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Second Trojan asteroid confirmed to be leading our planet around the Sun

Good candidate for fly-by, say scientists, and we’ve got 4,000 years to do it

Scientists have confirmed the discovery of Earth's second Trojan asteroid leading the planet in its orbit around its nearest star.

Dubbed 2020 XL5, the hunk of space rock was discovered in December 2020. Although excitement surrounded the early observations of a second Earth Trojan, low observational coverage meant uncertainties in the data were too great for a scientific confirmation.

Trojan asteroids are small bodies sharing an orbit with a planet, which remain in a stable orbit approximately 60 degrees ahead of or behind the main body.

Venus, Mars, Jupiter, Uranus, and Neptune all have them but it wasn't until 2011 that asteroid 2010 TK7 was found to be the first Earth could lay claim to. Now a second was confirmed this week.

Around 1.18km across (give or take 80m), 2020 XL5 is probably made of carbon and is the larger of the Earth's Trojan asteroids to be discovered, according to the study published in Nature Communications. Both lead our planet in its trajectory around the Sun.

Toni Santana-Ros, postdoctoral researcher at Barcelona University's Institut de Ciències del Cosmos and his team used archival data from Catalina Sky Survey which revealed promising data from Mount Lemmon telescope in Arizona and the online repository of images from Víctor M. Blanco Telescope, Chile. They combined this data with optical images of 2020 XL5 from 4m class telescopes, the Southern Astrophysical Research telescope in Chile and the Lowell Discovery Telescope in Arizona.

They also made new observations using the European Space Agency's Optical Ground Station 1m telescope on Tenerife, Spain, watching the skies from February 9 last year until March 16. The integration of the orbit data employed ESA AstOD orbit determination software.

As well as confirming the finding, their study shows the Earth Trojan's orbit is likely to remain stable for at least 4,000 years.

They suggest the object may have been thrown out of the Solar System's main asteroid belt following an interaction with Jupiter, but more work is needed to confirm the idea.

Because it is bigger than its sibling, the newly confirmed space rock may be a better candidate for a future fly-by mission, the researchers suggested. ®

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