Supernova 1987A: 20 years later

It is 20 years since supernova 1987A, the brightest supernova in more than 400 years, was discovered. Several international symposiums were held in 2007, NASA released a special and beautiful SN1987A color photograph taken by the Hubble space telescope, and commemorative stamps were issued by the USA, all for celebrating SN1987A. We present an overview of its discovery, the spectra and character of its progenitor, the rich data accumulated over long term observations by the Hubble telescope, especially the three-ring structure, and the results of the Chandra X-ray observatory. Although SN1987A has been observed continuously, its central compact object has still not been discovered and certain mysteries remain unexplained. Finally, we look into the future.