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There’s a pretty endearing idea put forward in Douglas Adams’ sci-fi classic The Hitchhiker’s Guide to the Galaxy, and it’s this: maybe the universe is full of life, aliens hanging around and stopping at intergalactic cafes. And they are all waiting for Earth to stop being the remote tribe of the universe and finally join them.
Could there be some truth to that? There is certainly a lot more going on out there than most Earthlings realize. For example, when you might think you know exactly how many moons each have in our solar system… chances are you’d be very wrong.
Because, spinning out there, in sync with our various neighboring planets, there are still mysterious bodies called quasi-moons that are not exactly satellites, but they are so close to being one that it cannot be said that they are not.
There is a quasi-moon called 2002 VE68 that has been orbiting Venus, for example, for about 7,000 years. It was discovered by Brian Skiff, a researcher at Lowell Observatory in Arizona, in 2002. “It was identified as part of a large study that Lowell Observatory conducted between 1998 and 2010 to find new near-Earth objects. This was one of many objects found during the study and it didn’t seem special at the time,” says Skiff.
In fact, it was mistaken for an asteroid.
Then, in 2004, an international team of astronomers led by Finnish astronomer Seppo Mikkola discovered that 2002 VE68 was not simply an asteroid orbiting the Sun. It was in a sort of dance with Venus, taking the same amount of time to travel around it. of the sun than that planet, in a kind of distant orbit, circling by its side, much further away than a moon would, but still influenced by the planet.
And so Venus, thought to have no moon, turns out to not be so alone after all.
Several quasi-moons have been identified since the first one in 2002. They are not considered real moons, partly because of the weak gravitational link to their planet, and partly because they tend to escape that link and eventually go out of orbit. And also because they treat the Sun as their main partner, not the planet.
The Earth currently has seven quasi-moons. Most are quite small. The 2023 FW13, discovered in 2023, for example, is about the size of three large SUVs combined. Another, 469219 Kamoʻoalewa, is believed to be a ferris wheel-sized chunk of the moon, according to a study published in Communications Earth & Environment in 2021. It has a silicate-based composition, “with redness beyond what would normally occur.” It is seen between the eyes.” asteroids in the inner solar system. The closest match to the object’s physical characteristics was “lunar-type silicates,” the study stated.
Could some quasi-moons be fragments of a planet’s moon? The working theory is that they could, like asteroids, be fragments of any type of ancient space debris, Skiff says.
Researchers are now studying how they move. It is estimated, for example, that 2002 VE68 was once a near-Earth object, before Earth flung it toward Venus. It is expected to remain in its current orbit for another 500 years. After that, it’s unclear where it might be headed.
“We think most nearmoons originate in the inner part of the main asteroid belt between Mars and Jupiter, and are probably thrown into orbits that cross planets after collisions between those bodies,” Skiff says.
It’s a real nightclub in the sky, says Los Angeles-based writer and researcher Latif Nasser in an episode of his Radiolab podcast (and host of Netflix’s Connected). Click here to see how he sparked a viral discussion about quasi-moons online and why he campaigned to rename one of them because of a typo.