Avi Loeb

• 1. Introduction

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  In 2024, Avi Loeb stood before an audience and declared his view that the Messiah will be an alien arriving from outer space. Loeb is an Israeli-American theoretical physicist whose formal name is Abraham Loeb. He was born on the 26th of February 1962. He works on astrophysics and cosmology, and he has written popular science books alongside technical textbooks. Since 2017 he has also argued, again and again, that alien spacecraft may be passing through our Solar System. Most of his colleagues reject that idea. So how does a scientist with a long record in mainstream research end up here? What did he actually claim, and what did other experts find when they checked his evidence? And why do critics say the real problem lies in the way he presents his results?

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• 2. Talpiot To Harvard

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  Beit Hanan, a place in Israel, is where Loeb was born. At age 18, while serving in the Israeli Defense Forces, he entered the Talpiot research program. Through it he earned a BSc in physics and mathematics in 1983, an MSc in physics in 1985, and a PhD in plasma physics in 1986. All three degrees came from the Hebrew University of Jerusalem. During his doctoral work he did research at the Soreq Nuclear Research Center in Yavne. His thesis modeled the acceleration of charged particles in plasma.

  From 1983 to 1988, the U.S. Strategic Defense Initiative invited him to work on a new propulsion method for high-speed projectiles. Between 1988 and 1993 he was a long-term member of the Institute for Advanced Study at Princeton. There he turned to theoretical astrophysics under the supervision of John Bahcall.

  Harvard University hired him in 1993 as an assistant professor of astronomy, and he received tenure three years later. In 2007 he became director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics. He chaired the astronomy department from 2011 to 2020, and in 2012 he became the Frank B. Baird Jr. Professor of Science. In 2016 he founded the Black Hole Initiative. Within a year, he began making the claims about alien spacecraft that would shape his public image.

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• 3. Cosmic Predictions

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  Eight books carry Loeb's name, among them the textbooks How Did the First Stars and Galaxies Form? and The First Galaxies in the Universe. His papers range across the first stars, massive black holes, gamma-ray bursts, and the future collision between the Milky Way and Andromeda galaxies. He has also worked on imaging black hole silhouettes.

  Some of his work made bold predictions. With his postdoc James Guillochon, he predicted a population of stars moving near the speed of light through the universe. With John Forbes and Howard Chen of Northwestern University, he proposed that the black hole Sagittarius A* has transformed sub-Neptune-sized exoplanets into rocky super-Earths.

  Dark matter drew his attention too. In 2013, working with Paolo Pani, he showed that primordial black holes with masses between the Moon and the Sun cannot make up dark matter. In 2025, with Oem Trivedi, he suggested dark matter might be remnants of Planck Stars left after primordial black holes evaporate. A team he led also reported tentative evidence of a black hole being born in the young nearby supernova SN 1979C.

  Life was a recurring theme. Also in 2013, working with Dan Maoz, he demonstrated that the James Webb Space Telescope could detect biomarkers such as molecular oxygen around Earth-mass planets in the habitable zones of white dwarfs. That year he also wrote about a "Habitable Epoch of the Early Universe". Around 15 million years after the Big Bang, he noted, the Cosmic Microwave Background would briefly have been warm enough for liquid water. In April 2021 he presented an updated summary of those ideas. In 2020 he published a paper on how life might travel between planets, followed by an opinion piece titled "Noah's Spaceship" about directed panspermia.

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• 4. ʻOumuamua

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  Six hours was all the time the Green Bank Telescope in West Virginia spent listening to ʻOumuamua. In December 2017, Loeb had cited the object's unusually elongated shape as a reason to try. ʻOumuamua was the first confirmed interstellar object detected in the Solar System. The SETI Institute's Allen Telescope Array had already looked without finding anything, and Green Bank detected no radio signals either.

  On the 26th of October 2018, Loeb and his postdoctoral student Shmuel Bialy submitted a paper on a stranger idea. They explored whether ʻOumuamua might be an artificial, thin solar sail pushed along by solar radiation pressure. That would help explain its non-gravitational acceleration. Other astrophysicists found the evidence insufficient, and they argued that a tumbling sail could not accelerate at all. Loeb answered with an article listing six anomalous properties that, in his view, set ʻOumuamua apart from any comet or asteroid seen before. By 2021, the scientific community broadly agreed that the object behaved like a natural body. Suggestions included an object made of nitrogen ice, or a comet-like body altered by warming on its path through the Solar System.

  On the 27th of November 2018, Loeb and Harvard undergraduate Amir Siraj proposed hunting for ʻOumuamua-like objects trapped in the Solar System after a close encounter with Jupiter. They named four candidates: 2011 SP25, 2017 RR2, 2017 SV13, and 2018 TL6. They noted that future surveys, such as one with the Large Synoptic Survey Telescope, could find many more. On the 16th of April 2019, the pair reported the discovery of a meteor of interstellar origin.

  Loeb's 2021 book Extraterrestrial: The First Sign of Intelligent Life Beyond Earth told the ʻOumuamua story for general readers. A followup, Interstellar, appeared on the 29th of August 2023. In July 2021, he went beyond writing and founded a project of his own.

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• 5. The Galileo Project

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  The Galileo Project for the Systematic Scientific Search for Evidence of Extraterrestrial Technological Artifacts began in July 2021, under Loeb's leadership. Two things inspired it: the detection of ʻOumuamua, and a report on Unidentified Aerial Phenomena from the Office of the Director of National Intelligence. The project's stated position is that science should not dismiss extraterrestrial explanations out of social stigma or cultural preference. Its statement urges researchers to "dare to look through new telescopes", both literally and figuratively.

  Three avenues of research define the effort. One is obtaining high-resolution images of Unidentified Aerial Phenomena and discovering their nature. The second is searching for ʻOumuamua-like interstellar objects. The third is looking for possible satellites built by extraterrestrial civilizations.

  The project differs from similar efforts in what it hunts. It looks for physical objects tied to extraterrestrial technology, not for electromagnetic signals. Nature, Science, The New York Post, Scientific American, and The Guardian were among the outlets that covered it.

  Some people say that studying such phenomena is pseudoscience. Loeb replies that the project does not study UFOs based on old data. He says it studies the phenomena "using the standard scientific method based on a transparent analysis of open scientific data to be collected using optimized instruments". Physical evidence also drove his most publicized expedition, which began with a fireball seen in 2014.

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• 6. The Ocean Floor Search

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  A fireball entering the atmosphere in 2014 was observed by the US Department of Defense, and it carries the catalog name CNEOS 2014-01-08. Loeb made a series of claims about it. He said the meteor came from outside the Solar System, and he estimated where it likely landed, relying partly on a seismic signal recorded around the same time. In 2023 he announced that he had found interstellar material on the ocean floor. He asserted it came from the meteor and could be remnants of an extraterrestrial starship.

  The official record was mixed. In March 2022, the U.S. Space Force affirmed that its 2014 data indicated an interstellar origin. The following month, NASA said the evidence was inconclusive.

  Scientists criticized Loeb's claims as hasty and sensational. Peter Brown, a meteor physicist at the University of Western Ontario, argued the material could be explained as non-interstellar. He noted that Defense Department measurements are opaque and prone to error. He was also disturbed by Loeb's lack of engagement with relevant experts. Monica Grady of the Open University called the evidence "rather shaky" and pointed to terrestrial pollution as more plausible. Patricio A. Gallardo, in an American Astronomical Society paper, concluded that the samples were consistent with coal ash contamination.

  Loeb responded with a preprint saying chemical analysis ruled out coal ash and indicated an extrasolar origin. With Morgan MacLeod he also proposed a tidal disruption mechanism that could eject meteors on trajectories matching the observations.

  The sharpest blow came in 2024. Planetary seismologist Benjamin Fernando led a team that reexamined the seismic signals which had directed Loeb to that patch of ocean. They concluded that one sensor had recorded a truck driving nearby, not a meteor. In their words: "Not only did they use the wrong signal, they were looking in the wrong place." A new interstellar visitor in 2025 would give Loeb another chance to make his case in public.

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• 7. 3I/ATLAS

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  In 2025, the ATLAS survey telescope in Rio Hurtado, Chile, spotted a comet approaching from the constellation of Sagittarius at interstellar velocity. ATLAS stands for Asteroid Terrestrial-impact Last Alert System, and NASA funds it. This was the third known interstellar object, and Loeb told the press it could be an alien device with potentially malevolent intent.

  He built the argument on probabilities. Speaking to Newsweek, he said: "The retrograde orbital plane of 3I/ATLAS around the Sun lies within 5 degrees of that of Earth... The likelihood for that coincidence out of all random orientations is 0.2 percent." He also said the object's brightness implied a diameter around 20 kilometers, which he called "too large for an interstellar asteroid." Its trajectory would carry it close to Venus, Mars, and Jupiter, a path he calculated at just 0.005 percent probability. "It might have targeted the inner Solar System as expected from alien technology," he added.

  Richard Moissl, Head of Planetary Defence at the European Space Agency, answered in the same outlet. He said no available observations pointed to a non-natural origin. Later observations reported water in 3I/ATLAS, a substance commonly found in comets.

  NASA officials were blunt. Nicola Fox, associate administrator of the Science Mission Directorate, said there were no technosignatures or anything else suggesting the object was other than a comet. NASA Associate Administrator Amit Kshatriya said all evidence points to a comet. Loeb conceded that 3I/ATLAS is "most likely" a comet, though he kept speculating about its supposed technological nature. The episode added to a body of criticism that had been building for years.

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• 8. Critics And Recognition

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  Steve Desch, an astrophysicist at Arizona State University, called Loeb's claims "ridiculous sensationalism" and "a real breakdown of the peer review process and the scientific method". He also warned that Loeb was polluting good science, and said several colleagues now refuse to engage with Loeb in peer review. Other scientists called the theories "nonsense", comparable to the idea that "the moon is made of cheese." USA Today described his speculation about 3I/ATLAS as an "outlandish conspiracy theory." A recurring complaint is that Loeb tends to publicize results before peer review, feeding a climate of sensationalism. On Joe Rogan's podcast he also called it a credible question whether an ancient "sophisticated civilization" existed on Earth before humanity.

  Yet his standing in the wider public sphere has been large for years. In 2006, Time magazine featured him in a cover story on the first stars, and Scientific American ran his article on the Dark Ages of the universe. In 2008, Smithsonian magazine put black holes on its cover with him, and two Astronomy magazine cover stories drew on his work. His 2011 proposal with E.L. Turner for detecting artificially-illuminated objects in the Solar System and beyond brought considerable attention. He has been interviewed by Lex Fridman, Mick West, and the H3 Podcast, among others, and The New York Times published an article about his search on the 24th of August 2023.

  Honors have accumulated alongside the controversy. He received a Guggenheim Fellowship in 2002, and Time named him among its 25 most influential people in space in 2012. That year he was also elected to the American Academy of Arts and Sciences. In 2013 the American Astronomical Society gave him the Chambliss Astronomical Writing Award for How Did the First Stars and Galaxies Form? In 2015 the Breakthrough Prize Foundation appointed him science theory director for the Breakthrough Initiatives, and in 2020 he was appointed to the President's Council of Advisors on Science and Technology. In February 2026, poet Jane Hirshfield printed a long poem about him in Poets for Science, titled The Avi Loeb Interstellar.

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