Scientists from Princeton University have proposed that a hidden collection of worlds may orbit beyond Pluto. Their work suggests there could be a planet larger than Mars hiding in the distant outskirts of the solar system, along with three bodies roughly Mars-sized and as many as five objects with masses similar to Mercury. The researchers report their preliminary findings in a paper published in Astrophysical Journal Letters.
The outer reaches of the solar system are so far from the Sun that direct observations are challenging. Telescopes struggle to capture clear images, and researchers increasingly rely on indirect methods to infer what lies beyond Neptune and the Kuiper Belt. Some theorists even speculate that planets originating from other star systems drift through interstellar space and occasionally wander into our solar neighborhood.
These rogue or free-floating planets are not bound to a sun. They drift through the galaxy, sometimes passing close to another star, where gravity can capture them and even merge with the local system. At present, the frequency of such events remains uncertain, and their overall population in the Milky Way continues to be a topic of active research.
The team behind the study attempted to estimate how many of these wandering planets might exist in the Milky Way and what fraction of stars could gravitationally attract them. The calculations indicate a meaningful odds that a planet could traverse the cold, dark space between the most distant rocky worlds and the inner planets, potentially becoming part of a new star system under the right conditions.
The authors emphasize that future work should add more detailed simulations. These would explore how captured planets are retained over time and where they are likely to settle in a host system’s layout. Additional observational tests are also proposed to help confirm the presence of captured planets and to clarify their signatures in the sky.
Earlier studies have sometimes suggested a different picture of Mars’ activity, yet ongoing observations continue to refine our understanding of the Red Planet’s geology and climate. The evolving view underscores that planetary science is a dynamic field where new data can revise long-standing ideas.