The Earth now has another moon to tag along during its orbit around the Sun.
Astronomers found out that the Earth has two moons while using the Pan-STARRS survey at the Haleakala Observatory in Hawaii in August 2024.
The celestial body, dubbed 2025 PN7, is a quasi-satellite that orbits around the Sun, making it look like a second moon.
'Quasi-satellites are in a resonant orbit but are not gravitationally bound to Earth, allowing for more sustained, though unbound, proximity,' the team of astronomers who found the object wrote in the Research Notes of the AAS. 'Here, we present the newest member of this class, 2025 PN7.'
It means that quasi-moons are not actual moons. Instead, the Planetary Society's Asa Stahl labeled them as asteroids.
What Makes Quasi-Moons Different from a Real One?
The quasi-moon is a rare celestial being that seems to orbit the Earth, but it actually orbits around the Sun. It has almost the same orbital period as the planet, which means it goes around the Sun for 365 days.
Yet unlike the natural moon, quasi-moon does not have the same gravitational pull that holds a celestial body in place.
Quasi-moons are independent celestial bodies that are only loosely bound by Earth's gravity. This fragile gravitational link can last for decades or even centuries before the object eventually breaks free and drifts away.
What Does 2025 PN7 Look Like?
The newly discovered celestial object is very small, with an estimated size of about 18-36 metres across. It has a height similar to a simple building.
This is not the first time for the Earth to have a younger companion. Archival images shared that it may have orbited the Earth for decades, or even centuries.
It could be the 'smallest and least stable' among all seven quasi-moons discovered on Earth, according to astronomer Carlos de la Fuente Marcos in an interview with Live Science.
The 2025 PN7 could not orbit the Earth directly. 'Quasi-satellites are especially interesting, because their cycling around Earth allows even very small asteroids like this one to be studied for years, and often decades, as they repeatedly come back to visit us,' another astronomer explained in an article from Sky & Telescope.
Why was 2025 PN7 Only Discovered Now?
If the new quasi-moon has been around for decades, astronomers only noticed it recently because of its size. The estimated measurement of this celestial object made it impossible to see using amateur telescopes.
Also, the latest telescope models can only spot the quasi-moon when it's closer to the Earth.
Another astronomer also explained the challenges of spotting a quasi-moon, saying: 'based on what little we know so far, it's almost certainly a rocky and natural object—sometimes old satellites and rocket junk end up in these very-near-Earth kinds of orbits, but we can often tell 'natural' (e.g., asteroidal) from 'artificial' (e.g., satellite) based on how their orbits evolve on short timescales.'
NASA reportedly estimated that the quasi-moon will orbit with the Earth until around 2083, but the experts cannot provide an exact timeline for these smaller celestial items until it detaches itself from the planet's gravity.
Originally published on IBTimes UK
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