If Loeb’s mother had been around at that point, he said, she would have tried to dissuade him from his late-career turn toward alien hunting. “She would say, ‘Why would you give up on everything you accomplished?’” Loeb has described his mother, Sara, as an “interrupted intellectual” whose family pulled her from college in Bulgaria to move to Israel upon its founding. When he and his two sisters were old enough, she continued her studies, and in Loeb’s adolescent years she took him along to college philosophy classes. They were very close; until her death in 2019, they spoke on the phone nearly every day. “I sort of realized on a personal level that, up until that point, I tried to make everyone happy,” he said. “After my parents passed away, I said: ‘The hell with it, I’ll focus on substance. I don’t care how many people like me or not like me, I would just do what seems to me is the right thing to do.’” Criticism from other astronomers only hardened his commitment. “The more pushback that I got,” he said, “the more appropriate it looked to me.”

Mainstream scientists might have been distancing themselves, but Loeb was discovering a different world of allies, fans and patrons. The newly revealed government interest in U.A.P.s got wealthy people wondering how to invest in the search for alien life. That led them, naturally, to Loeb. “I started getting money without soliciting it,” he told me. In May 2021, the Harvard astronomy-department administrator told Loeb that an anonymous donor had given him $200,000 in research funding. Within a few days, they determined that it came from a wealthy software engineer named Eugene Jhong. Loeb arranged a Zoom call with Jhong and got another $1 million. Around the same time, Frank Laukien, the chief executive of the scientific-instrument manufacturer Bruker, who had read Loeb’s book “Extraterrestrial,” showed up on his front porch in Lexington. Together they decided to establish the Galileo Project.

The observatory near Boston had been running for several months, and they were still training the machine-learning algorithms to identify birds, planes and other common airborne objects. The goal is to install up to 100 such observatories around the world; so far Loeb has obtained funding to install five more stations in the United States. While the dream is to get the first megapixel-quality photo of something anomalous, he says he expects almost everything these instruments detect to be mundane. “The Galileo Project is completely agnostic, has no expectations,” he told me. I asked him how an experiment like this could ever deliver a convincing negative result. A failure to photograph a U.A.P. would never convince a believer that there are no alien ships in the sky, only that the aliens were smart enough to avoid Loeb’s camera trap. “If we search the sky for five years, 24/7, and see nothing unusual except for birds and drones and airplanes, and we do it at tens of different locations, maybe 100 locations,” he said, “then we move on.”

The week after Loeb showed me the observatory, I joined a planning meeting for another Galileo Project initiative — an effort to retrieve an unusual meteorite that had fallen to Earth. Several years ago, Amir Siraj, a Harvard undergraduate working with Loeb, identified a curious entry in a government meteor database: On Jan. 8, 2014, an object exploded near Papua New Guinea. Its orbit suggested an origin outside our solar system, though it was impossible to say for sure because the government satellites that detected it were classified. In 2022, after a lot of prodding from Loeb, the U.S. Space Command released a letter saying with “99.999 percent confidence” that the Papua New Guinea fireball was interstellar. The government also published the meteor’s light curve, a graph of its brightness over time. From this, Loeb concluded that it had exploded so close to the Earth’s surface that it must have been made of something much harder than normal meteors, maybe even an artificial alloy like stainless steel. Which made him wonder: What if it was an extraterrestrial probe? And could he find its remains?

If anything was left of this meteor, or extraterrestrial probe, it was scattered across the seafloor north of Papua New Guinea. When meteors burn up in the atmosphere, the molten remains condense into sand-grain-size orbs called spherules that cascade to earth like glitter. The logistics of searching for those spherules under several thousand feet of water were daunting, but there was reason to think it could be done. In 2018, scientists used remotely operated vehicles and a “magnetic rake” to find spherules from a meteor that had fallen off the coast of Washington. Encouraged by that project, Loeb and Siraj started thinking about going after the Papua New Guinea meteorite. Charles Hoskinson, a mathematician who made a fortune in cryptocurrency, heard Loeb talking about the meteor on a podcast and pledged $1.5 million for the search. To figure out the logistics, they hired EYOS Expeditions, the company that helped the director James Cameron dive to the Pacific Ocean’s 36,000-foot-deep Mariana Trench. They planned to go to sea later in the spring.