Artist’s impression of an Earth-like exoplanet. Image : ESO/M. Kornmesser

The Breakthrough Listen project has completed a sweeping search of over 1,300 nearby stars for signs of alien technology. Sadly, no evidence of extraterrestrials was found, but the $100 million project took a major leap forward in terms of its ability to continue the search.




If at first you don’t succeed, try again—but with better tools and refined techniques.

Such is the feeling right now among researchers involved with the Breakthrough Listen project, a 10-year initiative founded in 2015 by Israeli-Russian billionaire Yuri Milner and the late physicist Stephen Hawking. Based at the SETI Research Center at the University of California, Berkeley, the project aims to find signs of an extraterrestrial civilization. Researchers are scanning the cosmos using t he Green Bank Radio Telescope (GBT) in West Virginia and CSIRO’s Parkes Radio Telescope in Australia, among other tools.


The Breakthrough Listen team recently completed a comprehensive scan of 1,372 nearby stars, but no evidence of aliens was detected over the course of the three-year survey. It might seem like a disappointing result, but the project set the stage for more ambitious and sophisticated searches that are already underway. The work also resulted in two new research papers, both of which are set to be published in the Astrophysical Journal.

The endeavor generated a whopping one petabyte (PB), or one million gigabytes, of optical and radio telescopic data, which is being made available to the public. As a Breakthrough Listen press release pointed out, it’s now the largest release of SETI data to date.

“I am not at all discouraged,” said study co-author Andrew Siemion when asked about the outcome of the latest search. “Seeing these new results submitted for publication is heartening in and of itself,” he told Gizmodo in an email. “These results will also help lead us toward further analysis that will place yet more stringent limits on the distribution of technologically capable life in the universe and give us a better shot at detecting something if it’s out there.”

Likewise, the lead researcher behind the Breakthrough Listen project, Danny Price, said he wasn’t disheartened by the results.


“We knew going in that it was incredibly challenging, and we are still learning more about our data, creating new algorithms—and we’ll be bringing in new telescopes in the future,” he told Gizmodo in an email.

The 100 meter Green Bank telescope. Image : Green Bank Observatory


The latest search involved an analysis of 1,372 stars out of a total sample pool of of 1,702 stars, none of which are farther than 160 light-years away. The survey included a wider variety of star types than usual, including stars that aren’t similar to our Sun.

As the new project demonstrated, however, the search for extraterrestrial intelligence, or SETI, has come a long way since its humble beginnings in the early 1960s, when astronomer Francis Drake began to search in earnest for intelligent aliens. For the most part, conventional SETI focused on the search for radio communication leakage, but the big new idea now employed by SETI researchers is the hunt for technosignatures, that is, evidence of advanced alien technologies. This can include signatures produced by communications systems, propulsion devices, megascale engineering projects (such as Dyson spheres), and even industrial waste, among many other possibilities. Accordingly, SETI researchers are honing their methods and technologies to tune in to the applicable wavelengths.


The Breakthrough Listen program works by scanning the electromagnetic spectrum for signatures, or emissions, consistent with what we think we know about advanced alien technologies, but are at the same time inconsistent with natural phenomena.


“We like to make as few assumptions as possible, so we are surveying a large range of radio frequencies,” said Price, referring to the 1 to 10 gigahertz (GHz) range, “which is mainly limited by the receivers of the telescopes.”

His team is looking for signals that appear artificial—and not astrophysical—within this range, while also looking for bright laser transmissions with optical telescopes, namely the Automated Planet Finder Telescope at Lick Observatory in California. The researchers are using machine learning-driven algorithms to sift through the troves of data. SETI and the revolution in Big Data are now intersecting in a big way; the recent search yielded 1 PB worth of data, but the Breakthrough Listen team expects the size of the archive to grow to around 25 PB over the next several years.


“It is possible to publish meaningful SETI results in mainstream journals, it is possible to get a PhD doing SETI research, and importantly, it is possible to include SETI research in a productive scientific career.”

Indeed, what was once considered a fringe activity bordering on pseudoscience is quickly becoming a rigorous, well-respected scientific discipline in its own right, thanks to contributions from astronomers, astrophysicists, astrobiologists, computer scientists, and experts in artificial intelligence and Big Data.




“I think we owe this change to a number of factors—the certainty with which we now know that exoplanets are extremely common being very high on the list,” Siemion told Gizmodo. “But also very important is the way in which modern SETI practitioners have demonstrated that SETI need not be a field starved of publications and academic engagement. It is possible to publish meaningful SETI results in mainstream journals, it is possible to get a PhD doing SETI research, and importantly, it is possible to include SETI research in a productive scientific career.”

Jill Tarter, the chair emeritus for SETI Research at the SETI Institute, is “very enthusiastic” about the new work. From 1994 to 2004, the SETI Institute conducted Project Phoenix, in which its researchers scanned around 800 stars in the 1 to 3 GHz range from multiple observatories.




“Breakthrough Listen is doing the same sort of search, but better,” wrote Tarter in an email to Gizmodo. “They’ve built wonderful signal processing backends that can record wider bandwidths and thus search more rapidly. They have new analysis software and a nascent neural network tool to search for more varied types of signals. In this decade, they will be able to search a lot more parameter space than we were able to with Project Phoenix—that’s great progress. But it is still a vast cosmos out there, and it may take a while before success is achieved, assuming there are signals to be found.”

“Particularly novel here is that they are releasing all of their data, so anyone can search to see if they might have missed anything, follow up on their best candidate signals—all of which were classified by the team as radio frequency interference from human-made technology—or calculate exactly how sensitive they were to various kinds of signals,” Jason Wright, an astronomer at Pennsylvania State University, said in an email to Gizmodo. “This in itself is a huge challenge.” Wright wasn’t involved with the new project but has worked with Breakthrough Listen in the past.


Hector Socas-Navarro, an astronomer at the Canary Islands Institute of Astrophysics, said Breakthrough Listen is an interesting collaboration between academic institutions and private philanthropy. He’s “not particularly optimistic” about our chances of finding extraterrestrial civilizations through radio emissions, but he believes this effort is “absolutely necessary” because the potential implications are “enormous.” We have no idea of what the chances of success actually are, but we “have to at least try our best,” he said.



“But also because, while doing this systematic survey of the sky in radio wavelengths, we are also learning about the universe,” Socas-Navarro told Gizmodo in an email. “It leads to very valuable science. Advances in astronomical instrumentation, artificial intelligence for data analysis and cosmic signals such as FRBs (fast radio bursts) have been driven by SETI efforts and, in particular, by Breakthrough Listen.”


The MeerKAT radio telescope array in South Africa. Image : SKA

Looking ahead, the Breakthrough Listen scientists would like to tune into different frequencies and attempt to hone in on a wider variety of signal types. And of course, they’d like to target more stars.




Many, many more stars.

The team will be working with the MeerKat radio telescope array in South Africa. This instrument will allow the team to cover the same frequency range documented in the new papers, but at a higher sensitivity—and, crucially, will involve search of over 1 million nearby stars.


“That’s three orders of magnitude improvement,” said Siemion.

Correction: A previous version of this article said that the latest search had completed scanning 1,702 stars; in fact, it analyzed 1,372 stars out of a total sample of 1,702 stars.