Here we review how binary interactions affect the final pre-supernova structure of massive stars and the resulting supernova explosions. (1) Binary-induced mass loss and mass accretion determine the final envelope structure, the mass, radius and chemical composition, which are mainly responsible for the supernova appearance and supernova (sub-)type. (2) Mass loss can also drastically change the core evolution and hence the final fate of a star; specifically, around 10 M⊙, it determines whether a star explodes in a supernova or forms a white dwarf, while for larger masses it can dramatically increase the minimum main-sequence mass above which a star is expected to collapse to a black hole. (3) Mass loss before the supernova directly affects the circumstellar medium (CSM) which can affect the supernova spectrum (e.g. account for the IIn phenomenon), produce powerful radio emission and, in extreme cases, lead to a strong interaction with the supernova ejecta and thus strongly modify the lightcurve shape; it may even be responsible for some of the superluminous supernovae that have recently been discovered.

As has been shown previously, the triple-ring nebula around SN 1987A can be understood as a direct consequence of the merger of two stars, some 20,000 yr before the explosion. Here we present new SPH simulations that also include the pre-merger mass loss and show that this may be able to explain other structures observed around SN 1987A, such as Napoleon's hat and various light echoes.

The one-in-a-life-time event Supernova SN 1987A, the brightest supernova seen since Kepler's in 1604, has given us a unique opportunity to study the mechanics of a supernova explosion and now to witness the birth of a supernova remnant. A violent encounter is underway between the fastest-moving debris and the circumstellar ring: shocks excite “hotspots”. ATCA/ANTF, Gemini, VLT, HST, Spitzer, Chandra, and recently ALMA observations have been so far organized to help understanding the several emission mechanisms at work. In the mid-infrared SN 1987A has transformed from a SN with the bulk of its radiation from the ejecta to a SNR whose emission is dominated by the interaction of the blast wave with the surrounding interstellar medium, a process in which kinetic energy is converted into radiative energy. Currently this remnant emission is dominated by material in or near the inner equatorial ring (ER). We give here a brief history of our mid-infrared observations, and present our last data obtained with the SPITZER infrared satellite and the ESO VLT and Gemini telescopes: we show how together with Chandra observations, they contribute to the understanding of this fascinating object. We argue also that our imaging observations suggest that warm dust is still present in the ejecta, and we dispute the presence of huge amount of very cold dust in it, as it has been claimed on the basis of data obtained with the HERSCHELl satellite.