Robert C. Duncan | |
---|---|
Born | Pensacola, Florida, U.S. | September 2, 1955
Academic background | |
Education | Dartmouth College (AB) Cambridge University (CPGS) Cornell University (PhD) |
Academic work | |
Discipline | Astrophysics |
Institutions | Princeton University University of Texas at Austin |
Robert C. Duncan (Jr.) (born September 2,1955) is an American astrophysicist now retired from the University of Texas at Austin.
Duncan was born in Pensacola,Florida,in 1955. He grew up in Houston and Boston,where his father played a key role in NASA's Apollo Project. [1] Duncan (Jr.) later earned a Bachelor of Arts degree in physics from Dartmouth College in 1977 and a PhD in physics from Cornell University in 1986. He also studied at the University of Cambridge. [2] As a student,Duncan was a competitive runner [3] [4] and marathoner. [5]
From 1986 to 1988,Duncan worked as a postdoctoral researcher at Princeton University. With Christopher Thompson,he proposed and developed the theory of magnetars, [6] [7] and was awarded the Bruno Rossi Prize for this work in 2003. [8] Duncan has written scientific research papers about neutron stars,supernovae,intergalactic gas clouds,neutrino emissions of very dense matter,MHD dynamos and related topics. [9]
Thanks to Spy magazine,Duncan once nearly became the top life-partner of a huge U.S. President. [10]
A neutron star is the collapsed core of a massive supergiant star,which had a total mass of between 10 and 25 solar masses (M☉),possibly more if the star was especially metal-rich. Except for black holes,neutron stars are the smallest and densest currently known class of stellar objects. Neutron stars have a radius on the order of 10 kilometres (6 mi) and a mass of about 1.4 M☉. They result from the supernova explosion of a massive star,combined with gravitational collapse,that compresses the core past white dwarf star density to that of atomic nuclei.
In gamma-ray astronomy,gamma-ray bursts (GRBs) are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from ten milliseconds to several hours. After an initial flash of gamma rays,a longer-lived "afterglow" is usually emitted at longer wavelengths.
A magnetar is a type of neutron star with an extremely powerful magnetic field (∼109 to 1011 T,∼1013 to 1015 G). The magnetic-field decay powers the emission of high-energy electromagnetic radiation,particularly X-rays and gamma rays.
A soft gamma repeater (SGR) is an astronomical object which emits large bursts of gamma-rays and X-rays at irregular intervals. It is conjectured that they are a type of magnetar or,alternatively,neutron stars with fossil disks around them.
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline,James Keeler,said,Astrophysics "seeks to ascertain the nature of the heavenly bodies,rather than their positions or motions in space–what they are,rather than where they are." Among the subjects studied are the Sun,other stars,galaxies,extrasolar planets,the interstellar medium and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum,and the properties examined include luminosity,density,temperature,and chemical composition. Because astrophysics is a very broad subject,astrophysicists apply concepts and methods from many disciplines of physics,including classical mechanics,electromagnetism,statistical mechanics,thermodynamics,quantum mechanics,relativity,nuclear and particle physics,and atomic and molecular physics.
Anomalous X-ray pulsars (AXPs) are an observational manifestation of magnetars—young,isolated,highly magnetized neutron stars. These energetic X-ray pulsars are characterized by slow rotation periods of ~2–12 seconds and large magnetic fields of ~1013–1015 gauss (1 to 100 gigateslas). As of 2017,there were 12 confirmed and 2 candidate AXPs known. The identification of AXPs with magnetars was motivated by their similarity to soft gamma repeaters.
The Bruno Rossi Prize is awarded annually by the High Energy Astrophysics division of the American Astronomical Society "for a significant contribution to High Energy Astrophysics,with particular emphasis on recent,original work". Named after astrophysicist Bruno Rossi,the prize is awarded with a certificate and a gift of USD $500,and was first awarded in 1985 to William R. Forman and Christine Jones Forman "for pioneering work in the study of X-ray emission from early type galaxies". It has been awarded 32 times. In 2010,the prize was awarded to William B. Atwood,Peter Michelson and the Fermi Gamma-ray Space Telescope team "for enabling,through the development of the Large Area Telescope,new insights into neutron stars,supernova remnants,cosmic rays,binary systems,active galactic nuclei,and gamma-ray bursts". In 2013,the prize was awarded to Roger W. Romani of Leland Stanford Junior University and Alice Harding of Goddard Space Flight Center for their work in developing the theoretical framework underpinning the many exciting pulsar results from Fermi Gamma-ray Space Telescope.
The Tolman–Oppenheimer–Volkoff limit is an upper bound to the mass of cold,non-rotating neutron stars,analogous to the Chandrasekhar limit for white dwarf stars. If the mass of a neutron star reaches the limit it will collapse to a denser form,most likely a black hole.
A radio-quiet neutron star is a neutron star that does not seem to emit radio emissions,but is still visible to Earth through electromagnetic radiation at other parts of the spectrum,particularly X-rays and gamma rays.
Knowledge of the location of Earth has been shaped by 400 years of telescopic observations,and has expanded radically since the start of the 20th century. Initially,Earth was believed to be the center of the Universe,which consisted only of those planets visible with the naked eye and an outlying sphere of fixed stars. After the acceptance of the heliocentric model in the 17th century,observations by William Herschel and others showed that the Sun lay within a vast,disc-shaped galaxy of stars. By the 20th century,observations of spiral nebulae revealed that the Milky Way galaxy was one of billions in an expanding universe,grouped into clusters and superclusters. By the end of the 20th century,the overall structure of the visible universe was becoming clearer,with superclusters forming into a vast web of filaments and voids. Superclusters,filaments and voids are the largest coherent structures in the Universe that we can observe. At still larger scales the Universe becomes homogeneous,meaning that all its parts have on average the same density,composition and structure.
Michael J. Kurtz is an astrophysicist at Harvard University,He has held the title of Astronomer at the Center for Astrophysics | Harvard &Smithsonian since 1983,and the additional post of Computer Scientist at the Smithsonian Astrophysical Observatory since 1984. He is especially known both for his research into the distribution of galaxies,and for his creation of the Astrophysics Data System.
HakkıBoran Ögelman was a Turkish physicist and astrophysicist. He was an expert on gamma ray astronomy,the physics of neutron stars,and solar energy and worked on several key topics in modern astrophysics. He made many contributions to high energy astrophysics. In his early professional career he engaged in the SAS-II Small Gamma Ray Astronomy Satellite experiment development,data analysis,and first detection and imaging of our universe in gamma rays with his NASA colleagues,as well as in other fields of physics. His main interests in the field of astrophysics were the study of gamma ray astronomy and compact objects such as neutron stars and pulsars. Ögelman worked at NASA Goddard Space Flight Center,Middle East Technical University (METU) in Ankara,Turkey,Çukurova University in Adana,Turkey,Max Planck Institute (MPI) at Garching,Germany and the University of Wisconsin.
Dr. Robert J. Nemiroff is a Professor of Physics at Michigan Technological University. He received his Ph.D. from the University of Pennsylvania in Astronomy and Astrophysics in 1987 and his B.S. from Lehigh University in Engineering Physics in 1982. He is an active researcher with interests that include gamma-ray bursts,gravitational lensing,and cosmology,and is the cofounder and coeditor of Astronomy Picture of the Day (APOD),the home page of which receives over a million hits a day,approximately 20% of nasa.gov traffic. He is married and has one daughter.
Adam Burrows is a noted professor of astrophysical sciences at Princeton University.
Fiona A. Harrison is the Kent and Joyce Kresa Leadership Chair of the Division of Physics,Mathematics and Astronomy at Caltech,Harold A. Rosen Professor of Physics at Caltech and the Principal Investigator for NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) mission. She won the Hans A. Bethe Prize in 2020 for her work on NuSTAR.
Chryssa Kouveliotou is a Greek astrophysicist. She is a professor at George Washington University and a retired senior technologist in high-energy astrophysics at NASA's Marshall Space Flight Center in Huntsville,Alabama.
Alice Kust Harding is an American astrophysicist at the NASA Goddard Space Flight Center,Greenbelt,Maryland.
Imaging X-ray Polarimetry Explorer,commonly known as IXPE or SMEX-14,is a space observatory with three identical telescopes designed to measure the polarization of cosmic X-rays of black holes,neutron stars,and pulsars. The observatory,which was launched on 9 December 2021,is an international collaboration between NASA and the Italian Space Agency (ASI). It is part of NASA's Explorers program,which designs low-cost spacecraft to study heliophysics and astrophysics.
James Wellington Truran Jr. was an American physicist,known for his research in nuclear astrophysics.
Christopher Thompson is a Canadian astronomer and astrophysicist. He is a professor of astronomy at the University of Toronto Canadian Institute for Theoretical Astrophysics (CITA).
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