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How many moons are in the solar system?




If you look up on a clear night, the brightest and largest object in the sky will probably be the moon. And unless you have a decent telescope, it is the only natural satellite you can see with your own eyes. As a result, most people have a warped perception of what a moon is and how common these natural satellites really are.

In reality, there are hundreds, if not thousands, of natural satellites, in our cosmic neighborhood, ranging from irregular town-size space rocks to massive rounded bodies that are potentially big enough to be considered planets in their own right.

So exactly how many solar system moons have we found? The answer, it turns out, depends on your definition of a moon. 

The International Astronomical Union (IAU) officially recognizes 288 planetary moons orbiting the solar system's eight worlds, according to NASA. But there are also a further 473 "small-body satellites" — the moons of asteroids and dwarf planets — listed by NASA's Jet Propulsion Laboratory. If we count both types, as most astronomers would, this brings the total number of natural solar system satellites to 761 (as of June 2024). 

But this is likely just "the tip of the iceberg," Edward Ashton, an astronomer at the Academia Sinica Institute of Astronomy and Astrophysics in Taiwan, told Live Science in an email. Astronomers have found dozens of new planetary moons and small-body satellites in the last few years alone, and technological advancements will likely accelerate the rate at which they can spot more in the coming years, he added.

What is a moon? 

"The simplest definition [of a moon] would be an object that is in an orbit around a larger, non-stellar object," Ashton told Live Science. "But that is not quite the complete answer." 

For example, there are currently thousands of human-made satellites in orbit around Earth that satisfy the definition above but are not considered moons because they are not natural. These spacecraft also have limited life spans before falling back to Earth and burning up in our atmosphere.