Our moon may someday become a small planet, say researchers — a 'ploonet'

She may not be ours forever.

Our moon may someday become a small planet, say researchers — a 'ploonet'
Photo credit: Tom White / Getty Images
  • A new study suggests that the moons of gas-giant exoplanets may break away into their own orbits, called "ploonets."
  • Planet + moon = ploonet.
  • As the gas giants move inward toward their suns, the orbits of their moons are often disrupted, according to new computer models.

While exoplanets appear to be plentiful outside our solar system, the moons that we might expect to be orbiting them are another story. Indeed, last spring it looked like astronomers had finally found one — it was dubbed Neptmoon because of its great size — but that finding now appears less certain.

In light of this quandary, a new paper, published on June 27, looks at what might be happening to "exomoons" that orbit large gas-giant planets migrating inward toward their stars, such as our own Jupiter seems to have done.

The researchers — astrophysicist Mario Sucerquia and colleagues — hypothesize that these satellites break free of their tidal connection to their "parent" planets as they move nearer to their sun. The paper suggests that, at this point, they're not quite moons anymore — or planets — but "ploonets."

What's more, our own moon, the researchers say, may meet a similar fate one day, even though Earth isn't a gas giant. Warns Sucerquia:

"Earth's tidal strength is gradually pushing the moon away from us at a rate of about 3 centimeters a year. Therefore, the moon is indeed a potential ploonet once it reaches an unstable orbit."

Image source: JPL/BigThink

The research in the new paper is grounded on the manner in which large gas giants have been observed to slowly move inward through their solar systems toward their respective suns. It suggests that, as such a body draws close to the star, its moon's orbit — affected at that juncture by both the gravitational pull of the planet and the host star — experiences an increase in energy, which becomes unstable. This, eventually, releases the moon from the gravitational bonds of its parent parent.

Further, the paper's conclusions are based on a series of computer simulations that researchers conducted regarding what would happen to a moon orbiting a migrating gas giant. What was discovered?

The models found that 44 percent of the moons would meet their demise by being pulled into their planets (this could explain some of the planetary rings that have been observed). The system's star would seize and destroy another 6 percent. Significant amount of exomoons, however, — about 48 percent of them — would split off from their planets and begin orbiting their star as "ploonets." Around 2 percent would be blown out of their solar system altogether.

This would certainly explain why we haven't definitively found any evidence of exomoons yet.

3,000-pound Triceratops skull unearthed in South Dakota

"You dream about these kinds of moments when you're a kid," said lead paleontologist David Schmidt.

Excavation of a triceratops skull in South Dakota.

Credit: David Schmidt / Westminster College
Surprising Science
  • The triceratops skull was first discovered in 2019, but was excavated over the summer of 2020.
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Credit: gonin via Adobe Stock
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  • Today, we discuss the origin of the quark-gluon plasma and the properties of the famous Higgs boson, the "God Particle."
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Though gloomy and dense, Russian literature is hauntingly beautiful, offering a relentlessly persistent inquiry into the human experience.

Credit: George Cerny via Unsplash
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  • Russian literature has a knack for precisely capturing and describing the human condition.
  • Fyodor Dostoevsky, Leo Tolstoy, and Aleksandr Solzhenitsyn are among the greatest writers who ever lived.
  • If you want to be a wiser person, spend time with the great Russian novelists.
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