How Many Moons Does Earth Have?
QUICK ANSWER
Earth has one official moon, the Moon (also called Luna in some scientific contexts). Earth also occasionally captures small asteroids as temporary minimoons that orbit for a few months or years before drifting away, and several quasi-moons travel alongside Earth in shared orbits around the Sun.
Earth has one moon. That's the simple answer. The more complete answer involves footnotes about minimoons, quasi-moons, and other temporary companions that briefly orbit Earth before going their own way. Officially, the count is one. Unofficially, it's complicated.
What is Earth's actual moon?
Earth has one natural permanent moon, called the Moon (or Luna in scientific contexts). According to NASA, the Moon is about 2,159 miles in diameter (roughly a quarter of Earth's size) and orbits Earth at an average distance of about 238,855 miles. It formed about 4.5 billion years ago, probably from debris left over from a massive impact when a Mars-sized object collided with the early Earth. It's the fifth-largest moon in our solar system.
What are minimoons?
Minimoons are small asteroids that get temporarily captured by Earth's gravity and orbit for a short period before drifting back into solar orbit. The first confirmed minimoon was 2006 RH120, which orbited Earth for about a year between 2006 and 2007. Another, 2020 CD3, was captured around 2018 and stayed until 2020. Both were only a few meters across. Scientists estimate Earth probably has a minimoon at any given time, but they're so small (typically 1 to 6 feet across) that they're rarely detected.
What are quasi-moons?
Quasi-moons (or quasi-satellites) are asteroids that share Earth's orbit around the Sun in a way that makes them appear to orbit Earth from our perspective, even though they're really orbiting the Sun in a synchronized pattern. The most famous example is Kamoʻoalewa, a small asteroid discovered in 2016 that loops around Earth on a complex path. Quasi-moons aren't gravitationally bound to Earth, so they're not true moons, but they do travel as companions for thousands of years before drifting away.
Has Earth ever had more than one moon?
Possibly, billions of years ago. Some theories suggest the giant impact that created our Moon may have produced multiple smaller moons that eventually merged with the main Moon or fell back to Earth. There's no direct evidence of these smaller objects, but the computer models work. More recently, there's also speculation that Earth occasionally captures larger objects (like comets or large asteroids) for longer periods, but no large permanent second moon has been documented in Earth's recent history.
Earth has one moon, with a few asterisks. Officially, the count is one big permanent satellite. Unofficially, Earth picks up the occasional temporary minimoon and has quasi-moon companions that loop along its orbit for centuries before moving on. Even the moon count, simple as it looks, has some genuine complexity if you dig into it.
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