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Mitch Begelman

Mitch Begelman decided he wanted to be an astrophysicist when he was five years old and living in the Bronx, New York, with his parents Irving and Barbara. In 1958, he saw a Walt Disney program about interplanetary space travel and immediately knew science was for him. To his delight, his parents gave him a small refracting telescope for his 6th birthday in March of 1959. He soon became an active amateur astronomer.

Begelman was an observational astronomer through high school. His astronomy club used to rent a cottage in the Catskills, and that was where he did most of his observing. He also used to observe from the roof of his family’s 6-story apartment building in the Bronx, which was on a major street called the Grand Concourse. He saw the Aurora Borealis for the first time from the Grand Concourse.

During junior high and later at the Bronx High School of Science, he was involved in the Amateur Astronomers Association of New York, which was then based in the old Hayden Planetarium in the Museum of Natural History in New York City. He served as the Deep Sky Recorder and later as the Planetary Recorder. This group met monthly, but older people dominated those meetings. However, Begelman was also active in the Amateur Observers Society of New York, based in Queens. The Amateur Observers Society was entirely composed of high school students.

Begelman remembers those days fondly. He and his friends organized expeditions. They once got the 86th floor observation deck of the Empire State Building all night to observe a lunar eclipse. One memorable daytime observation was the transit of Mercury across the Sun. The group even had its picture taken and displayed on the cover of the (New York) Daily News and the New York Post. The amateur astronomers also organized a trip to North Carolina to view a total eclipse of the Sun in March of 1970. This expedition is the only solar eclipse ever successfully viewed by Begelman.

Begelman was one of the first people to earn a Messier Club certificate from the Astronomical League for personally observing all the Messier objects in the sky. There are about 110 of these fuzzy-looking, immobile objects in the sky. Messier catalogued them as a way of warning people not to waste their time looking at them if they wanted to discover comets, which move across the sky.

Begelman, of course, was fascinated by the Messier objects, which are a mixture of galaxies, clusters of stars, and nebulae. M1, for example, is the Crab Nebula, which Begelman observed many times with his telescope (by then upgraded to a 6-in reflector) during high school. Not surprisingly—for a man who ponders the same questions through many decades—the Crab Nebula has been the subject of at least a dozen papers written by Begelman and colleagues in the University of Colorado, including six in the past three years,  aimed at  explaining important new gamma-ray discoveries.

When Begelman went to Harvard in 1970, he decided to major in physics. Most of the time he was there, he didn’t know what kind of physics he wanted to specialize in. Not surprisingly, however, in his last year, he decided to go into astrophysics after completing some interesting undergraduate research on (1) spinning magnetized dust grains in interstellar space and (2) the atmosphere of Venus. Begelman graduated from Harvard in 1974 with Bachelor’s and Master’s degrees in physics. Next, he started graduate school at the University of Cambridge, concentrating in theoretical astrophysics.

At Cambridge, he went to work with Martin Rees, a young professor studying quasars, cosmology, and black holes. Begelman decided to work on black holes, which was a somewhat risky choice in the mid-1970s because most people still didn’t believe black holes actually existed. Begelman and Rees decided to see if they could explain the phenomena being observed that supported the idea of black holes, but without having a black hole. The goal was to see if they could rule out all the alternative explanations.

One of the biggest surprises of that time was the discovery of cosmic jets. No one expected black holes to eject much of the gas in their vicinity. Begelman worked on some of the early papers that attempted to understand the physics of jets, including one he co-authored with Roger Blandford and Rees  in 1984 on the physics of jets, which remains his single most highly cited paper. He still explores the physics of jets.

Begelman’s early explorations of black holes in graduate school led to decades of studies of black holes and a popular book on black holes entitled Gravity’s Fatal Attraction: Black Holes in the Universe, jointly authored by Begelman and Rees. The book’s first edition was published in 1996 and its second edition in 2009. He won the American Institute of Physics Science Writing Award for the first edition of the book.

He also authored Turn Right at Orion, a fictional memoir of what it would be like to travel around the Milky Way looking at weird objects, and then to fly to the Virgo Cluster to visit M87, a supergiant elliptical galaxy. Begelman has always enjoyed his popular science writing projects.

Begelman has many research interests in addition to black holes and jets. He studies interstellar and intergalactic gas, the interactions of very energetic particles (cosmic rays) with gas, and other topics exploring the physics of matter in very low-density areas between stars and between galaxies. This work, together with his explorations of the physics of black holes, is much easier today with the availability of supercomputers containing tens of thousands of processors running in parallel, capable of performing  250-years worth of simulation in a single day.

Though he has studied many other topics in astrophysics, Begelman is frequently drawn back into investigations of black holes. He finds it fascinating to explore a topic where so much is speculative and it’s possible to dream about all sorts of processes that may occur, even though observational verification may be far in the future. He is quick to point out, however, that a surprising number of these seemingly wild speculations have ultimately received observational support.

A question he is currently asking is: how close to the speed of light can a jet of gas really get? Right now, no one knows what determines the speeds of jets. However, Begelman has a novel approach to solving this problem. He thinks that the jets whose speeds approach the speed of light are the ones that are not driven by magnetic fields. There’s a reason he believes this even though he’s about the only one who does. The reason is that if there’s a magnetic field in a gas with very high speed, the magnetic field automatically generates an electric field because of induction. And, the electric field develops forces that are almost exactly equal and opposite to the forces of the magnetic field. Thus it’s very hard to accelerate ionized gas beyond some large fraction of the speed of light. Consequently, the less acceleration depends on magnetic fields, the easier it is to attain ultra high speeds. And, Begelman hypothesizes that’s exactly what propulsion by radiation pressure—rather than magnetic fields—can accomplish in extreme environments.

Another novel investigation of his is the Zero-Bernoulli accretion flows, or ZEBRAs. A ZEBRA can form out of the debris from a star being sucked into a black hole. Depending on the angular momentum of the debris, accretion “disks” around black holes can form three-dimensional spheres with a jet coming out of a hole in their top. The stellar-like objects with a black hole (or neutron star) in the center are ZEBRAs. There may be other circumstances in extreme environments where ZEBRAs form as well.

Begelman is most attracted to the study of extreme phenomena such as ZEBRAs, jets, and black holes. He likes to investigate things in the Universe that are so far from what you see on Earth that a person has to use all the powers of his or her imagination as well as mathematics to understand what’s going on. In other words, he jumps into topics where scientists just barely know what the relevant physics might even be. In the end, he loves to ask questions, especially questions no one else has thought of yet. He prefers coming at problems from creative new directions as well.

Begelman is currently Chair of the Department of Astrophysical and Planetary Sciences at the University of Colorado. He has given decades of professional service to such organizations as NASA, the American Astronomical Society, and the National Science Foundation. He has also won numerous honors and awards, including a Presidential Young Investigator Award in 1984, an Alfred P. Sloan Foundation Research Fellowship in 1987, and the Helen B. Warner Prize of the American Astronomical Society in 1988. He received University of Colorado Faculty Fellowships in 1990–1991, 1998–1999, and 2005–2006. He won a Guggenheim Fellowship in 1998–1999 and a Boulder Faculty Assembly Award for Excellence in Research, Scholarly, and Creative Work in 1999–2000. He was the first Boldt Lecturer at the NASA/Goddard Space Flight Center in 2004 and a Visiting Fellow Commoner at Trinity College, Cambridge in 2005–2006. He is a Fellow of the Royal Astronomical Society and the Cambridge Philosophical Society. 

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