An asteroid chasing Earth? A new Trojan asteroid was just confirmed

And it won't change course for four thousand years.
Chris Young
An artist's impression of 2020 XL5NOIRLab/NSF/AURA/J. da Silva

An asteroid is hurtling in our direction, though thankfully the small space rock won't actually collide with Earth.

An international team of astronomers confirmed the existence of a second Earth Trojan asteroid, named 2020 XL5, two years after scientists first believed they observed the celestial object.

The team, led by University of Barcelona researcher Toni Santana-Ros, published their findings in the journal Nature Communications. They also outlined potential plans for traveling to 2020 XL5, and any future Trojan asteroids that might be discovered.

Scientists confirmed the existence of a second Trojan Earth asteroid

Trojan asteroids are small space rocks that share their orbit with a planet as both revolve around their host star. Scientists have long known of the existence of Trojan asteroids. In fact, in October last year, NASA launched a mission, called Lucy, to investigate eight Trojan asteroids of Jupiter.

Trojan Earth asteroids have been harder to come by, though, as the space rocks are difficult to observe due to their trajectory around the Sun. The observation time window is typically very small, with the space rocks tending to be observable only shortly before sunrise.

2020 XL5 shares our exact orbit with the Sun, making it the second Trojan Earth asteroid to be discovered — the existence of the first, called 2010 TK7, was confirmed in 2011. The team of researchers who confirmed the existence of 2020 XL5 calculated that the asteroid will likely stay on the same orbital trajectory for four thousand years, meaning it is classified as a transient Trojan Earth asteroid. They also estimated that the asteroid is roughly 0.62 miles (one km) in diameter. As a point of reference, the first Trojan Earth asteroid to be discovered, 2010 TK7, had a 0.18 miles (0.3 km) diameter. 

Traveling to a Trojan asteroid could be easier than reaching the Moon

Though only two have so far been discovered, there may be many Trojan Earth asteroids, and they could provide insight into the very early Solar System. That's because these space rocks may have been orbiting the Sun for as long as Earth and some of its neighboring planets.

An asteroid chasing Earth? A new Trojan asteroid was just confirmed
The diagram above shows Earth-Sun Lagrange points, where small orbiting object are under the influence of the two large celestial objects. Source: NOIRLab/NSF/AURA/J. da Silva

The researchers also pointed out the fact that, due to the fact that Trojan asteroids mirror our orbital trajectory, it would take a low change in velocity to reach these space rocks using a rocket. That means that they could become research centers as well as bases from which to explore the far reaches of the Solar System.

In a statementCesar Briceño, one of the authors of the study, said "if we are able to discover more Earth Trojans, and if some of them can have orbits with lower inclinations, they might become cheaper to reach than our Moon," Briceño said. "So they might become ideal bases for an advanced exploration of the solar system, or they could even be a source of resources." Before that can happen, we will likely have to discover more Trojan Earth asteroids to gain a better understanding of the ancient space rocks sharing our orbital trajectory with the Sun. 

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