered riding along in Earth's orbit is about three-quarters of a mile (1.2 km) wide and might remain as a hitchhiker with our planet for at least 4,000 more years while posing no danger, scientists said on Tuesday.
Using observations from telescopes in Chile, Arizona and the Canary Islands, researchers provided the most comprehensive description yet of the asteroid, named 2020 XL5 and first detected two years ago. They confirmed it is one of only two of what are called Trojan asteroids traveling as a companion with Earth.
Trojan asteroids can be wanderers in the solar system - as appears to be the case with this one - or material left over from their home planet's formation. They become ensnared by the planetary gravitational grip and subsequently orbit the sun along the same path as that planet.
This one looks to be a so-called C-type asteroid - one of the most common kinds in the solar system, according to planetary scientist Toni Santana-Ros of the University of Alicante and the University of Barcelona's Institute of Cosmos Sciences in Spain, lead author of the study published in the journal Nature Communications https://www.nature.com/articles/s41467-022-27988-4.
These are dark in color and contain a lot of carbon along with rocks and minerals.
"2020 XL5 poses no threat to Earth. We expect it will remain in its current stable orbit for at least the next 4,000 years," said telescope scientist and study co-author Cesar Briceño of the U.S. National Science Foundation's NOIRLab.
Video: By the Numbers: The massive asteroid that came within 1.2 million miles of Earth (ABC News)
Its location varies between about 56 million miles (90 million km) and 168 million miles (270 million km) from Earth.
The asteroid occupies one of five so-called Lagrange points - positions in space where objects tend to stay put. These five locales allow for stable orbits due to the competing gravitational forces of Earth and the sun. This one resides at what is called the L4 point.
The only other Trojan asteroid seen around Earth, discovered 12 years ago, also at the L4 point, and called 2010 TK7, is smaller, with a diameter of about a quarter mile (400 meters). It, too, is thought to have been captured by Earth's pull while meandering through the solar system.
2020 XL5, first detected in December 2020 using a telescope in Hawaii, may have been captured by Earth's gravitational pull somewhere between 500 to 1,000 years ago, Santana-Ros said.
Numerous Trojan asteroids populate our solar system, with the largest planet Jupiter known to have almost 10,000 of them, Santana-Ros said. NASA launched a spacecraft https://www.reuters.com/lifestyle/science/nasa-launch-first-space-probe-study-jupiters-trojan-asteroids-2021-10-16 called Lucy last October to explore them. Trojan asteroids also have been found around Neptune (28 of them), Mars (four), Uranus (two) and Venus (one).
"Jupiter is a giant in all senses, also in terms of mass. It cleaned its neighboring region of other objects and gathered thousands of objects on its L4 and L5 points," Santana-Ros said. "However, the Earth has a more delicate environment, with close gravitational competitors like Venus, Mars or even the moon. Therefore, gravitational perturbations on 2020 XL5 will eventually allow this object to escape from the L4 stability point."
Santana-Ros said there could be more Trojan asteroids around Earth awaiting detection. The two Lagrange points where they might exist, L4 and L5, are notoriously difficult to observe from Earth.
"Any asteroid orbiting around these points will only be visible during a short time window close to twilight, at very low elevations above the horizon," Santana-Ros added. "But if we point our largest telescopes low above horizon and close to twilight I am certain we will find more surprises."
(Reporting by Will Dunham, Editing by Rosalba O'Brien)
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