SEATTLE, February 14, 2020 (Breakthrough Initiatives PR) – The Breakthrough Listen Initiative today released data from the most comprehensive survey yet of radio emissions from the plane of the Milky Way Galaxy, the region around its central, 4-million-solar-mass black hole, and observations of the interstellar comet 2I/Borisov.
Breakthrough Listen Principal Investigator Andrew Siemion announced the release of the nearly two petabytes of data at the annual meeting of the American Association for the Advancement of Science. It marks the second “data dump” from the four-year-old, $100M search for extraterrestrial intelligence (SETI) initiative. A first download of a petabyte of radio and optical telescope data was released in June 2019, marking the largest release of SETI data in the history of the field.
The raw data – yet to be fully analyzed by astronomers – comes from a survey of the radio spectrum between 1 and 12 gigahertz (GHz). About half was captured via the Parkes Radio Telescope in New South Wales, Australia, which, because of its location in the Southern Hemisphere, is perfectly situated and outfitted to scan the entire galactic disk and galactic center. Parkes is part of the Australia Telescope National Facility, owned and managed by the country’s national science agency, CSIRO.
“The galactic center – the most extraordinarily energetic area of our galaxy, is an integral focus of our data gathering with all of our facilities,” said Siemion. “It is there that an advanced civilization might somehow harness the energy of the supermassive black hole at the center of the Milky Way Galaxy to signal its existence.”
The remainder of the dataset was recorded by the Green Bank Observatory in West Virginia (the world’s largest steerable radio dish), and the Automated Planet Finder (an optical telescope built and operated by UC Berkeley, and located at Lick Observatory outside San Jose, California).
Breakthrough Listen, based at UC Berkeley, is supported by a $100 million, 10-year commitment from the Breakthrough Initiatives, founded in 2015 by Yuri and Julia Milner to explore the universe, seek scientific evidence of life beyond Earth and encourage public debate from a planetary perspective.
“For the whole of human history, we had a limited amount of data to search for life beyond Earth. So all we could do was speculate. Now, as we are getting a lot of data, we can do real science – and, with making this data available to the general public, so can anyone who wants to know the answer to this deep question,” said Yuri Milner, Founder of Breakthrough Initiatives.
“Since the first Breakthrough Listen data release last June, we have doubled the amount of data captured and made publicly available,” said Breakthrough Listen lead system administrator Matt Lebfosky. “We are excited by the many use cases for this information, and it is our hope these data sets will ultimately reveal new insights – be it evidence of other intelligent life in the universe or as-yet-undiscovered natural astronomical phenomena.”
Earth Transit Zone Survey
In releasing the new radio and optical data, Siemion highlighted an initial analysis of a small subset of radio emissions from 20 nearby stars that are aligned with the plane of Earth’s orbit – the Earth Transit Zone. These stars are situated such that an advanced civilization located around them could observe the Earth pass in front of our sun (a “transit” like those identified by NASA’s Kepler and TESS space telescopes).
Conducted by the Green Bank Telescope, the Earth Transit Zone Survey took observations in the radio frequency range between 4 and 8 gigahertz, the so-called C-band. The data were then analyzed by former UC Berkeley undergraduate Sofia Sheikh, now a graduate student at Pennsylvania State University, who looked for bright emissions at a single radio wavelength or a narrow band around a single wavelength. She submitted her analysis of these observations to the Astrophysical Journal.
“This is a unique geometry of the Earth Transit Zone” Sheikh said. “It is the method that we on Earth have used to discover other exoplanets, so we can imagine that this same geometry might be how other intelligent species find planets such as ours, as well.”
In Sheikh’s research, she pointed the Green Bank Telescope at each star for five minutes, pointed away for another five minutes, and repeated that process twice more. She then eliminated any signal that didn’t disappear when the telescope was pointed away from the star. Using this method she sorted through an initial million radio spikes – eliminating those caused by Earth-based signal interference. Ultimately, the last four unexplained signals turned out to be from passing satellites.
While Sheikh and her team found no technosignatures of civilizations, their analysis and other detailed studies conducted by the Breakthrough Listen group are gradually narrowing potential locations and capabilities of advanced civilizations that could exist in our galaxy.
“Because I purposely looked at nearby targets, my search was sensitive enough to locate a transmitter on par with the strongest transmitters on Earth,” Sheikh said. “We can infer that there is nothing as strong as our Arecibo telescope beaming a signal toward us. Even though this is a very small project, we are starting to get at new frequencies and new areas of the sky.”
Sheikh noted that her mentor, Jason Wright at Penn State, estimated that if the world’s oceans represented every place and wavelength we could search for intelligent signals, we have, to date, explored only a hot tub’s worth of it.
“We didn’t find aliens, but we are setting very rigorous limits on the presence of a technologically capable species, by screening for the first time for data between 4 and 8 gigahertz on the radio spectrum,” Siemion said. “These results notch another rung on the ladder for the next team who comes along and wants to improve on our experiment.”
Visit from an interstellar comet, 2I/Borisov
Breakthrough Listen also released observations of the interstellar comet 2I/Borisov, which had a close encounter with our sun in December 2019, and is now on its way out of the solar system. The group had earlier scanned the interstellar rock, ’Oumuamua, which passed through the center of our solar system in 2017. Neither exhibited technosignatures.
“If interstellar travel is possible and if other civilizations are out there (all of which we don’t know), and if they are motivated to build an interstellar probe, then some fraction greater than zero of the objects that are out there are artificial interstellar devices,” said Steve Croft, a research astronomer with the Berkeley SETI Research Center and Breakthrough Listen. “Just as we do with our measurements of transmitters on extra-solar planets, we want to put a limit on what that number is.”
According to Siemion, Breakthrough Listen looks for electromagnetic radiation that is consistent with a signal that we know is produced by technology and is inconsistent with the background noise from natural astrophysical events. This also requires eliminating signals from cellphones, satellites, GPS, internet, WiFi, and myriad other human sources.
Siemion emphasizes that the Breakthrough Listen team intends to analyze all data released to date, systematically and iteratively. Only 20 percent of the captured data have been analyzed thus far.
NRAO Partners with SETI Institute
Marking a milestone in the growth of the SETI community internationally, the National Radio Astronomy Observatory (NRAO) and the privately-funded SETI Institute also announced an agreement to add SETI capabilities to radio telescopes operated by NRAO. The first project will develop a system to piggyback on the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and provide data to state-of-the-art digital back-end SETI Institute equipment.
“This important collaboration is a wonderful leap forward for the global SETI effort – bringing together teams of dedicated researchers and additional telescopes, and boosting the capacity and rigor with which we scan the skies,” said Siemion, who in addition to his position at the University of California, Berkeley is the Bernard M. Oliver Chair for SETI at the SETI Institute. “This interface with the VLA will allow us to conduct a powerful, wide-area SETI survey that will be vastly more complete than any previous such search.”
“As the VLA conducts its usual scientific observations, this new system will allow for an additional and important use for the data we’re already collecting,” said NRAO Director Tony Beasley. “Determining whether we are alone in the universe as technologically capable life is among the most compelling questions in science, and NRAO telescopes can play a major role in answering it.”