Fast Radio Bursts from Extragalactic Light Sails

Abstract: We examine the possibility that Fast Radio Bursts (FRBs) originate from the activity of extragalactic civilizations. Our analysis shows that beams used for powering large light sails could yield parameters that are consistent with FRBs. The characteristic diameter of the beam emitter is estimated through a combination of energetic and engineering constraints, and both approaches intriguingly yield a similar result which is on the scale of a large rocky planet. Moreover, the optimal frequency for powering the light sail is shown to be similar to the detected FRB frequencies. These `coincidences' lend some credence to the possibility that FRBs might be artificial in origin. Other relevant quantities, such as the characteristic mass of the light sail, and the angular velocity of the beam, are also derived. By using the FRB occurrence rate, we infer upper bounds on the rate of FRBs from extragalactic civilizations in a typical galaxy. The possibility of detecting fainter signals is briefly discussed, and the wait time for an exceptionally bright FRB event in the Milky Way is estimated.

• The paper hypothesizes that Fast Radio Bursts (FRBs) could be artificial beams used by extragalactic civilizations to power light sails, estimating the required beam emitter size to be twice Earth's diameter.
• The study finds the energetic and engineering constraints, including emitter size, optimal frequency, and power emission, are compatible with sustaining a relativistic light sail for a payload of around 10^6 tons.
• This hypothesis suggests FRBs could be detectable signs of advanced technology, with potential distinguishing signal patterns and implications for estimating the prevalence of extragalactic civilizations.

Analysis of Fast Radio Bursts as Potential Signals from Extragalactic Civilizations

The paper "Fast Radio Bursts from Extragalactic Light Sails," authored by Manasvi Lingam and Abraham Loeb, presents an intriguing hypothesis about the origin of Fast Radio Bursts (FRBs). The authors propose that these enigmatic and energetic cosmic events could be artificial in nature, possibly emanating from extragalactic civilizations that employ them as a means to power large light sails. This perspective provides a refreshing, if speculative, approach to understanding FRBs, which are typically considered to have natural astrophysical origins.

Key Hypotheses and Numerical Estimations

The central hypothesis of the paper is that FRBs might be manifestations of beams used by extraterrestrial societies to propel large spacecraft via light sails. The study explores the compatibility of the parameters associated with FRBs, such as their energy output and frequency, with the theoretical requirements for such an artificial propulsion system.

1. Beam Emitter Size and Frequency:
   • The authors calculate the diameter of the beam emitter required to generate FRBs and find it to be on the order of a large rocky planet, approximately twice the Earth's diameter. This estimate is derived independently from energetic and engineering constraints, providing a consistent result.
   • The optimal frequency for the postulated propulsion system aligns well with those observed for FRBs, further supporting the potential viability of the hypothesis.
2. Energetic and Engineering Constraints:
   • By assuming the use of stellar energy and a specific coolant for the beam emitter, the energetics required to sustain such beams are evaluated. The authors derive that the typical power emission matches that necessary for sustaining a relativistic light sail.
3. Light Sail and Beam Characteristics:
   • The conceptual spacecraft, propelled by the hypothesized beams, could feature a payload mass of around $10^6$ tons. This would position the spacecraft sizeably above other known or speculated propulsion project designs, suggesting a significant technological capability.
   • The characteristic angular velocity of the beams, inferred from typical FRB durations, is proposed to be rationalized through the movement of the emission system.

Implications for the Search for Extraterrestrial Intelligence (SETI)

The implications of this hypothesis extend deeply into speculative SETI research, suggesting that if FRBs indeed partly originate from technological activities, they represent a form of communication or propulsion observation at cosmological distances.

• Quantifying Extragalactic Civilizations:
  • Considering the current rate of observed FRBs and the number of habitable planets, the paper posits an upper limit on the number of advanced civilizations capable of emitting such signals, suggesting fewer than 10,000 per galaxy.
• Prospect for Detection:
  • The study highlights the potential to distinguish natural from artificial origins by examining specific signature patterns in the received signals, such as their multi-peaked nature that can result from a moving light sail.

Future Prospects and Theoretical Impact

The proposition that FRBs might be of artificial origin introduces a novel dimension to astrophysical and SETI research, encouraging the community to explore this possibility despite its speculative nature. This theory prompts a reassessment of FRB characteristics and their potential indications of advanced extraterrestrial technology.

While recognizing the primarily speculative foundation of their study, Lingam and Loeb's examination prompts meaningful debate and analysis regarding non-traditional astrophysical phenomena interpretations. As observational techniques improve and data collection expands, further scrutiny of FRBs will be essential to determine the validity of their proposal. The emphasis on distinguishing between natural and potential artificial sources will likely influence search strategies in the field.