Earth gains a ‘quasi-satellite,’ a new ‘moon’ to linger for millennia

Scientists have made an exciting find—an asteroid that shares Earth’s orbit around the Sun, known as 2023 FW13. This asteroid is being referred to as a “quasi-moon” or “quasi-satellite.”

This classification arises because the asteroid orbits the Sun on a similar cycle to Earth but is also influenced by Earth’s gravitational force. The asteroid, approximately 50 feet (15 meters) wide, orbits at a distance of about nine million miles (14 million kilometers) from Earth.

The discovery was made using the Pan-STARRS survey telescope situated atop Haleakala, a dormant volcano on the island of Maui, Hawaii, on March 28, 2023. Additional observations confirming the asteroid’s presence near Earth were made by the Canada-France-Hawaii telescope and two observatories in Arizona: the Kitt Peak National Observatory and the Mt. Lemmon SkyCenter.

The asteroid was officially cataloged by the Minor Planet Center of the International Astronomical Union on April 1, an organization that also designates new moons, planets, and other celestial bodies in our solar system.

Journalist and astronomer Adrien Coffinet, intrigued by the asteroid, used an orbit simulator developed by amateur astronomer Tony Dunn to analyze its trajectory. The simulation showed that 2023 FW13 travels around the Sun in lockstep with Earth, leading Coffinet to classify it as a “quasi-moon.”

However, Alan Harris, a senior research scientist at the Space Science Institute in Boulder, Colorado, suggests that calling it a “quasi-satellite” might be somewhat of a stretch, given Earth’s significant influence on its orbit.

Researchers estimate that 2023 FW13 has been Earth’s cosmic companion since at least 100 BCE and is projected to continue in this orbital dance until about 3700 CE. Coffinet remarked that this makes it the longest-known quasi-satellite of Earth.

Despite its proximity, scientists reassure that the asteroid’s trajectory is not on a collision course with Earth. Harris noted, “The good news is, such an orbit doesn’t result in an impacting trajectory ‘out of the blue.'”