On April 20, 2016, Prof. Richard McCray visited NAOC and gave a lecture about observations of  Supernova (SN) 1987A and its remnant over the last 29 years. Prof. McCray is currently based at the University of California, Berkeley and has visited China more than a dozen times since the early 1980s. In the intervening time, he has enjoyed a long and productive relationship with the Chinese astronomical community and in 1996, he was also appointed as Concurrent Professor of Astrophysics at Nanjing University.  

Prof. McCray started his talk by saying that the remnant of SN 1987A is always changing and evolving, and stated that SN 1987A was the first instance of an SN to be observed across the entire electromagnetic spectrum. He later displayed light curves of the SN since its original explosion in various wavelengths including near-infrared, visible and X-ray. Using these light curves, he showed how decays of elements produced in the original explosion contributed to early heating of the resulting ejecta, and later how collision of the ejecta with the surrounding medium also generated radiation. He also explained that SN 1987A has provided astronomers with a unique opportunity to verify models of the evolution of an SN and its associated remnant.  

Prof. McCray continued by demonstrating how the observed structure of the ejecta can be accurately modeled by hydrodynamical simulations. He described how the three-dimensional (3D) structure of the expanding ejecta can be tracked by using Doppler tomography and displayed images and spectra of the SN remnant that were acquired with the Space Telescope Imaging Spectrometer (STIS) instrument on the Hubble Space Telescope (HST). From these observations, he and his group constructed a 3D computer model of the ejecta which he showcased for the audience. In the end, he said that recent observations of the SN 1987A remnant by ALMA will provide even better data that can be used to track the expanding ejecta and stated that these new results will be published in the near future.