Avi Loeb


Abraham "Avi" Loeb is an American theoretical physicist who works on astrophysics and cosmology. Loeb is the Frank B. Baird Jr. Professor of Science at Harvard University. He serves as Chair of the Harvard Astronomy department, Chair of the Advisory Committee for the Breakthrough Starshot project – which aims to launch lightweight spacecraft towards the nearest stars using a powerful laser, founding director of Harvard's Black Hole Initiative – the first interdisciplinary center worldwide dedicated to the study of black holes, and director of the Institute for Theory and Computation within the Harvard-Smithsonian Center for Astrophysics.
Loeb is an elected fellow of the American Academy of Arts and Sciences, the American Physical Society, and the International Academy of Astronautics. In July 2018 he was appointed as chair of the Board on Physics and Astronomy of the National Academies, which is the Academies' principal forum for issues connected with the fields of Physics and Astronomy including oversight of their decadal surveys. In June 2020 Loeb was sworn in as a member of the President's Council of Advisors on Science and Technology at the White House. In December 2012, TIME magazine selected Loeb as one of the 25 most influential people in space. In 2015, Loeb was appointed as the Science Theory Director for the Breakthrough Initiatives of the Breakthrough Prize Foundation. In 2018, he attracted media attention for suggesting that alien space craft may be in our solar system, using the anomalous behavior of 'Oumuamua as an example. In 2019, Loeb reported together with his Harvard undergraduate student, Amir Siraj, the first discovery of a meteor that originated outside the Solar System.

Career

Loeb was born in Beit Hanan, Israel in 1962 and took part in the national Talpiot program before receiving a graduate degree in plasma physics at age 24 from the Hebrew University in Jerusalem. Between 1988 and 1993, Loeb was a long-term member at the Institute for Advanced Study in Princeton, where he started to work in theoretical astrophysics. In 1993, he moved to Harvard University as an assistant professor in the department of astronomy, where he was tenured three years later.
Loeb has published nearly seven hundred papers on a broad range of research areas in astrophysics and cosmology, including the first stars, the epoch of reionization, the formation and evolution of massive black holes, the search for extraterrestrial life, gravitational lensing by planets, gamma-ray bursts at high redshifts, 21-cm cosmology, the use of the Lyman-alpha forest to measure the acceleration/deceleration of the universe in real time, 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. Some of his papers are considered as pioneering in areas that have become by now the focus of established communities of astrophysicists.
Several of Loeb's early predictions were confirmed in recent years. In 1992, he suggested with Andy Gould that exoplanets could be detected through gravitational microlensing, a technique that is routinely used these days. In 1993, he proposed the use of the C+ fine-structure line to discover galaxies at high redshifts, as done routinely now. In 2005, he predicted in a series of papers with his postdoc at the time, Avery Broderick, how a hot spot in orbit around a black hole would appear; their predictions were confirmed in 2018 by the GRAVITY instrument on the VLT which observed a circular motion of the centroid of light of the black hole at the center of the Milky Way, SgrA*. In 2009, Broderick and Loeb predicted the shadow of the black hole in the giant elliptical galaxy M87, which was imaged in 2019 by the Event Horizon Telescope. In 2013, a report was published on the discovery of the "Einstein Planet" Kepler 76b, the first Jupiter size exoplanet identified through the detection of relativistic beaming of its parent star, based on a technique proposed by Loeb and Gaudi in 2003. In addition, a pulsar was discovered around the supermassive black hole, SgrA*, following a prediction by Pfahl and Loeb in 2004.
Also, a hypervelocity star candidate from the Andromeda galaxy was discovered, as predicted by Sherwin, Loeb, and O'Leary in 2008.
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 the dark matter, another result reported in TIME magazine.
He led a team that discovered tentative evidence for the birth of a black hole in the young nearby supernova SN1979C.
In collaboration with Dan Maoz, Loeb demonstrated in 2013 that biomarkers, such as molecular oxygen, can be detected by the James Webb Space Telescope over the next decade in the atmosphere of Earth-mass planets in the habitable zone of white dwarfs.
Together with his postdoc, James Guillochon, Loeb predicted the existence of a new population of stars moving near the speed of light throughout the universe. 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 Milky Way's central supermassive black-hole Sagittarius A*.

Early Universe

Loeb was among the very first theorists to trigger the research frontier on the "cosmic dawn" of the first stars and galaxies. In a series of papers with his students and postdocs, he addressed how and when the first stars and black holes formed and what effects they had on the young universe.
Together with his former student Steve Furlanetto, Loeb published in December 2012 an extensive textbook entitled "The First Galaxies in the Universe".
In 2013, Loeb introduced the new concept of "The Habitable Epoch of the Early Universe", and mentored Harvard undergraduate, Henry Lin, in the study of industrial pollution on exoplanets as a new method to search for extraterrestrial civilizations.

ʻOumuamua

In December 2017, Loeb cited ʻOumuamua's unusually elongated shape as one of the reasons why the Green Bank Telescope in West Virginia would 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. On 13 December 2017, the Green Bank Telescope observed the asteroid for six hours across four bands of radio frequency. No radio signals from ʻOumuamua were detected in this very limited scanning range, but observations are ongoing.
On 26 October 2018, Loeb and his postdoc Shmuel Bialy submitted a paper exploring the possibility of the interstellar object ʻOumuamua being an artificial thin solar sail accelerated by solar radiation pressure in an effort to help explain the object's non-gravitational acceleration. Other scientists have stated 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 `Oumuamua that make it unusual, unlike any comets or asteroids seen before.
On 27 November 2018, Loeb and his undergraduate student at Harvard College, Amir Siraj, proposed a search for `Oumuamua-like objects which are trapped in the Solar System as a result of losing orbital energy through a close encounter with Jupiter. They identified 4 candidates for trapped interstellar objects that could be visited by dedicated missions. The authors pointed out that future sky surveys, such as with LSST, should find many more.
In public interviews and private communications with reporters and academic colleagues, Loeb has become increasingly vocal regarding the prospects of proving the existence of alien life.
On April 16, 2019, Loeb and his undergraduate student, Amir Siraj, reported the discovery of the first meteor of interstellar origin. This discovery pioneers a new path for studying the composition and nature of interstellar objects.
Loeb is completing a popular-level book titled "Extraterrestrial" to be published by HMH on January 26, 2021, with translations to more than twenty languages. He also co-authors a textbook on "Life in the Cosmos: From Bio-Signatures to Techno-Signatures" with his former postdoc, Manasvi Lingam, to be published in 2021 by Harvard University Press.

Media appearances

In 2006, Loeb was featured in a cover story of TIME magazine on the first stars and in a Scientific American article on the Dark Ages of the universe. In 2008, he was featured in a cover story of Smithsonian magazine on black holes and in two cover stories of Astronomy Magazine, one on the collision between the Milky Way and the Andromeda Galaxy and the second on the future state of our universe. In 2009, Loeb reviewed in a Scientific American article a new technique for imaging black hole silhouettes. In 2010 he wrote a textbook entitled "How Did the First Stars and Galaxies Form?", published by Princeton University Press. In the same year, Loeb wrote an article encouraging young researchers to be creative. Loeb received considerable media attention after proposing in 2011 a new technique for detecting artificially-illuminated objects in the Solar System and beyond, and showing in 2012 that planets may transit hypervelocity stars or get kicked to a fraction of the speed of light near the black hole at the center of the Milky Way.
Science magazine published a detailed article about Loeb's career in April 2013, and Discover magazine reviewed his pioneering research on the first stars in April 2014. The New York Times published a science profile of Loeb in December 2014. In May 2015, Astronomy magazine posted a podcast of an hour-long interview with Loeb in its series entitled "Superstars of Astronomy". In April 2016, Stephen Hawking visited Loeb's home and attended the inaugurations of the Starshot and Black Hole Initiatives that Loeb leads.
Loeb's latest eBook on Kindle details his career path from childhood on a farm with interests in philosophy to chairing the Harvard Astronomy department and directing the ITC, and includes opinion essays on the importance of taking risks in research and promoting diversity. Loeb regularly writes timely opinion essays on science and policy.

Honors and awards

Loeb has received many honors, including the Kennedy Prize in 1987, the Guggenheim Fellowship in 2002, the Salpeter Lectureship at Cornell University in 2006, the Bahcall Lectureship at Tel Aviv University in 2006, the Merle Kingsley Lectureship at Caltech in 2007, the Australian Institute of Physics Lectureship at the University of Melbourne in 2007, the Distinguished Visiting Lectureship at the Carnegie Observatories in 2009, the Las Cumbres Observatory Lectureship at Santa Barbara in 2011, the Sackler Lectureship at Leiden Observatory in 2011, the Galileo Galilei Chair for 2011–12 from Scuola Normale Superiore in Pisa, Italy, and the Miegunyah Distinguished Visiting Fellowship for 2013 at the University of Melbourne in Australia.
For over two decades he held a visiting professorship at the Weizmann Institute of Science, and since 2011 he was awarded a Sackler Professorship by special appointment in the School of Physics and Astronomy at Tel Aviv University. In 2012 Loeb was elected as a member of the American Academy of Arts and Sciences. In 2013, he was awarded the Chambliss Astronomical Writing Award by the American Astronomical Society for the book he published in 2010.