Astronomers have discovered that Earth has gained a new companion - another "moon" that will remain in its orbit until approximately 2083.
But it's not the only celestial body that's near our planet as we orbit the Sun.
A small asteroid called 2025 PN7 has been traveling almost in sync with Earth for decades.
"Quasimoons are interesting because they don't actually orbit the planet like the Moon orbits the Earth, but are just in our vicinity," explains Dr Jennifer Millard, an astronomer at the Fifth Star Laboratory in Wales.
This asteroid is about 20 meters long.
"It's not huge, it's the size of a small office building."
"We think it's been around for about 60 years and, based on its current orbit, it will be around for about that many more years," Dr Millard told the BBC.
It was discovered by the Pan-STARRS observatory in Hawaii, United States (USA).
The observatory is equipped with telescopes to monitor objects passing near Earth, such as asteroids and comets.
Earth now has a total of eight identified quasi-moons, an unknown number of mini-moons, and possibly two Kordylevsky clouds (clouds of space dust).
But none of them can match our planet's only true satellite - the Moon.
Watch: Amazing view of the Moon captured by a private lunar spacecraft
Quasi-moons
They are called Earth's quasi-moons because, when viewed from Earth, they appear to orbit it, just as the Moon does.
But when you look closer, you see that these are actually asteroids that orbit the Sun along with the Earth.
"As they orbit the Sun, they move through space in a very similar path to the Earth."
"It looks like they're orbiting the Earth because they're staying very close to us."
"Sometimes they go ahead of us, sometimes they go behind us, but they're not actually gravitationally bound to Earth, and that's the key difference," explains Dr Millard.
But as these asteroids follow their orbits, they are also slightly influenced by Earth's gravity, which pulls them closer.
All of Earth's known quasi-moons are temporary - their orbits can last for decades, or even longer than a century.
Mini-months
Unlike a quasi-moon, a minimoon is an object that actually orbits a planet.
Earth's minimoons are small asteroids temporarily held by Earth's gravity - remnants from the formation of the solar system or perhaps other space debris - and usually remain in orbit for less than a year.
They are tiny and difficult to detect.
Only four have been observed so far, and none are now orbiting Earth.
The last mini-moon was observed in August 2024.
The asteroid, known as 2024 PT5, is about 10 meters long.
It is thought to have originated from the Arjuna asteroid belt - a group of space rocks whose orbit is similar to Earth's path around the Sun.
But a more detailed analysis of its chemical composition suggests that 2024 PT5 is actually a piece of the Moon itself, long ago ejected into space after an asteroid impact.
It was only near Earth for a few months, and then returned to the asteroid belt from which it came.
Kordiljevski Clouds or 'Ghost Moons'
The Kordiljevski clouds are the most enigmatic of these three phenomena.
These are believed to be clouds of space dust in Earth's orbit, which remain in front of or behind our planet as it orbits the Sun.
However, there is not yet a broad scientific consensus on whether they actually exist.
Dr. Millard believes that the assumption that they exist is plausible.
"There's a lot of dust in space," she says.
"There are interplanetary dust particles, so it wouldn't surprise me if there was dust trapped by gravitationally stable points around Earth's orbit."
Are quasi-moons and mini-moons dangerous?
Despite their proximity on an astronomical scale, these objects never come close enough to pose any danger.
Even when they are closest to us, they are several times farther away than the Moon.
By space standards, this is considered "close," but in reality there is no reason to worry.
"If they were really approaching us, they would be approaching very slowly, so we would be able to spot them in time and have enough space to react," explains Dr. Millard.
What other planets have quasi-moons?
Only in recent decades have telescopes become sensitive enough to spot these faint, almost elusive asteroids.
Advances in computing have allowed scientists to model their motion and confirm that these mysterious objects are actually quasi-moons.
"They're not uncommon, they're just very difficult to detect," says Dr. Millard.
"If it's so hard to detect them near Earth, can you imagine how hard it would be to find them elsewhere in the solar system?"
So far, quasi-moons have been observed around Jupiter, Venus, Saturn, Neptune, and Pluto, and it is possible that more will be discovered in the future.
"The solar system is still a very active and dynamic place," says Dr. Millard.
"It is not dead or static, everything in it is constantly moving."
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