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SN1987A is the best-studied core-collapse supernova in the sky. We know what the progenitor was, what the circumstellar environment was, and what the explosion looked like over a broad electromagnetic bandpass and in neutrinos. For over a decade, the Chandra X-ray Observatory has been monitoring SN1987A on a regular basis, obtaining resolved images of the developing interaction with the circumstellar material, as well as high resolution grating spectroscopy of the X-ray emission. We highlight the latest results from this campaign and discuss the overall picture of the remnant's structure that emerges from these observations.
In 1996, the blast wave from Supernova 1987A began to strike the inner circumstellar ring, causing the appearance of “hot spots” on the ring. This event marks the birth of the supernova remnant, SNR1987A, defined as the epoch when the light of the event is dominated by interaction of the expanding debris of the supernova with its circumstellar matter.
Supernova and supernova remnant research are two of the most active fields of modern astronomy. SN 1987A has given us a chance to observe a supernova explosion and its aftermath in unprecedented detail, a process that continues to unfold today. Meanwhile, thanks to major advances in optical, radio, and X-ray astronomy, we have gained unprecedented views of the populations and spectrum evolution of supernovae of all kinds. These results have spurred a renaissance in theoretical studies of supernovae. Likewise, samples of well-observed supernovae are becoming large enough that we are closing fast on the goal of using supernovae to determine the cosmic distance scale.
Studies of supernovae and supernova remnants are inextricably linked and we are learning fast about the connections. We now recognize that mass loss from the supernova progenitor star can determine the structure of the circumstellar medium with which the supernova ejecta interact. An outstanding example is the ring around SN1987A. There are many supernovae in which much of the early optical, radio and X-ray emission are due to interaction of the ejecta with circumstellar matter rather than radioactivity within the supernova itself. Just in time for this colloquium, nature provided a particularly spectacular example of such an interacting supernova with SN1993J in M81, one of the brightest supernovae of this century. Moreover, the X-ray spectra of supernova remnants provide a powerful new tool to measure supernova nucleosynthesis yields.
Dramatic advances in ground-based and space astronomy, together with observations of the serendipitous supernova 1987A, have led to the study of supernovae and supernova remnants becoming one of the most active and rewarding fields in today's astrophysics. To take stock of these exciting developments and to give focus to future research, the International Astronomical Union held a colloquium in Xian, China, for the world's leading experts and this volume gathers together their articles.The articles summarise our knowledge of supernova 1987A and give the first results on supernova 1993J. They not only demonstrate the latest techniques for interpreting spectra and light curves of supernovae, but show how they can be applied to measuring the cosmic distance scale. They also cover recent advances in theories for type I and type II supernovae, and observations and interpretations of supernova remnants. Two appendices provide a unique reference of newly discovered supernovae and supernova remnants.Together these forty review articles provide an up-to-date and wide-ranging review of our understanding of supernovae and supernova remnants for graduate students and researchers.
The nebular spectra of supernovae differ from those of better-known emission nebulae in that many of the emission lines are optically thick. Here we sketch the theory for interpreting such spectra, and show how it can be used to interpret prominent emission line systems in the spectrum of SN 1987A. As examples, we describe: (1) a simple method to infer the density of OI from observations of the evolution of the doublet ratio in [O I]λλ6300; (2) new kind of hydrogen recombination hne spectrum; (3) an analysis showing that the Call infrared emission lines must come from primordial, not newly-synthesized, calcium; (4) a theory for the Fe/Co/Ni emission lines that shows that the inner envelope of SN 1987A must have a foamy texture, in which low density radioactive bubbles of Fe/Co/Ni reside in a massive substrate of hydrogen, helium, and other elements.
It's a great pleasue for me to contribute to this volume in honor of Alex Dalgarno's 60th birthday. I first met Alex when I came to Harvard as an assistant professor in 1968. From these turbulent times up to now, Alex has been a very good friend and mentor to me. From Alex I gained an interest in atomic and molecular processes that has influenced my research ever since. My writing skills improved considerably by virtue of working with him. Most important, I am grateful to Alex for setting an example of what a good professor should be, not only as a scholar and teacher, but also as a generous and loyal friend to his students and colleagues.
With Supernova 1987A (February 23, 1987), nature has provided some birthday fireworks that will be a festive reminder of Alex's many important contributions to astrophysics. The brightest supernova since SN1604 (Kepler's supernova), SN1987A is the first one that has been observed in every electromagnetic wavelength band and it is the first one that will remain observable for several years as the debris clears away to allow a detailed view of its interior. Thus, SN1987A offers an unprecedented opportunity to infer details of supernova explosion dynamics and nucleosynthesis. This task presents fascinating and challenging problems in atomic and molecular astrophysics because, as I will describe, SN1987A is remarkably cool (≥7000 K) throughout its interior and there is good evidence that CO and SiO molecules have already formed there.