Planets near black holes
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Planet Formation Near Supermassive Black Holes
Recent research shows that planets can form around supermassive black holes (SMBHs), especially in the disks of active galactic nuclei (AGNs). In these environments, dust particles can grow and stick together more easily than in typical protoplanetary disks, eventually forming large, Earth-sized planets. The process is helped by low collision speeds and unique disk conditions, allowing planetesimals to form without being stopped by the usual "radial drift barrier." These planets can reach up to ten times the mass of Earth and may form over timescales similar to the active phase of the AGN, especially around lower-mass SMBHs .
Effects of Black Hole Radiation on Nearby Planets
Planets near SMBHs, such as those close to the Milky Way’s central black hole (Sgr A*), are exposed to intense radiation during quasar phases. This radiation can strip away the atmospheres of sub-Neptune-sized planets, leaving behind rocky cores. Many of these stripped planets could end up in the habitable zones of their stars, potentially increasing the number of terrestrial, super-Earth-type planets near galactic centers. The high density of stars in these regions also means that habitable planets are much closer together, which could make the transfer of life (panspermia) between planets more likely .
Primordial and Mini Black Holes in Planetary Systems
Some theories suggest that small, primordial black holes (PBHs) could exist within our solar system or even inside planets. These PBHs could influence planetary orbits, internal heat, and magnetic fields. However, current measurements show that any gravitational effects from PBHs on planetary orbits are too small to detect with present technology. Improved measurement accuracy could make it possible to detect such influences in the future 34.
There is also speculation that the mysterious "Planet Nine" in the outer solar system could be a mini black hole. If so, its presence could be confirmed by observing flares from objects falling into it, and upcoming surveys like LSST may soon provide answers. The existence of such planet-mass black holes could also help explain some dark matter phenomena 678.
Migration and Dynamics of Planets and Black Holes in Disks
Both planets and black holes embedded in disks (such as those around AGNs) can migrate due to gravitational interactions with the surrounding gas. Accretion of gas onto these bodies can change the direction and speed of their migration, sometimes even causing outward movement instead of the expected inward drift. This means that standard models of disk migration may not always apply near black holes, and special care is needed when predicting the movement of planets or black holes in these environments .
Black Holes Inside Planets and Stars
Dark matter could accumulate inside planets or stars and eventually collapse into a small black hole. If such a black hole forms and grows large enough, it could consume the host planet or star. Smaller black holes might evaporate, producing unusual heat flows or high-energy neutrinos, which could be detected as indirect evidence of their presence . Some researchers have even suggested that small singularities inside moons or planets could explain unexplained heat or magnetic field phenomena .
Conclusion
Planets can form and exist near black holes, especially in the disks around supermassive black holes in galactic centers. The intense environment near black holes can strip atmospheres from planets, potentially creating many rocky, possibly habitable worlds. Theoretical work also explores the possibility of small black holes within planetary systems, which could influence planetary dynamics and even contribute to dark matter. Ongoing and future observations may soon provide more direct evidence of these fascinating possibilities.
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