The question “how many moons does Earth have” seems simple at first glance — the instinctive answer is “one.” For centuries, we’ve gazed at our bright, silvery Moon and regarded it as our planet’s lone companion in the night sky. But modern astronomy tells a more fascinating story.
While Earth does indeed have one permanent natural satellite, scientists have discovered that our planet occasionally captures temporary moons, also known as mini-moons or quasi-satellites. These small celestial visitors orbit Earth for short periods before drifting away into the vastness of space.
As of 2025, astronomers continue to study these transient moons, revealing that our planet’s gravitational influence extends much farther — and interacts with far more objects — than once believed.
The Main Moon: Earth’s Timeless Companion
Earth’s primary Moon is our most visible and enduring satellite — a stabilizing force that has shaped the planet’s evolution for billions of years. Formed roughly 4.5 billion years ago, the Moon likely originated from a cataclysmic collision between early Earth and a Mars-sized body named Theia.
Key Facts About Earth’s Moon
- Diameter: 2,159 miles (3,474 km)
- Average Distance from Earth: 238,855 miles (384,400 km)
- Orbital Period: 27.3 days
- Surface Temperature: -280°F to +260°F (-173°C to 127°C)
- Composition: Rock, dust, and small amounts of ice
This single, massive Moon influences everything from our tides to the length of Earth’s day. Its gravitational pull stabilizes Earth’s tilt, which keeps our climate relatively stable — a crucial factor in making the planet habitable.
But Earth’s gravitational field doesn’t just interact with one object. It occasionally traps smaller bodies, turning them into temporary moons for short periods of time.
Mini-Moons: Earth’s Temporary Guests
So, how many moons does Earth have right now? Officially, just one permanent one — but temporarily, sometimes two or three.
Astronomers have confirmed that Earth periodically captures tiny asteroids that orbit our planet for a few months or years before being ejected by gravitational forces. These are called mini-moons or temporarily captured orbiters (TCOs).
These objects are small — often no bigger than a car — and their faint brightness makes them hard to detect. Still, technological advancements in sky surveys and space telescopes have made it possible to spot them when they appear.
The Discovery of Earth’s First Mini-Moon
The first confirmed mini-moon, 2006 RH120, was discovered in September 2006 by astronomers with the Catalina Sky Survey in Arizona.
Here’s what made it fascinating:
- It measured only about 10 feet (3 meters) across.
- It orbited Earth for approximately 11 months (until June 2007).
- After completing four orbits, it escaped Earth’s gravity and resumed orbiting the Sun.
The discovery was groundbreaking. Until then, astronomers had only theorized that small bodies could temporarily orbit Earth. The finding proved that our planet can “borrow” asteroids from the solar system for a short time.
A New Visitor: Mini-Moon 2020 CD3
In February 2020, researchers spotted another mini-moon: 2020 CD3, a small asteroid about the size of a compact car.
- Size: Estimated between 3 and 11 feet wide.
- Captured by Earth: Around 2018.
- Discovered: February 15, 2020.
- Left Earth’s orbit: Around May 2021.
- Discovered by: Catalina Sky Survey, again in Arizona.
Unlike most asteroids, which pass by Earth at high speeds, 2020 CD3 was traveling slowly enough that our planet’s gravity managed to pull it into orbit. It made a few laps around Earth before sunlight and the Moon’s influence nudged it back into space.
NASA described it as a “rare cosmic catch,” demonstrating how Earth’s gravitational field constantly interacts with small space rocks in its vicinity.
How Mini-Moons Form and Leave
Mini-moons are created when small near-Earth asteroids — usually measuring less than 10 meters across — get caught in Earth’s gravity during their journey around the Sun.
For a mini-moon to form, several conditions must align perfectly:
- The asteroid must be traveling slowly enough relative to Earth.
- It must approach Earth at a precise angle to be “snagged” by our gravity.
- Its orbit must avoid immediate collision with either the Moon or the atmosphere.
However, the capture never lasts forever. The combined gravitational forces of Earth, the Moon, and the Sun eventually push the object back into solar orbit.
Are Mini-Moons Dangerous to Earth?
No — mini-moons pose no threat to our planet. They are far too small to cause damage and would burn up as harmless meteors if they entered Earth’s atmosphere.
In fact, scientists see them as opportunities rather than risks. Studying mini-moons helps researchers learn about near-Earth asteroids and test spacecraft navigation systems for future planetary defense missions.
NASA has considered targeting future mini-moons with robotic missions to study their surface composition and dynamics. These small bodies offer a natural laboratory for understanding asteroid behavior close to home.
Quasi-Moons: Earth’s Long-Term Neighbors
In addition to mini-moons, Earth also has quasi-moons — celestial bodies that share a similar orbit around the Sun but are gravitationally linked to Earth.
They’re not true moons because they orbit the Sun rather than Earth directly, but their motion makes it appear as if they’re following us through space.
Kamoʻoalewa (2016 HO3): Earth’s Quasi-Companion
The most famous quasi-moon is Kamoʻoalewa, discovered in 2016 by the Pan-STARRS telescope in Hawaii. Its name, derived from Hawaiian, means “the oscillating fragment.”
Key Facts About Kamoʻoalewa:
- Estimated size: 165–330 feet wide.
- Distance from Earth: Around 9 million miles (14.5 million km).
- Orbital pattern: Orbits the Sun but remains near Earth’s orbit.
- Duration: Has likely followed Earth for centuries and may continue for hundreds more years.
NASA scientists have observed that Kamoʻoalewa’s reflectivity is strikingly similar to lunar rocks brought back by Apollo astronauts, suggesting it may actually be a fragment from our own Moon, knocked into space by an ancient impact.
Other Quasi-Moons
Besides Kamoʻoalewa, a few other quasi-moons have been identified:
- 3753 Cruithne: Discovered in 1986; follows a horseshoe-shaped orbit around Earth.
- 2020 XL5: Detected in 2021; shares Earth’s orbit as a co-orbital asteroid.
- 469219 Kamoʻoalewa: The most stable quasi-moon currently known.
These objects highlight how dynamic Earth’s orbital environment really is.
Could Earth Ever Have Two Permanent Moons?
It’s an exciting idea — but astronomically improbable.
For Earth to permanently capture a second large moon, the object would have to slow down enough to be locked in orbit indefinitely without being ejected by the gravitational influence of our current Moon or the Sun.
Current physics and orbital mechanics make this nearly impossible. The delicate balance between Earth, its Moon, and the Sun’s gravity leaves no room for another stable satellite of significant size.
So, for now, our big Moon remains our one and only permanent companion — but the mini-moons and quasi-moons remind us that the solar system is always in motion.
Why This Question Still Matters in 2025
As of today, scientists continue to refine their models of Earth’s gravitational influence, tracking near-Earth objects with unprecedented precision.
Projects like NASA’s NEO Surveyor Mission, launching later this decade, aim to catalog and study all small bodies passing near Earth’s orbit. This could lead to the discovery of even more temporary moons.
These efforts aren’t just academic — they play a vital role in planetary defense, asteroid mining research, and understanding the early history of our solar system.
Mini-moons may seem small, but they hold clues to how Earth formed and how it continues to interact with its cosmic neighborhood.
So, How Many Moons Does Earth Have?
To summarize:
- Permanent Moon: 1 (our familiar Moon).
- Mini-Moons: Occasionally 1 or 2, temporary in nature.
- Quasi-Moons: Several small co-orbital companions that follow Earth’s path around the Sun.
So, while textbooks are correct in saying Earth has one “true” Moon, the reality is more nuanced. At any given moment, Earth may host a handful of small companions — fleeting guests in our gravitational field.
Final Thoughts
The next time you look up at the Moon, remember that our planet’s story doesn’t end there. Hidden in the vast darkness are other small travelers — temporary moons and co-orbital companions that briefly join Earth on its cosmic journey.
They may not shine as brightly as our main Moon, but they remind us that Earth’s place in space is dynamic, interconnected, and alive with motion.
So yes — Earth has one true Moon, but sometimes, it has company.
Would you like to see NASA send a mission to explore a mini-moon? Let’s hear your thoughts below.