Lewin's contributions in astrophysics include the first discovery of a rotating neutron star through all-sky balloon surveys and research in X-ray detection in investigations through satellites and observatories. Lewin has received awards for teaching and is known for his lectures on physics and their publication online via YouTube, MIT OpenCourseWare and edX.
In December 2014, MIT revoked Lewin's Professor Emeritus title after an MIT investigation determined that Lewin had violated university policy by sexually harassing an online student in a MITx course he taught in fall 2013.[1][2][3]
Lewin was born to Walter Simon Lewin and Pieternella Johanna van der Tang in 1936 in The Hague, Netherlands. He was a child when Nazi Germany occupied The Netherlands during World War II.[4] His paternal grandparents Gustav and Emma Lewin, who were Jewish, died in Auschwitz in 1942.[5][6] To protect the family, Lewin’s father — who was Jewish, unlike his mother — decided one day to simply leave without telling anyone. His mother was left to raise the children and run a small school she and her husband had started together. After the war ended, his father resurfaced; Lewin describes having a “more or less normal childhood.” His parents continued running the school, which he says strongly influenced his love of teaching.[4][7]
At MIT, Lewin joined the X-ray astronomy group and conducted all-sky balloon surveys with George W. Clark. Through the late seventies, there were about twenty successful balloon flights. These balloon surveys led to the discovery of five new X-ray sources, whose spectra were very different from the X-ray sources discovered during rocket observations. The X-ray flux of these sources was variable. Among them was GX 1+4 whose X-ray flux appeared to be periodic with a period of about 2.4 minutes. This was the first discovery of a slowly rotating neutron star.[9]
In October 1967 when Scorpius X-1 was observed, an X-ray flare was detected. The flux went up by a factor of about 4 in ten minutes after which it declined again. This was the first detection of X-ray variability observed during the observations. The rockets used by other researchers could not have discovered that the X-ray sources varied on such short time scales because they were only up for several minutes, whereas the balloons could be in the air for many hours.[10]
Lewin was co-investigator on the Small Astronomy Satellite 3 (SAS-3) project. He directed the burst observations and discovered several X-ray bursters, among them was the rapid burster[11] which can produce thousands of X-ray bursts in one day. His group also discovered that the rapid burster produces two types of bursts and established a classification of bursts as type I (thermonuclear flashes) and type II (accretion flow instabilities).[12]
Lewin was co-principal investigator on High Energy Astronomy Observatory 1 HEAO-1 (A4), which has yielded the first all sky catalog at high-energy X rays. With H. Pedersen and J. van Paradijs, Lewin made extensive studies of optical bursts which are associated with X-ray bursts; for X-ray detections they used SAS-3 and the Japanese observatory "Hakucho". Their combined burst observations demonstrated that the optical bursts are a few seconds delayed relative to the X-ray bursts. This established the size of the accretion disc surrounding the accreting neutron stars.
In his search for millisecond X-ray pulsations from low-mass X-ray binaries, in 1984–85 Lewin made guest observations with the European observatory EXOSAT in collaboration with colleagues from Amsterdam and Garching, Germany. This led to the unexpected discovery of intensity-dependent quasi-periodic oscillations (QPO) in the X-ray flux of GX 5-1. During 1989 to 1992, using the Japanese observatory "Ginga", Lewin and his co-workers studied the relation between the X-ray spectral state and the radio brightness of several bright low-mass X-ray binaries.[13]
Lewin was closely involved in ROSAT observations of the nearby galaxies M31 and Messier 81. Lewin and his graduate student Eugene Magnier have made deep optical charge-coupled device observations of M31 in four colors; they have published a catalogue of 500,000 objects. Lewin and his graduate student David Pooley initiated the successful X-ray observations within six days of the appearance of supernova SN 1993J in M81.
Lewin and graduate student Jeffrey Kommers have worked on data from the Compton Gamma Ray Observatory (GRO). This was a collaboration with the BATSE Group[17] in Huntsville, AL. In early December 1995, with co-workers Chryssa Kouveliotou and Van Paradijs, they discovered a new type of X-ray burst source: (GRO J1744-28) the Bursting Pulsar, and received a NASA Achievement Award for this discovery.
In 1996–1998, Lewin's collaboration with Michiel van der Klis in Amsterdam led to the discovery of kHz oscillations in many X-ray binaries.
2003 – MIT Everett Moore Baker Memorial Award for Excellence in Undergraduate Teaching[20]
2011 – first recipient of the Educator Award for OpenCourseWare Excellence (ACE)[21]
On April 3, 2012, Lewin was ranked by the Princeton Review among "The Best 300". He was the only MIT faculty member (albeit, retired) to make it to that list.[22][23]
For about 15 years (starting in 1982) Lewin presented a one-hour program weekly on MIT Cable TV. The shows were aired 24 hours per day helping freshmen with their weekly homework assignments. Videos of Lewin's lectures on Newtonian mechanics (1999), electricity and magnetism (2002) and the physics of vibrations and waves (2004), among others, could be viewed on the MIT OpenCourseWare web site until MIT removed them after finding that Lewin had sexually harassed a student in the online course.[3]
Since February 2015, Lewin has been running and managing his own YouTube channel called "Lectures by Walter Lewin. They will make you ♥ Physics".[24] Several of his lectures have been viewed more than a million times. His 2011 farewell lecture "For the Love of Physics" has been viewed around 15 million times - 1 million times on MIT's OCW, 6.9 million times on the channel "For the Allure of Physics" [25] and 6.9 million times on his personal channel.[26] In 2007, The New York Times featured Lewin on the front page, talking about his influence on online education.[27]
In the summer of 2012, Lewin returned from his retirement to deliver a lecture series initiated and funded by the Japanese Broadcasting Corporation (NHK).[28] Each lecture features a selection of physics demonstrations that Lewin has used in his lectures at MIT. The lectures consist of eight TV programs that were broadcast in Japanese on NHK in Japan in 2013. As of 2015, a region 2 DVD box set of this series is available in Japanese, with an optional partial English audio track and English subtitles.[29]
In early December 2014, MIT determined that Lewin had sexually harassed an online MITx learner, in violation of MIT's policies.[1]Inside Higher Ed reported that this learner was one of at least 10 female students to whom Lewin had sent inappropriate messages.[30] The victim, a 32-year-old woman living in France, said that she came forward to ensure that the case was not forgotten, stating that Lewin pushed her to participate in sexual role-playing.[30] As a consequence of its internal investigation, MIT revoked Lewin's professor emeritus title,[2] and removed his lectures from the institute's online learning platforms.[31]
Lewin, Walter; van der Klis, Michiel, eds. (2006). Compact stellar X-ray sources. Cambridge University Press. ISBN978-0-521-82659-4.
Lewin, Walter H.G.; van Paradijs, Jan; van den Heuvel, Edward P.J., eds. (1995). X-ray binaries. Cambridge University Press. ISBN978-0-521-41684-9.
Truemper, J.; Lewin, W.H.G.; Brinkmann, W., eds. (1986). The evolution of galactic X-ray binaries. D. Reidel Pub. Co.; Sold and distributed in the U.S.A. and Canada by Kluwer Academic Publishers. ISBN978-90-277-2184-6.
Lewin, Walter H.G.; van den Heuvel, Edward, eds. (1983). Accretion-driven stellar X-ray sources. Cambridge University Press. ISBN0-521-24521-4.
J. Miller; A. Fabian; R. Wijnands; R. Remillard; P. Wojdowski; N. Schulz; et al. (2002). "Resolving the Composite Fe K-alpha Emission Line in the Galactic Black Hole Cygnus X-1 with Chandra". Astrophysical Journal. 578 (1): 348–356. arXiv:astro-ph/0202083. Bibcode:2002ApJ...578..348M. doi:10.1086/342466. S2CID119393282.
D. Pooley; W. Lewin; L. Homer; S. Anderson; B. Gaensler; B. Margon; et al. (2002). "Optical Identifications of Multiple Faint X-ray Sources in the Globular Cluster NGC~6752: Evidence for Numerous Cataclysmic Variables". Astrophysical Journal. 569 (1): 405. arXiv:astro-ph/0110192. Bibcode:2002ApJ...569..405P. doi:10.1086/339210. S2CID12626024.
^Lewin, Walter H. G.; Ricker, George R.; McClintock, Jeffrey E. (October 1971). "X-Rays from a New Variable Source GX 1+4". Astrophysical Journal. 169: L17. Bibcode:1971ApJ...169L..17L. doi:10.1086/180805.
^Lewin, Walter H. G.; McClintock, Jeffrey E.; Ryckman, Stanley G.; Glass, Ian S.; Smith, William B. (November 1970). "Continual Variations in the High-Energy Flux of X-Rays from Scorpius X-1". Astrophysical Journal. 162: L109. Bibcode:1970ApJ...162L.109L. doi:10.1086/180635.
^Lewin, Walter H. G.; Van Paradijs, J.; Van Der Klis, M. (1991). "Quasi-periodic oscillations in low-mass X ray binaries". NAS-NRC, High-Energy Astrophysics. American and Soviet Perspectives: 251. Bibcode:1991heaa.conf..251L.
^Walter H. G. Lewin (2003). Edward P. van den Heuvel; Lex Kaper; Evert Rol; Ralph A.M.J. Wijers (eds.). My Quarter Century with Jan. ASP Conference Proceedings. Vol. 308. p. 27. arXiv:astro-ph/0105344. Bibcode:2003ASPC..308...27L.
^"Walter Lewin". Royal Netherlands Academy of Arts and Sciences. Archived from the original on 20 July 2015. Retrieved 17 July 2015.
^Pooley, David; Lewin, Walter H. G.; Verbunt, Frank; Homer, Lee; Margon, Bruce; Gaensler, Bryan M.; Kaspi, Victoria M.; Miller, Jon M.; Fox, Derek W. (28 March 2002). "Chandra Observation of the Globular Cluster NGC 6440 and the Nature of Cluster X-ray Luminosity Functions". The Astrophysical Journal. 573 (1): 184–190. arXiv:astro-ph/0111212. Bibcode:2002ApJ...573..184P. doi:10.1086/340498. ISSN0004-637X. S2CID119401055.