Seminar and Journal Club

Jamie Holder
October 27, 2022
Zoom recording

Abstract:
Pulsed lasers provide a realistic method for communicating over interstellar distances. Using current-day technology, the intensity of the laser emission could be thousands of times brighter than the light from the host system star for the brief (~nanosecond) duration of the pulse. Searching for such emission requires a large optical light collector, coupled with fast photosensors and read-out electronics, and a method to discriminate these pulses from the large background due to Cherenkov emission from particle air showers in the Earth’s atmosphere. Imaging atmospheric Cherenkov telescopes, designed to study astrophysical gamma-ray sources at TeV energies, have similar requirements. I will describe the use of the VERITAS Cherenkov telescope array as an optical technosignature observatory, and discuss results from a survey of Breakthrough Listen targets. I will also discuss the potential for further synergies between ground-based gamma-ray astronomy and optical technosignature searches.

Wael Farah
October 20, 2022
Zoom recording

Abstract:
The Allen Telescope Array (ATA) is a 42-dish radio array hosted at the Hat Creek Radio Observatory, California, and is operated by the SETI Institute. For the last few years – after a decade of hibernation – the ATA has been undergoing a refurbishment program, and the instrument is now exiting its commissioning stage and commencing science observations with 20 elements outfitted with upgraded feeds. The cryogenically-cooled log-periodic feeds (also known as Antonio feeds) are more sensitive and robust compared to their earlier generation, and are receptive to a continuously wide range of frequencies, from 1 to 10 GHz.
In this presentation, I will describe the current hardware and software capabilities of the instrument. This includes the newly installed digitizer boards, the software correlator and beamformer, as well as the current and proposed observational capabilities of the telescope. Finally, I will also describe other experiments and instruments that are hosted on the Hat Creek Radio Observatory alongside the ATA.

Anamaria Berea
October 6, 2022
Zoom recording

Abstract:
In this paper I am exploring patterns of ubiquitous communication as a signal of successful communication evolution, that started local in various complex systems and became global. Intelligent communication is a coevolutionary process where innovation in artifactual communication (i.e., writing, telegraph, the Internet,…) and the type of collective behavior that forms a civilization intertwine and produce patterns such as universal transportation systems signals, universal brand logos, universal computer languages, and many more. The current “age of data” in our civilization is a result of two major forces: the global spread of artifactual means of communication (writing, computers, and the globalization of human languages) and the global spread of physical systems of recording and storing communication (the long evolution from Mesopotamian cuneiform tokens to current organizational servers and supercomputers). In alien languages, we would similarly expect for language to have coevolved with the social and technological evolution of that particular civilization. Globalized languages and large systems for communication are products of selection and adaptation mechanisms emerged from the economic systems of that civilization. At the large scale of the civilization, the planetary systems of interconnectivity for transportation and communication show artifactual, global patterns of signals and language of the largest magnitude known to us so far. I am also exploring a methodological reversal: can social and collective behavior laws that we find in cell-cell interactions, animal signaling and proto-human languages function as proxies for universal language patterns? Can we extrapolate from the empirical laws and statistical regularities of the social and collective phenomena in all these complex living systems to understand language evolution? We know that Zipf law applies both to languages and to complex systems such as cities or companies; we know that marginal analysis in economics (cost/benefit) also applies to metabolism and chemical communication in other species. What other laws from collective and social behavior of animals, humans and computers can we infer with respect to their universality and extrapolate on their probability to be found in alien languages?

Vishal Gajjar
September 29, 2022

Abstract:
For the past six decades, radio SETI has largely been focused on continuous-wave narrowband signals. In Gajjar et al. (2022), we demonstrated that broadband pulsed beacons are energetically efficient compared to narrowband beacons over longer operational timescales. We also reported the first extensive survey searching for such broadband pulsed beacons towards close to 2000 stars with the GBT. In this talk, I will talk about our detailed search strategy leveraging a convolutional neural network classifier on high-performance GPUs deployed for the very first time in a large-scale search for signals from ETIs. Using this classifier, we were able to reduce the number of false positives by 97%. Our selection criteria did not return any signals of interest. We thus place a constraint on the existence of broad-band pulsed beacons in our solar neighbourhood: <1 in 1000 stars have transmitter power densities >10^5 W/Hz.
For information about the speaker’s other work: gajjarvishal.com

Ashley Villar
September 22, 2022
Zoom recording

Abstract:
I will review the basic principles of anomaly detection and highlight ongoing efforts to use anomaly detection in astrophysical context, with an emphasis on SETI and time-series applications.

Slava Turyshev
September 15, 2022
Zoom recording

Abstract:
Nature has presented us with a very powerful “instrument” that we are yet to explore and put to use. This instrument is the Solar Gravitational Lens (SGL), which results from the ability of the gravitational field of the Sun to focus light from faint, distant targets. In the near future, a modest telescope with a coronagraph could operate in the focal region of the SGL and, using enormous amplification provided by the Lens, could provide multipixel images of exoplanets. We discuss the imaging properties of the SGL and introduce a mission concept to the SGL focal region that could provide us with direct, high-resolution images and spectroscopy of a potentially habitable Earth-like exoplanet. A meter-class telescope operating at the focal region of the SGL could yield ~(450×450)-pixel images of an “Earth 2.0” at distances up to 100 light years (~30 parsec) with spatial resolution high enough to see its surface features and to determine and study the signs of habitability. We address aspects of mission design and spacecraft requirements, as well as capabilities needed to fly this mission in the next two decades. We also discuss technologies for fast transit through the solar system that will be demonstrated during our ongoing NIAC Phase III study. For background, please check: https://www.youtube.com/watch?v=NQFqDKRAROI

Jason Wright
September 8. 2022
Zoom recording

Abstract:
I will review the Ĝ search for extraterrestrial technology via its waste heat, in particular its searches for galaxy-spanning industry. I will conclude with the participants about the best next steps, including how to add more detailed SED and spectral synthesis to better constrain waste heat components in the Ĝ sample.

Macy Huston & Nick Tusay
March 24, 2022
Zoom recording

Abstract:
Stars provide an enormous gain for interstellar communications at their gravitational focus, perhaps as part of an interstellar network. If the Sun is part of such a network, there should be probes at the gravitational foci of nearby stars. If there are probes within the solar system connected to such a network, we might detect them via transmissions to them from relays at these foci. Here, we demonstrate a search across a wide bandwidth for interstellar communication relays beyond the Sun’s innermost gravitational focus at 550 AU using the Green Bank Telescope (GBT) and Breakthrough Listen (BL) backend. As a first target, we search for a relay at the focus of the Alpha Centauri AB system while correcting for the parallax due to Earth’s orbit around the Sun. We searched for radio signals directed at the inner solar system from such a source in the L and S bands. Our analysis, utilizing the turboSETI software developed by BL, did not detect any signal indicative of a non-human-made artificial origin. Further analysis was done to exclude false negatives and signals from the nearby target HD 13908. Assuming a conservative gain of 10^3 in L-band and roughly 4 times that in S-band, a ~1 meter directed transmitter would be detectable by our search above 7 W at 550 AU or 23 W at 1000 AU in L-band, and above 2 W at 550 AU or 7 W at 1000 AU in S-band. Finally, we discuss the application of this method to other frequencies and targets.

Jacob Haqq-Misra
March 17, 2022
Zoom recording

Abstract:
Atmospheric pollution is one consequence of global-scale technology on Earth. Some technology elevates existing levels of atmospheric constituents in the atmosphere, while other industrial processes can contribute novel pollutants that would not otherwise be present. The detection of such pollutants in the atmosphere of an exoplanet would be compelling evidence for the existence of extraterrestrial technology. In this talk, I discuss the possibility of detecting technosignatures that could arise from planets with elevated levels of chlorofluorocarbons and other pollutants with current and planned observatories.