Loeb was born in
Beit Hanan, Israel, in 1962. He took part in the
Talpiot research program while serving in the
Israeli Defense Forces at age 18. While in Talpiot, he obtained a
BSc degree in physics and mathematics in 1983, an
MSc degree in physics in 1985, and a
PhD in plasma physics in 1986, all from the
Hebrew University of Jerusalem (HUJI). From 1983 to 1988, he was invited by the
U.S. Strategic Defense Initiative to work on a new
propulsion method for high-speed projectiles. Between 1988 and 1993, Loeb was a long-term member at the
Institute for Advanced Study at Princeton, where he started to work in
theoretical astrophysics under the supervision of
John Bahcall. In 1993, he moved to
Harvard University as an assistant professor in the department of
astronomy, and was
tenured three years later. Loeb has written eight books, including the textbooks
How Did the First Stars and Galaxies Form? and
The First Galaxies in the Universe. He has co-authored many papers on topics in astrophysics and cosmology, the future collision between the
Milky Way and
Andromeda galaxies, the future state of extragalactic astronomy, astrophysical implications of black hole recoil in galaxy mergers, tidal disruption of stars, and imaging black hole silhouettes. Together with his postdoc John Forbes and Howard Chen of
Northwestern University, Loeb made another prediction that sub-Neptune-sized exoplanets have been transformed into rocky
super-Earths by the activity of the black hole
Sagittarius A*. Together with Paolo Pani, Loeb showed in 2013 that primordial black holes in the range between the masses of the Moon and the Sun cannot make up
dark matter. In 2025, Loeb, in collaboration with Oem Trivedi, proposed that dark matter could consist of remnants of
Planck Stars formed after the evaporation of primordial black holes. Loeb led a team that reported tentative evidence for the birth of a black hole in the young nearby supernova
SN 1979C. In collaboration with Dan Maoz, Loeb demonstrated in 2013 that
biomarkers, such as molecular oxygen (), can be detected by the
James Webb Space Telescope (JWST) in the atmosphere of Earth-mass planets in the
habitable zone of
white dwarfs. In 2018, he served a term as chair of the board on Physics and Astronomy (BPA) of the
National Academies of Sciences, Engineering, and Medicine (NASEM).
Life in the universe In 2013, Loeb wrote about the "Habitable Epoch of the Early Universe", noting that the
Cosmic Microwave Background would temporarily have been at temperatures compatible with liquid water around 15 million years after the
Big Bang. In April 2021, he presented an updated summary of his ideas of life in the early universe. In 2020, Loeb published a paper about the possibility that life can propagate from one planet to another, followed by the opinion piece "Noah's Spaceship" about
directed panspermia.
Claims about alien life Loeb's claims about
alien life have attracted sustained criticism from other scientists. Steve Desch, an astrophysicist at
Arizona State University referred to Loeb's claims as "ridiculous sensationalism" which represent "a real breakdown of the peer review process and the scientific method". Other scientists have described Loeb's theories as "nonsense", comparable to the idea that "the moon is made of cheese." In 2024, Loeb delivered a speech in which he declared his view that the
Messiah will be an alien who arrives from outer space.
ʻOumuamua ʻOumuamua was the first confirmed interstellar object detected in the
Solar System. In December 2017, Loeb cited ʻOumuamua's unusually elongated shape as one of the reasons the
Green Bank Telescope in West Virginia should listen for
radio emissions from it to see if there were any unexpected signs that it might be of
artificial origin, although earlier limited observations by other radio telescopes such as the
SETI Institute's
Allen Telescope Array had produced no such results. The Green Bank Telescope observed the asteroid for six hours, detecting no radio signals. On October 26, 2018, Loeb and his postdoctoral student Shmuel Bialy submitted a paper exploring the possibility that ʻOumuamua is an artificial thin
solar sail accelerated by solar radiation pressure in an effort to help explain the object's non-gravitational acceleration. The consensus among other astrophysicists was that the available evidence is insufficient to consider such a premise, and that a tumbling solar sail would not be able to accelerate. In response, Loeb wrote an article detailing six anomalous properties of ʻOumuamua that make it unusual, unlike any comets or asteroids seen before. By 2021, there was widespread consensus in the scientific community that 1I/ʻOumuamua had properties entirely consistent with a naturally occurring object, perhaps made of
nitrogen ice, On November 27, 2018, Loeb and
Amir Siraj, a Harvard undergraduate, proposed a search for ʻOumuamua-like objects that might be trapped in the Solar System as a result of losing orbital energy through a close encounter with
Jupiter. They identified four candidates (
2011 SP25,
2017 RR2,
2017 SV13, and
2018 TL6) for trapped interstellar objects that dedicated missions could visit. The authors pointed out that future sky surveys, such as with
Large Synoptic Survey Telescope, could find many more. In public interviews and private communications with reporters and academic colleagues, Loeb has become more vocal about the prospects of proving the existence of alien life. On April 16, 2019, Loeb and Siraj reported the discovery of a meteor of interstellar origin.
Extraterrestrial: The First Sign of Intelligent Life Beyond Earth, a
popular science account of ʻOumuamua by Loeb, was published in 2021. A followup book,
Interstellar: The Search for Extraterrestrial Life and Our Future in the Stars, was published on August 29, 2023.
The Galileo Project to the US Congress" In July 2021, Loeb founded the Galileo Project for the Systematic Scientific Search for Evidence of Extraterrestrial Technological Artifacts. The project was inspired by the detection of ʻOumuamua and by release of the Office of the Director of
National Intelligence report on
Unidentified Aerial Phenomena (UAP). As stated on the project's website, the aim is: The three main avenues of research are: • Obtaining high-resolution images of UAPs and discovering their nature • Searching for and research of ʻOumuamua-like interstellar objects • Searching for potential ETC satellites Unlike other similar projects, the goal of the Galileo Project is to search for physical objects, and not electromagnetic signals, associated with extraterrestrial technological equipment. The project was covered by many independent publishers, among them
Nature,
Science,
The New York Post,
Scientific American,
The Guardian, etc. To allegations that
studies of UFOs is pseudoscience, Loeb answers that the project aims not to study UFOs based on previous data, but to study Unidentified Aerial Phenomena "using the standard scientific method based on a transparent analysis of open scientific data to be collected using optimized instruments".
CNEOS 2014-01-08 In 2014, the
US Department of Defense observed a fireball entering the atmosphere. all culminating in 2023, when Loeb announced that he had found
interstellar material on the ocean floor that he asserted came from the meteor and could be remnants of an
extraterrestrial starship. These claims were criticized by other scientists as hasty, sensational, and part of a pattern of improper behavior. Peter Brown, a meteor physicist at the
University of Western Ontario, argued the material can be explained as non-interstellar, noting that measurements from
Defense Department data are opaque and error-prone. Brown further said he was disturbed by Loeb's lack of engagement with relevant experts. In March 2022, the
U.S. Space Force affirmed that their 2014 data indicated an interstellar origin, while the following month
NASA stated the evidence for this was inconclusive. Astrophysicist Steve Desch, at
Arizona State University, commented "[Loeb's claims are] polluting good science—conflating the good science we do with this ridiculous sensationalism and sucking all the oxygen out of the room", and said several of his colleagues are consequently refusing to engage with Loeb in the
peer review process. Loeb subsequently authored a preprint saying chemical analysis ruled out coal ash contamination and indicated extrasolar origins. Loeb and Morgan MacLeod proposed a tidal disruption mechanism that could cause meteors to be ejected into trajectories leading to the described observations. In 2024 planetary seismologist Benjamin Fernando led a team that analyzed the seismic signals that led Loeb to search that specific region of the ocean, and they concluded that the seismic signals from one of the sensors used was in fact caused not by a meteor, but by a truck driving near the sensor, so that, "Not only did they use the wrong signal, they were looking in the wrong place."
3I/ATLAS In 2025, ATLAS (Asteroid Terrestrial-impact Last Alert System), the NASA-funded survey telescope in
Rio Hurtado, Chile, observed a comet approaching from the constellation of
Sagittarius at an interstellar velocity. Loeb hypothesized in the press that this, the third known interstellar object, could be an alien device with potentially malevolent intent. He based these speculations on his calculations of the likelihood of a comet of natural origins having these characteristics. "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," Loeb told
Newsweek. He further claimed that the brightness of 3I/ATLAS implies an object that is around 20 kilometers in diameter which is "too large for an interstellar asteroid." 3I/ATLAS' trajectory will bring it close to Venus, Mars and Jupiter, a path Loeb calculated as having a probability of just 0.005 percent. "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 told Newsweek: "There have been no signs pointing to non-natural origins of 3I/ATLAS in the available observations." Since then, observations have reported evidence of 3I/ATLAS containing water, which is a substance commonly found in comets. Independent assessments have resoundingly rejected the idea that 3I/ATLAS is anything except a comet.
Nicola Fox, associate administrator of NASA's
Science Mission Directorate said that "We certainly haven't seen any technosignatures or anything from it that would lead us to believe it was anything other than a comet". Similarly, NASA Associate Administrator
Amit Kshatriya stated that "all evidence points to it being a comet." == Media appearances ==