An article recently caught my attention, and it has reemerged several times now. It is about the idea that Earth has multiple moons. Another version of the story suggests multiple quasi-moons. Great click bait, but what does it all mean? It kind of depends on who you ask.
For purposes of this discussion, let’s refine the term as a large object that orbits a planet. Okay, that is interesting, we have millions of satellites and space junk orbiting our planet, so are they all moons? Let’s add to our definition that it needs to be naturally occurring. Within our solar system, all classified moons are rocky. We do have planets that are mainly gas giants such as Jupiter, but defined moons in our solar system are all rocky. What about size? Let’s see, the smallest classified moon in our solar system at this moment is Deimos. It is roughly seven miles in diameter. There are some objects now being referred to as shepherd moons in Saturn’s belt that may be classified as moons that are even smaller.
When I think of a moon I start with Earth’s moon. The moon is 2,159 miles in diameter. By comparison, Pluto (no longer classified a planet) is about 1,476 miles. Mercury, which is classified as a planet is 3,031 miles in diameter. So, the Moon is pretty close in size to be categorized as a planet. But it is not because it is locked into orbit around a planet… Earth.
Let’s get back to the quasi-moons of Earth. Quasi-moons can rotate around a planet. We have seven identified quasi-moons that have elliptical orbits around the Earth. The largest of the quasi-moons that has been identified is Kamo’oalewa or 2016 HO3. It could be as large as 328 feet in diameter and has a fairly stable orbit. Another quais-moon that was recently discovered is 2023 FW13, about the same size as Kamo’oalewa.
What is the difference between an asteroid and a quasi-moon. That’s probably the better question as these large rocks really are nothing unusual when considering asteroids. The main difference is that they orbit around the Earth as we both orbit around the Sun. Some of these quasi-moons will stick around for thousands of years, others will wander off if another gravitational source disrupts our partnership.
For me, the question now is the storyline for another good science fiction story. One is rattling around in the back of my mind. I just can’t make up my mind if it’s a novel or a short story.