Some of the fast radio burst could be the result of exploding planets. Credit: DepositPhotos

Are There “Captured Planets” Hiding in the Oort Cloud?

Astronomers propose the existence of "captured" planets hiding in the Oort Cloud.


The trajectory of our solar system reveals a tumultuous past. While today’s planets have settled into stable orbits, they’ve endured significant location shifts during their formation. Jupiter, for instance, once sat much closer to the sun, inciting shifts in other planets and clearing the solar system of debris, much of which ended up in the Oort Cloud.

The Oort Cloud, located at our solar system’s gravitational fringe, occasionally nudges a piece of icy matter into the inner solar system, forming comets. Amidst the Oort Cloud debris, potentially planet-sized entities may be hidden, perhaps even more distant than the speculated Planet X.

“Captured Planets” Hiding in the Oort Cloud?

Some debris flung from the inner solar system may have been propelled even further, escaping the sun’s gravity and drifting in interstellar space. This is evident from our interstellar cometary visitors, Oumuamua and Borisov, in 2017 and 2019 respectively. Furthermore, we’ve detected rogue planets that have severed the gravitational bonds of their native star, suggesting a plethora of celestial orphans scattered throughout the galaxy.

An intriguing question arises: Can young planetary systems shed comets and planets, and could these celestial bodies be caught by other star systems? A paper published in the Monthly Notices of the Royal Astronomy Society delves into this possibility.


Simulating the Celestial Dance

The researchers examined the mechanisms of planetary system ejection and potential captures through a series of computer simulations. The complex gravitational dynamics suggest that a planet requires ample kinetic energy to escape its star, making it difficult for another star system to retain it.

However, the researchers discovered that the galaxy’s gravitational pull could slow a rogue planet’s motion. Hence, a small percentage of celestial encounters might result in a star capturing a planet as a new addition to its family. The most likely location for this capture is within the outskirts of the star’s system, just within its Oort cloud.

Calculating the Odds of Captured Planets in the Oort Cloud

The study suggests that up to 10% of a star’s original planets could be expelled into deep space. Factoring in galaxy dynamics and the early solar system, there’s roughly a 7% chance that our solar system harbors a captured ice giant planet in the Oort Cloud – higher than the odds of an ice giant forming in the solar system and being pushed out.


Hence, if there’s a planet at our solar system’s edge, it’s more likely an adopted entity than a native one. While the absence of large worlds in the Oort Cloud is still most probable, the study underscores the interconnectedness of planetary systems and the potential for star systems as blended families.

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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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