Ground to Dust: Collisional Cascades and the Fate of Kardashev II Megaswarms
Extraterrestrial intelligences are speculated to surround stars with structures to collect their energy or to signal distant observers. If they exist, these most likely are megaswarms, vast constellations of satellites (elements) in orbit around the hosts. Although long-lived megaswarms are extremel...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/adccc5 |
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| author | Brian C. Lacki |
| author_facet | Brian C. Lacki |
| author_sort | Brian C. Lacki |
| collection | DOAJ |
| description | Extraterrestrial intelligences are speculated to surround stars with structures to collect their energy or to signal distant observers. If they exist, these most likely are megaswarms, vast constellations of satellites (elements) in orbit around the hosts. Although long-lived megaswarms are extremely powerful technosignatures, they are liable to be subject to collisional cascades once guidance systems start failing. The collisional time is roughly an orbital period divided by the covering fraction of the swarm. Structuring the swarm orbits does not prolong the initial collisional time as long as there is enough randomness to ensure collisions, although it can reduce collision velocities. I further show that once the collisional cascade begins, it can develop extremely rapidly for hypervelocity collisions. Companion stars or planets in the stellar system induce perturbations through the Lidov–Kozai effect among others, which can result in orbits crossing within some millions of years. Radiative perturbations, including the Yarkovsky effect, also can destabilize swarms. Most megaswarms are thus likely to be short-lived on cosmic timescales without active upkeep. I discuss possible mitigation strategies and implications for megastructure searches. |
| format | Article |
| id | doaj-art-b753e22b8c2949baa3f5a0272ed1f1b8 |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-b753e22b8c2949baa3f5a0272ed1f1b82025-08-20T03:53:57ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01985219110.3847/1538-4357/adccc5Ground to Dust: Collisional Cascades and the Fate of Kardashev II MegaswarmsBrian C. Lacki0https://orcid.org/0000-0003-1515-4857Breakthrough Listen, Department of Physics , Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK ; astrobrianlacki@gmail.comExtraterrestrial intelligences are speculated to surround stars with structures to collect their energy or to signal distant observers. If they exist, these most likely are megaswarms, vast constellations of satellites (elements) in orbit around the hosts. Although long-lived megaswarms are extremely powerful technosignatures, they are liable to be subject to collisional cascades once guidance systems start failing. The collisional time is roughly an orbital period divided by the covering fraction of the swarm. Structuring the swarm orbits does not prolong the initial collisional time as long as there is enough randomness to ensure collisions, although it can reduce collision velocities. I further show that once the collisional cascade begins, it can develop extremely rapidly for hypervelocity collisions. Companion stars or planets in the stellar system induce perturbations through the Lidov–Kozai effect among others, which can result in orbits crossing within some millions of years. Radiative perturbations, including the Yarkovsky effect, also can destabilize swarms. Most megaswarms are thus likely to be short-lived on cosmic timescales without active upkeep. I discuss possible mitigation strategies and implications for megastructure searches.https://doi.org/10.3847/1538-4357/adccc5Search for extraterrestrial intelligenceTechnosignaturesCollisional processesAstrodynamicsOrbits |
| spellingShingle | Brian C. Lacki Ground to Dust: Collisional Cascades and the Fate of Kardashev II Megaswarms The Astrophysical Journal Search for extraterrestrial intelligence Technosignatures Collisional processes Astrodynamics Orbits |
| title | Ground to Dust: Collisional Cascades and the Fate of Kardashev II Megaswarms |
| title_full | Ground to Dust: Collisional Cascades and the Fate of Kardashev II Megaswarms |
| title_fullStr | Ground to Dust: Collisional Cascades and the Fate of Kardashev II Megaswarms |
| title_full_unstemmed | Ground to Dust: Collisional Cascades and the Fate of Kardashev II Megaswarms |
| title_short | Ground to Dust: Collisional Cascades and the Fate of Kardashev II Megaswarms |
| title_sort | ground to dust collisional cascades and the fate of kardashev ii megaswarms |
| topic | Search for extraterrestrial intelligence Technosignatures Collisional processes Astrodynamics Orbits |
| url | https://doi.org/10.3847/1538-4357/adccc5 |
| work_keys_str_mv | AT brianclacki groundtodustcollisionalcascadesandthefateofkardasheviimegaswarms |