Second (and Largest) Earth Trojan Asteroid Found

A new paper details the discovery and confirmation of the second and largest Earth Trojan asteroid to date, 2020 XL5, about 1.2 kilometers in diameter.

IMAGE: Using the 4.1-meter SOAR (Southern Astrophysical Research) Telescope on Cerro Pachón in Chile, astronomers have confirmed that an asteroid discovered in 2020 by the Pan-STARRS1 survey, called 2020 XL5, is an Earth Trojan (an Earth companion following the same path around the Sun as Earth does) and revealed that it is much larger than the only other Earth Trojan known. In this illustration, the asteroid is shown in the foreground in the lower left. The two bright points above it on the far left are Earth (right) and the Moon (left). The Sun appears on the right. CREDIT: NOIRLab/NSF/AURA/J. da Silva/Spaceengine; Acknowledgment: M. Zamani (NSF’s NOIRLab)

One of the latest missions we have been covering has been the Lucy mission to Jupiter’s Trojan asteroids — those asteroids that orbit about 60 degrees in front of and behind the gas giant. Jupiter, it turns out, is not the only planet with Trojan asteroids. Mars, Neptune, and Uranus all have Trojans as well, although not nearly as many as Jupiter. And Earth, up until this week, was known to have one Trojan. But now, NOIRLab has announced the discovery of a second, larger Earth Trojan.

In a new paper published in Nature Communications, scientists detail the discovery of 2020 XL5 which was confirmed using the Southern Astrophysical Research (SOAR) telescope in Chile. The asteroid was originally found with the Pan-STARRS1 survey telescope in Hawai’i back in December 2020. It’s about 1.2 kilometers in diameter, which makes it three times wider than Earth’s other known Trojan asteroid, 2010 TK7.

The team not only observed 2020 XL5 with the SOAR telescope but went back and looked through precovery data from the Dark Energy Survey to put together nearly ten years of…