It didn’t find anything. So far, this has been par for the course when it comes to the search for extraterrestrial life, better known by the shorthand SETI. Astronomers first began using telescopes to look for potential alien communication in 1960, and they have been met with silence ever since.

“I think when you’re doing a SETI project, it’s very important not to get discouraged by a null detection,” Tellis said. “SETI has been in process for about 60 years, and it’s been non-detection after non-detection after non-detection.”

Astronomers and engineers have spent that time developing more powerful technology to conduct SETI surveys. The majority of SETI searches have relied on radio telescopes, which scour the skies for signals in the radio and microwave parts of the light spectrum. In the 1960s, “lasers were new, tricky, low-power devices; by contrast, radio technology had been developing for decades and was relatively mature,” according to a history from the SETI group at Harvard.

These days, lasers can outshine the sun, albeit in tiny pulses. But a tiny pulse—preferably more than one, to prove it’s not a fluke—is all it would take for a distant, advanced civilization to tell Earth “hey, we’re here!” If humans can get really good at sending radio and laser signals, the reasoning goes, maybe intelligent civilizations beyond Earth can, too—and then send them our way.

Unlike radio SETI, optical SETI looks for signals in the visible portion of the light spectrum. Lasers travel well over galactic distances. The light, concentrated into a narrow beam that can be 10 times as bright as the sun, would experience less interference from interstellar dust and gas than radio waves might. Laser emissions are also capable of carrying massive amounts of information. The network of cables at the bottom of the ocean is a collection of pulses of light, firing at high frequencies to transmit digital data and bring us the internet.

The dataset Tellis used for his study contained thousands of observations of stars as young as 200 million years and stars as old as nearly 10 billion years. Keck’s instruments collected millions of photons of light from these stars. What Tellis and his algorithm looked for were brief surges in photons. The first run of the data reported 5,000 potential candidates for mysterious laser beams, but they were eventually ruled out, explained away as emissions from stars’ outer layers, cosmic rays from our sun, or internal reflections from telescope instruments. Tellis got some firsthand Keck time to observe at least one target, KIC 8462852, a star about 1,500 light-years from Earth. In 2015, astronomers announced the Kepler space telescope had observed an unusual dimming of its light, which some believe could be caused by structures built by an advanced civilization around the star. The light emission observed from KIC 8462852 was the best candidate for an alien laser beam in the survey before it was ruled out.