Photograph: Jacob Shaham.
Jacob Shaham, among the world's leading theoretical astrophysicists in the study of neutron stars and professor of physics at Columbia, died of heart failure Apr. 20 at Presbyterian Hospital after a brief illness. He was 52 and lived in Riverdale in the Bronx.
"He has made landmark contributions to our knowledge of pulsars and neutron stars" and other areas of astrophysics, said Malvin A. Ruderman, Centennial Professor of Physics at Columbia. Shaham and his collaborators explained why neutron stars periodically increase their rate of spin and why oscillations in their radio frequencies are often observed. A team of Columbia physicists of which he was a part predicted that pulsars that evaporated companion stars would be found, a prediction that was almost immediately confirmed.
Neutron stars are extremely dense objects, with the mass of the sun packed into a diameter of perhaps 10 kilometers; they are thought to result when normal stars collapse in supernova explosions. Rotating neutron stars emit periodic electromagnetic radiation and are also known as pulsars.
He studied quasiperiodic oscillations in the timing and intensity of X-ray emissions from spinning neutron stars. Such X-rays are emitted when neutron stars pull matter away from companion stars. He proposed that the pulsing radiation was much like the regular beat produced when two tuning forks of slightly different frequencies are struck next to one another. In neutron star systems, the two sources of X-rays of slightly different frequencies were the rapid, planetlike orbits of the accreting matter and the rotation of the neutron star, he said.
Certain pulsars appear to have increased their rate of spin over time, and in 1983 Ruderman and Shaham predicted that such millisecond pulsars increased their spin by accreting mass from a companion star. In 1988, a team of Columbia astrophysicists that included Ruderman and Shaham, as well as Marco Tavani, proposed the mechanism by which this accretion would take place, and predicted that such pulsars would eventually evaporate their companion stars. Almost simultaneously, a team of Princeton astronomers discovered PSR B1957+20, a neutron star that was in the process of devouring its companion. Astronomers quickly dubbed this object the "Black Widow Pulsar."
In a paper presented to the American Astronomical Society in Minneapolis on May 30, 1994, Shaham and a colleague, James H. Applegate, associate professor of astronomy at Columbia, developed a theory that explained many properties of this system. They proposed that a constant battle between two forces--the pulsar's hot solar wind blowing matter away from the companion, and the pulsar's huge gravitational force--created enough friction to heat the dying companion star internally, expanding it to twice its expected size and generating higher luminosity than expected. Such tidal energies had never before been observed in stars.
Born Jacob Bronstein in Tel Aviv in 1942, Shaham received the B.Sc. degree summa cum laude in 1963 and the M.Sc. summa cum laude in 1965, both from Hebrew University, Jerusalem. After serving in the Israeli Army from 1965 to 1968, he returned to Hebrew University and received the Ph.D. in 1971.
Though his first scientific interest was condensed matter physics, the study of solids at the atomic level, with the discovery of neutron stars in the late 1960s Shaham took up the discipline of astrophysics. He conducted research with David Pines, professor of physics at the University of Illinois at Urbana-Champaign, from 1970 to 1973, then returned to Hebrew University to take a series of positions at the Racah Institute of Physics.
Shaham interviewed leading scientists and explained their work on "Tatzpit" ("Observation"), a weekly television program he created on Israeli Television in the early 1980s. The program made him known to the entire country.
>From 1982 to 1984, while on sabbatical from Hebrew University, he was a visiting professor and Ernest Kempton Adams Fellow at Columbia. In 1984, he was appointed professor of physics with tenure at Columbia. He also served as member of the Academic Senate and chairman of the physics graduate and undergraduate committees. In 1994, he was appointed deputy chairman of Columbia's physics department and co-director of the Columbia Astrophysics Laboratory.
Shaham was a popular teacher among both graduate and undergraduate students. He taught Quantum Mechanics and Physics in Practice, a course on how physicists come to understand and solve problems. "He was truly inspirational," said Norman H. Christ, professor and chairman of the physics department at Columbia.
Among Shaham's grants and awards were the G. Racah Memorial Fellowship at Hebrew University, 1966-67 and a Senior Fulbright-Hays Travel Grant for postdoctoral work, 1970-73. He was a member of the International High Energy Astrophysics Committee of the International Astronomical Union, 1976-1979. He reviewed scientific papers for Nature, The Astrophysical Journal, Astronomy and Astrophysics, The Physical Review and Nuclear Physics, as well as for the National Science Foundation and the National Aeronautics and Space Administration.
He lectured at numerous scientific meetings both in the United States and abroad, and is the author or coauthor of more than 100 scientific papers and a dozen books.
Shaham met the former Meira Diskin while both were doctoral students at Hebrew University. They were married in the university's campus synagogue in 1965. Meira Shaham, who holds a Ph.D. in human genetics from Hebrew University, is a cytogeneticist and directs a private laboratory in Westchester , N.Y.
When the couple's first child was born in 1968, they changed the family name from Bronstein to Shaham, following a popular Israeli practice of translating surnames from European languages to Hebrew. "Bronstein" is "brown stone" in German, Meira Shaham said, while "shaham" is Hebrew for a brown stone found in Israel. "Jacob Shaham was as remarkable a father as he was a scientist," said Pines.
He is also survived by two sons, Shai and Gil, and a daughter, Orli, all of New York City. Shai was valedictorian of the Class of 1989 at Columbia College and has recently completed work for a Ph.D. is molecular genetics at MIT. Gil attended Columbia from 1989 to 1990 and is an internationally recognized concert violinist. Orli, an honor student in her sophomore year at Columbia, is a concert pianist. Interment will be in Israel. A memorial service will be held in St. Paul's Chapel on Thurs., May 4.