Walter Lewin

Walter Hendrik Gustav Lewin (The Hague, January 29, 1936) is a Dutch astrophysicist and retired professor of physics at the Massachusetts Institute of Technology.

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.

His paternal grandparents Gustav and Emma Lewin, who were Jewish, died in Auschwitz in 1942.

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.

Lewin earned his doctorate in nuclear physics in 1965 at the Delft University of Technology and was a member of MIT's physics faculty for 43 years beginning in 1966 until his retirement in 2009.

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.

Walter Lewin taught high school physics while studying for his PhD, then he went to Massachusetts Institute of Technology in January 1966 as a post-doctoral associate, and was appointed an assistant professor.

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.

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 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).

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.

He was promoted to associate professor of physics in 1968 and to full professor in 1974.

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.

Lewin collaborated with his close friend Jan van Paradijs of the University of Amsterdam from 1978 until van Paradijs' death.

They co-authored 150 papers.

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.

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.

He became a corresponding member of the Royal Netherlands Academy of Arts and Sciences in 1993 and a fellow of the American Physical Society in 1993.

Lewin and graduate student Jeffrey Kommers have worked on data from the Compton Gamma Ray Observatory (GRO).

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.