Three scenarios of an exoplanet encountering a primordial black hole
A three-body numerical simulation was performed for the encounter of a primordial black hole (PBH) with the TOI 2796 system, which includes a hot Jupiter. Over a 100-day time span, three dynamical outcomes were identified: (i) ejection of the planet; (ii) formation of a stable triple system with a semi-major axis of ~1 AU and a period of ~5 days; (iii) capture of the planet by the black hole into a binary system with a semi-major axis of 0.0194 AU and a period of 15 days, which then departs from the star. The results reveal a nontrivial diversity of orbital evolutions during a PBH close encounter and point to the potential contribution of such objects to the restructuring of planetary systems.
Context
Primordial black holes (black holes), formed in the first moments after the Big Bang, an idea proposed by Georges Lemaître, remain one of the main candidates for dark matter. Their existence could explain the hidden mass of the Universe, as indicated by Vera Rubin through galaxy rotation. If such objects pass through planetary systems, they can leave gravitational "fingerprints" — from subtle orbital anomalies to complete system disruption. Understanding these scenarios is crucial for interpreting future observational data, including gravitational microlensing and gravitational waves, as well as for testing Stephen Hawking's predictions about black hole evaporation.
Methods
The study used direct numerical integration of the three-body problem with the adaptive LSODA solver, which automatically switches between Adams and backward differentiation methods. The system modeled consisted of a Sun-like star (TOI-2796), its hot Jupiter (TOI-2796 b), discovered by the transit method and confirmed by spectroscopy, and a hypothetical primordial black hole (PBH) with masses ranging from 15 to 500 solar masses. Initial conditions were varied to cover different impact parameters. To search for rare scenarios such as planet capture, a neural network was trained on 475 simulations, which allowed finding a configuration with the formation of a PBH–planet binary system.
Results
Over 100 days of simulation, three outcomes emerged. With a PBH of 15 solar masses, the planet was ejected from the system, moving to a distance of more than 2 AU in just 16 days. In the scenario with a PBH of 500 solar masses, a stable triple system formed: the PBH orbited the star (TOI-2796) at a distance of about 1 AU with a period of approximately 5 days, with the orbit slightly expanding over time. Finally, the neural network revealed a case with a 300-solar-mass PBH, where the planet (TOI-2796 b) was captured by the black hole into a compact pair with a semi-major axis of 0.0194 AU and an orbital period of 15 days; during the simulation, this pair moved away from the star to 51.5 AU. These numbers demonstrate the sensitivity of the outcome to the mass and trajectory of the PBH.
Implications
The results show that primordial black holes can act not only as destroyers but also as architects of planetary systems. The capture scenario suggests the possibility of hidden populations of planets orbiting PBHs far from stars, which could explain some anomalies in the distribution of exoplanets. If PBHs constitute part of dark matter, such events could leave observable traces, such as unusually high eccentricities in isolated planets. This also opens a new approach to testing Vera Rubin's hypothesis of invisible mass through the dynamics of planetary bodies.
Future development
Further research may include accounting for relativistic effects, such as the emission of gravitational waves during close encounters, and modeling the long-term evolution of captured systems. With the launch of new observatories like James Webb and the future Vera Rubin telescope, it will become possible to search for predicted orbital distortions in nearby exoplanets. Additionally, studying cometary clouds around stars perturbed by PBH flybys could provide additional observational clues.
Impact
The impact spans exoplanet observational astronomy exoplanets and dark matter cosmology: searching for orbital anomalies in planets could become a new method for detecting PBHs, complementing microlensing and gravitational wave observations.
Next steps
The immediate next step is to extend the simulations to longer timescales using high-accuracy integrators to verify the stability of triple systems and to estimate the probability of different outcomes depending on PBH parameters.
Key open problems
The work is directly connected to the puzzle of dark matter: if PBHs exist, they could explain the hidden mass, but their nature remains unconfirmed. Moreover, the three-body problem in the context of planetary systems illustrates chaotic dynamics that can lead to unexpected architectures observed in many exoplanets, and raises the question of the role of initial conditions in forming stable systems.
🎯 If a 300-solar-mass primordial black hole passed through the Solar System at Earth's orbital distance, the consequences would be catastrophic: our planet would likely be ejected into interstellar space, sending us on an eternal journey in darkness.
Key numbers
- distance in capture scenario: 51.5 AU
- triple system period: ~5 days
- semi-major axis of captured pair: 0.0194 AU
- simulation time: 100 days
- number of training runs: 475