The Breakthrough Listen Search For Intelligent Life Near the Galactic Center I (2104.14148v1)

Abstract: A line-of-sight towards the Galactic Center (GC) offers the largest number of potentially habitable systems of any direction in the sky. The Breakthrough Listen program is undertaking the most sensitive and deepest targeted SETI surveys towards the GC. Here, we outline our observing strategies with Robert C. Byrd Green Bank Telescope (GBT) and Parkes telescope to conduct 600 hours of deep observations across 0.7--93 GHz. We report preliminary results from our survey for ETI beacons across 1--8 GHz with 7.0 and 11.2 hours of observations with Parkes and GBT, respectively. With our narrowband drifting signal search, we were able to place meaningful constraints on ETI transmitters across 1--4 GHz and 3.9--8 GHz with EIRP limits of $\geq$4$\times$10$^{18}$ W among 60 million stars and $\geq$5$\times$10$^{17}$ W among half a million stars, respectively. For the first time, we were able to constrain the existence of artificially dispersed transient signals across 3.9--8 GHz with EIRP $\geq$1$\times$10$^{14}$ W/Hz with a repetition period $\leq$4.3 hours. We also searched our 11.2 hours of deep observations of the GC and its surrounding region for Fast Radio Burst-like magnetars with the DM up to 5000 pc cm$^{-3}$ with maximum pulse widths up to 90 ms at 6 GHz. We detected several hundred transient bursts from SGR J1745$-$2900, but did not detect any new transient burst with the peak luminosity limit across our observed band of $\geq$10$^{31}$ erg s$^{-1}$ and burst-rate of $\geq$0.23 burst-hr$^{-1}$. These limits are comparable to bright transient emission seen from other Galactic radio-loud magnetars, constraining their presence at the GC.

• The paper reports that 600 hours of targeted radio observations detected no persistent narrowband ETI signals, setting strong EIRP constraints.
• It employs both narrowband and novel broadband (negative dispersion) searches, expanding SETI methodologies and parameter spaces.
• The findings underscore the need for enhanced sensitivity and wider bandwidths to capture potential extraterrestrial technological signals.

Analyzing the Breakthrough Listen Survey for Intelligent Life Near the Galactic Center

This paper titled "The Breakthrough Listen Search For Intelligent Life Near the Galactic Center I", authored by Gajjar et al., represents a methodical investigation into the potential existence of extraterrestrial intelligence (ETI) in the vicinity of the Galactic Center (GC). Employing state-of-the-art radio telescope technology, the paper articulates the methodology, preliminary findings, and implications of this comprehensive SETI (Search for Extraterrestrial Intelligence) survey.

Observational Strategy and Methodology

The Breakthrough Listen Initiative's approach centers on leveraging the capabilities of the Green Bank Telescope (GBT) and Parkes Telescope to perform targeted radio frequency surveys from 0.7 to 93 GHz. Specifically, this paper highlights observations conducted between 1 to 8 GHz using 600 hours of allocated telescope time. The line-of-sight towards the GC offers a prime observation path due to the concentration of stars and potentially habitable zones in that region. The survey's dual methodology comprises targeted searches for both narrowband signals—indicative of technological transmissions—and temporally dispersed broadband signals, which might suggest deliberate communicative attempts by an advanced civilization.

Results and Constraints

The results presented in this paper related to the search for narrowband ETI signals across the observed frequencies. The analysis reports a non-detection of persistent narrowband signals that meet the threshold criteria, thus placing robust constraints on the presence of powerful constant beacons in the surveyed direction. The limits are characterized by equivalent isotropic radiated power (EIRP) constraints of ≥4×10¹⁸ W for the Parkes observations and ≥5×10¹⁷ W for GBT within 60 million and half a million stars, respectively.

Moreover, the survey undertakes an innovative attempt to detect artificially dispersed broadband transient signals with negative dispersion measures, a signal structure not naturally occurring and potentially indicative of intelligent origin. This attempt to explore non-traditional signal structures highlights the proactive expansion of SETI parameter spaces beyond standard methodologies.

Implications and Future Directions

The absence of detectable ETI signals in these frequency bands and surveyed regions suggests either the rarity of technologically active civilizations transmitting in our direction or possibly signals at levels below current detection capabilities. This outcome underscores the necessity to improve upon survey sensitivities and explore wider bandwidths and other forms of potential technosignatures.

The paper also deliberates on the technological and energetic implications necessary for civilizations capable of generating detectable signals from such vast distances, highlighting the energy inefficiency of continuous powerful narrowband beacons.

Conclusion

While the Breakthrough Listen survey towards the GC has yet to unveil evidence of extraterrestrial technology, the comprehensive and methodical approach establishes significant constraints and extends the known parameter space for future SETI endeavors. Future efforts may direct their focus on enhancing detection technologies, increasing temporal coverage, and implementing novel strategies to further discern the noise-ridden cosmic environment for signs of intelligent life beyond Earth. This paper contributes meaningfully to the collaborative global pursuit of unveiling the mysteries of cosmic habitats and technological presences beyond our own.