The Earth has always had a silent companion in the vast space: the moon. But what if she wasn’t the only one? A recent study published in Nature Astronomy revealed that there is another celestial body that has captured the attention of scientists: the asteroid 469219 Kamo’oalewa. This small asteroid, which orbits in sync with Earth, may have a history surprisingly linked to our beloved Moon.
What is 469219 Kamo’oalewa, the “second Moon” of the Earth
469219 Kamo’oalewa is an asteroid that has attracted the interest of scientists due to its strange relationship with Earth. It was discovered in 2016 by the Haleakalā Observatory in Hawaii, and is a small celestial body with a diameter of about 30-60 meters.
It makes a complete rotation every 28 minutes and sometimes comes as close as 16 million kilometers to Earth due to its orbital path. Scientists call it a “quasi-satellite” of Earth, an object that follows an orbit similar to that of a planet but is not a true satellite.
The origin of the quasi-satellite revealed: what was discovered
According to the study, Kamo’oalewa may come from an impact on the moon which created the Giordano Bruno crater. This crater, 22 km wide and located on the far side of the Moon, has characteristics similar to those of the asteroid: the reflected light, size, age and rotation speed coincide with those of the lunar crater.
Scientists carefully analyzed the light reflected by Kamo’oalewa and compared it with that of lunar samples brought to Earth by space missions. The similarities were striking, suggesting that the asteroid might come directly from the Moon.
The researchers calculated that the asteroid might have been ejected from the Moon after being hit by a space rock about 1.6 km in diameter. It then traveled into space before settling into a near-Earth-synchronous orbit. This scenario offers a plausible explanation for Kamo’oalewa’s presence and its close orbit around our planet.
What is a quasi-satellite and what are terrestrial ones
A quasi-satellite it is a celestial object similar to a planet or satellite, orbiting around the planet itself and its star.
These bodies are in orbital resonance 1:1 with the planet, remaining close for prolonged but variable periods. Their orbits, outside the Hill sphere, are unstable and tend to evolve into other forms of resonance over time.
The orbit of a quasi-satellite around the Sun takes the same time as the planet’s orbit but usually has greater eccentricity. From the planet’s perspective, it appears to circle, even though it doesn’t technically orbit it.
Other types of orbits in 1:1 resonances include horseshoe-shaped ones around Lagrange points, but these objects do not remain near the planet for long. They can periodically transit quasi-satellite orbits for short periods, merging with them. An example is 2002 AA29.
Between known quasi-satellites of Earth there are: 3753 Cruithne, 2002 AA29, 2003 YN107, 2004 GU9, (419624) 2010 SO16, 2014 OL339, 469219 Kamoʻoalewa, 2022 YG and 2023 FW13.
