Search for Transmissions from Advanced Civilizations –“The Next Ten Years” (Weekend Feature)

 

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In September of 2015,  Andrew Siemion, Director of Berkeley SETI Research Center previewed the next decade's search for advanced extraterrestrial at a Congressional Hearing on Astrobiology. Although natural astrophysical sources produce a diverse array of electromagnetic, gravitational and high energy particle emission, there are particular types of emission that, as far as we know, could only be generated by an advanced technology. For example, technology constructed by human beings has been producing radio emission for more than 100 years that would be readily detectable at dozens of light years using receiving technology only moderately more advanced than our own. Some emissions, including that produced by the planetary radars at Arecibo Observatory and the NASA Deep Space Network, would be detectable across our galaxy.

Technologies far more advanced than our own could potentially produce even more dramatic evidence of their presence. Large stellar-scale structures could cause apparent modulation in starlight as they orbited their host, and massive energy usage by a super advanced civilization might be revealed by its thermodynamic signature, even from millions of light- years away.

 

Although we know of only one example of life anywhere in the universe, we have reasons to be optimistic about the possibility of life beyond Earth. Earth-like planets, water and complex chemistry have now been found in abundance throughout our galaxy. Everything that we believe was necessary for life to begin on Earth is now known to be ubiquitous throughout our galaxy and beyond. Knowing that extraterrestrial life could exist, the race is on to discover whether or not it, in fact, does exist.

Yet more compelling is the possibility that extraterrestrial life may have followed a similar developmental process as life on the Earth, and given rise to a life form possessing intelligence and a technological capability similar to, or perhaps far exceeding, our own. Conducting direct searches for advanced extraterrestrial life is the sole means of determining the prevalence of such life in the universe, and answering one of our most fundamental questions: Are we alone?

The motivation for radio searches for extraterrestrial intelligence can be summarized as follows:

Coherent radio emission is commonly produced by advanced technology (judging by Earth's technological development), 2. electromagnetic radiation can convey information at the maximum velocity currently known to be possible, 3. radio photons are energetically cheap to produce, 4. certain types of coherent radio emissions are easily distinguished from astrophysical background sources, 5. these emissions can transit vast regions of interstellar space relatively unaected by gas, plasma and dust. These arguments are unaffected by varying assumptions about the motivation of the transmitting intelligence, e.g. whether the signal transmitted is intentional or unintentional, and can be applied roughly equally to a variety of potential signal types or modulation schemes. Modern radio SETI experiments have been ongoing for the last 55 years, but for the most part they have searched only a small fraction of the radio spectrum accessible from the surface of the Earth and have probed only a few nearby stars at high sensitivity.

 

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Large national radio telescopes in the United States, such as the Green Bank Telescope in West Virginia and the Arecibo Observatory in Puerto Rico are superb facilities for a wide range of astronomy, including pulsar studies that could lead to the detection of low-frequency gravitational radiation, mapping the atomic and molecular content of nearby galaxies, and probing the earliest epochs of the universe. In addition, these facilities are among the world's best at searching for the faint whispers of distant technologies. The Green Bank Telescope and Arecibo Observatory can conduct observations across this entire range of the radio spectrum, from the natural low noise portion of the radio spectrum between 110 GHz, and the approximate locations in the radio spectrum where several different types of terrestrial transmitters produce emission.

 

                                        

Early in 2015, a group of astronomy, engineering and physics students and staff at UC Berkeley, working with colleagues from the National Radio Astronomy Observatory, installed a new instrument at the Green Bank Telescope that enables us to conduct SETI observations in parallel with other astronomers, a technique called "piggy-back" observing. This project was funded by a combination of support from the NASA Astrobiology Program, the National Science Foundation and the John Templeton Foundation, but NASA no longer provides funding for SETI experiments.

In addition to the Green Bank Telescope, other radio SETI programs are underway in the United States at Arecibo Observatory and the private Allen Telescope Array in Northern California. Many international radio telescopes are also currently being used for radio SETI searches, including the Low Frequency Array (LOFAR) in Europe, the Murchison Wideeld Array (MWA) in Australia and the Lovell Telescope at Jodrell Bank Observatory in the United Kingdom.

While the dominant paradigm in SETI research involves searching the radio portion of the electromagnetic spectrum, other wavelengths possess merit as well. Similar to consideration of radio emission from human technology as an example of a potentially detectable signal from extraterrestrial intelligences, we can conceive of ways in which human technologies operating at other wavelengths could produce signatures detectable at interstel lar distances. For example, laser technology already developed on Earth could be used to produce a signal that could outshine the sun by many orders of magnitude at a distance of more than 1000 lightyears.

These optical and infrared SETI experiments come in two varieties, searches for pulses of light of short duration and searches for light emission at a single wavelength using a spec trometer. Relative to radio transmissions, optical signals could potentially convey much more information content and are more easily focused for directed signaling or communication.

At one of the world's premier optical telescopes, the Keck Observatory on Mauna Kea, Hawaii, students and faculty at UC Berkeley are pursuing a search for continuous articial lasers, using optical spectra that are collected for the primary purpose of searching for and characterizing extrasolar planets. In an additional effort, a group led by students and faculty at UC San Diego are using the Lick Observatory, near San Jose, California, to conduct a search for pulsed lasers in the near-infrared part of the electromagnetic spectrum, wavelengths just a hair longer than optical light – the first SETI experiment ever to operate at this wavelength. Other optical SETI experiments are currently operating or under development at Harvard University and several research institutes in France and Italy.

The era of the "virtual observatory" has arrived. Many astronomers no longer need to travel thousands of miles to a telescope and command an instrument to perform observations. Hundreds of terabytes of astronomical data, collected with billion dollar telescopes, are now freely available. In many cases, these data are made available to the entire astronomical community the instant they are collected. These data undoubtedly contain many astronom ical discoveries that are as yet uncovered. Perhaps, if looked at very closely in a novel way, some of these data contain evidence of an extraterrestrial intelligence.

The astronomical literature is rife with speculation that very advanced intelligences may produce signatures detectable by traditional astronomical observations. Massive \Dyson" structures, so named after they were rst proposed by physicist Freeman Dyson, might be be built to harvest the energy of hundreds of Suns and could be detected in the latest generation of infrared sky surveys. A very advanced civilization using a naturally bright astronomical source as a pseudo-articial beacon, such as modulation of a naturally expanding and contracting star or interference with a pulsar, could be discovered through careful analysis of variable star or pulsar observations.

Researchers at Penn State University, led by Jason Wright, have recently under taken a signicant eort to search for evidence of massive energy usage by very advanced civilizations using data from NASA's WISE space telescope. Although so far this work has produced only negative results, it has placed signicant constraints on the presence of ex tremely advanced galactic-scale civilizations. Additional work led by Erik Zackrisson in Sweden and Prof. Michael Garrett in the Netherlands has come to similar conclusions regarding the rarity of super-advanced civilizations, but this collected work represents a promising and growing new area of SETI research.

It is undoubtable that the next decade will be an incredibly exciting time for astrobiology. Data provided by missions like the Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope (JWST) virtually guarantee dramatic new insights into exo planet science, including identifying and characterizing some of the nearest exoplanets to the Earth. At the same time, we will continue to learn more about the development of life on Earth and the potential for life elsewhere in our own Solar System. If history is any guide, these discoveries will only heighten our imagination about the possibilities for advanced life elsewhere in the Universe. Two of the most exciting prospects for advances in SETI research are described below.

The Breakthrough Prize Foundation has recently announced the Breakthrough Listen and Message Initiatives – two programs that will investigate the possibility of life beyond Earth and the relationship between humanity and life in the universe. Breakthrough Listen is a $100M 10-year eort to conduct the most sensitive, comprehensive and intensive search for advanced intelligent life on other worlds ever performed.

 

                                         

 

 

Using the GBT and Parkes, Breakthrough Listen will conduct deep observations of 1,000,000 of the nearest stars to the Earth that will be at least 10 times more sensitive than ever performed and will cover at least 5 times more of the radio spectrum. Break through Listen will also conduct an unprecedented complete survey of the entire plane of the Milky Way Galaxy, as well as surveys of more than 100 other galaxies, including all galax ies in the Milky Way's Local Group. The sensitivity of the Green Bank, expressed as the luminosity (power) detectable as a function of the transmitter distance, is shown in Figure

As shown, the Green Bank Telescope could detect an extraterrestrial radio transmitter with the same luminosity as our own most powerful radar (the Arecibo Planetary Radar), in 1 minute each, for more than 1 million nearby stars.

Using a robotic optical telescope at Lick Observatory, the APF with its "Levy Spectrometer," Breakthrough Listen will observe 1000 nearby stars and 100 galaxies searching for articial laser emission. These observations will be performed over wavelengths from 374950 nm, including the near ultraviolet, the entire visible, and near infrared portion of the electromagnetic spectrum. Breakthrough Listen will detect lasers with any power above 100 Watts from the nearest stars and above 1000 Gigawatts from the nearest galaxies.

The Square Kilometre Array (SKA) project is an international partnership that seeks to construct the world's largest radio telescope operating at meter and centimeter wavelengths, eventually achieving a full square kilometer (1 km2) of collecting area for some components.

 

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Such a telescope, as envisioned, would be the most powerful radio telescope in the world, surpassing all current facilities by an order of magnitude or more in sheer sensitivity. Phase I of the SKA is expected to be built in Southern Africa and Southern Australia, with the mid-frequency (centimeter-wave, SKA1-MID) and low frequency (SKA1-LOW, meter-wave) components split between the two sites respectively. The SKA Headquarters is located at the Jodrell Bank Observatory near Manchester, UK. There are 10 SKA member countries, and approximately 100 organizations from 20 countries participating in its development. The United States is not currently an SKA member country.

The SKA will offer revolutionary new observational capabilities for SETI, allowing sen sitive targeted SETI observations to be performed alongside other astronomical research. Rather than simply \piggy-backing," SETI observers will be able to independently point the telescope at targets of interest using high speed digital beamforming. SKA construc tion is expected to be completed in two phases. SKA Phase 1 will include a low frequency (SKA1-LOW, 50 350 MHz) array component made up of 130,000 dipole antennas sited in Southern Australia (Figure 7a) and a 200-dish mid-frequency (SKA1-MID, 350 14000 MHz) component sited in Southern Africa (Figure 7b). SKA Phase 2 will complete telescope con struction at both sites and could include augmentation with new mid-frequency aperture array technology that could dramatically expand the telescopes primary eld of view.

SKA may be the first telescope capable of detecting truly Earthlike leakage radiation from nearby stars, allowing us our best chance at detecting another civilization with an artificial radio signature similar to our own.

The Daily Galaxy via NASA Astrobiology: Dr Andrew Siemion at the Hearing on Astrobiology to the House Committee on Science, Space, and Technology on Tuesday, September 29, 2015.

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