Mid-infrared spectroscopic data on SN 1987A are reviewed. This spectral region contains the fine structure lines of a number of ions, incuding the iron group elements, together with recombination lines of hydrogen and helium. From about 9 months all these lines and the continuum have been effectively optically thin, and the [CoII] line strength and development yields an estimate of the parental 56Ni mass of 0.071 M⊙, very similar to the light curve estimates. At one year after the explosion the velocities appropriate to the hydrogenic and ionic regions are ∼ 2000 km s−1 and ∼ 1500 km s−1, respectively.

Apart from an excess between 8–9 μm which appears to be due to molecular SiO, there is no evidence of departure of the continuum from free-free emission, and no sign of any emission from dust. From the free-free continuum an ionization fraction of a few percent is derived for the hydrogen/helium envelope; this provides relative transparency in the mid infrared while the bound electrons provide the X and γ-ray opacity which is still considerable at 15 months.

The appearance of neutral ions at 15 months indicates that the ejecta temperatures are cooling, and that dust formation may be imminent.

The extremely rare occurrence of a relatively nearby supernova, SN 1987A, provides astronomers with a unique opportunity to conduct the most detailed multi-wavelength analysis of this event and its effect on the ambient medium. Looking inside the supernova, astronomers are getting their first ‘unbiased’ view of the composition of the expanding ejecta. The infrared (IR) region of the spectrum can carry the signature of products ranging from heavy elements, synthesised during the early phases of the expansion, to molecules and dust formed after the ejecta underwent significant cooling. Probing the ambient medium, IR observers can gain information on the presence and distribution of dust in close proximity (∼1 pc) to the supernova (SN), and on the interaction of the SN blast wave with the surrounding dusty medium. At larger distances from the SN, they can set constraints on dust properties in the scattering dust layers detected at distances of ∼120 and ∼330 pc from the supernova.

SN 1987A is sufficiently close to allow a unique examination of the morphology of a supernova, using speckle interferometry. Several groups [Center for Astrophysics (CfA); Imperial College (IC); Mount Stromlo and Siding Spring Observatories/Anglo-Australian Observatory (M/A)] have reported optical speckle observations. At Hα, both CfA and M/A have determined the angular extent of the emission, and reasonable agreement is obtained. The speckle-derived values are consistent with those obtained from line profiles. IC has also succeeded in resolving the supernova at Hα. At wavelengths other than Hα, at early epochs, angular diameters obtained by CfA are larger than those derived from photometric and spectroscopic measurements, possibly due to scattering effects. At later epochs, the diameters exhibit little variation between the wavelengths examined. CfA reports significant asymmetry in the late epoch data.

Several attempts have been made to re-observe (at optical wavelengths) the companion object, but none have succeeded. The nature of this phenomenon is still controversial, but the evidence indicates that the companion was real, with emission from dust apparently being the least problematic explanation. Support for this may lie in IR speckle observations (Haute Provence/Lyon) which, on about day 115, indicated the presence of one or more resolved components at an angular displacement comparable to that of the optical companion.

Results of the observations of SN 1987A from Ginga are presented. The first detection of X-rays from the SN 1987A was July, 1987. The energy spectrum is quite unnusual for any of the known classes of X-ray sources, and apparently consists of two seperate components; a soft and a hard component. The soft component is significantly time-variable, and also showed a flarelike increase in January, 1988. Whereas, the intensity of the hard component has remained fairly stationary for more than 300 days. The origins of the two components are also discussed.

SN 1987A has been observed with a combined high energy γ-ray (50-500 MeV) and hard X-ray (15-150 keV) payload during a balloon flight on 5 April 1988 from Alice Springs, Australia. The γ-ray observations, along with our earlier ones on 19 April 1987 are the only such observations of the supernova to date. The γ-ray detector characteristics are described. The preliminary results of the recent flight and their implications in terms of the known supernova parameters are discussed.

We summarise recent developments in modelling SN 1987A including the progenitor’s evolution, explosive nucleosynthesis, optical, X- and γ-ray light curves, and dust formation. The distribution of heavy elements in the ejecta is inferred from the light curves. The pre-peak optical light curve as well as early emergence of X- and γ-ray indicate the mixing of 56Ni into the hydrogen-rich envelope. The plateau-like peak of the optical light curve is well reproduced if hydrogen is mixed into the deep core. The flat X-ray light curve observed by Ginga would be due to the clumpy structure of the core. The progenitor’s blue-red-blue evolution and nitrogen abundance suggest that the progenitor’s hydrogen-rich envelope had mass Menv = 7 − 11 M⊙ and was almost completely mixed.

This conference has shown that the accumulated wealth of data on SN 1987A has enabled us to learn an unprecedented amount of physical information about a single supernova event and supernovae in general, as well as to confirm much of the heretofore established theory. While some difficult problems remain, I discuss some particularly simple and useful theoretical notions concerning the bolometric and γ-ray light curves which can be gleaned from our current body of knowledge, drawing primarily upon results of analytic work performed by W.D. Arnett and myself. Also, the work of Lamb, Melia and Loredo (1987) on neutrinos from the supernova is discussed briefly.

SN 1987A has illuminated a great diversity of astrophysical processes – from neutrino emission during core collapse to the structure of the interstellar medium on a scale of hundreds of parsecs. Here I cover the evolution of SN 1987A from the outside in; the topics are interstellar light echoes, circumstellar light echoes, circumstellar shock waves, late emission and structure of the ejecta, and the effects of a central neutron star.

In the first part the UV and optical observations of the circumstellar gas of SN 1987A are reviewed, and the physical properties of the gas discussed. In the second part models of the emission are treated, as well as their use as a diagnostic of the radiation from the supernova during the first, unobserved hours after the explosion.

The exceptional brightness of SN 1987A has provided a unique opportunity to probe intervening gas clouds in the disk and halo of our Galaxy and in the Large Magellanic Cloud, as well as intergalactic matter between the two. At the AAO we have exploited this opportunity in two ways: in searches for very weak interstellar features requiring exceptionally high signal-to-noise ratio spectra, and in recording known interstellar lines with unprecedentedly high spectral resolution. We are also monitoring photographically the evolution of the light-echoes to map the three-dimensional distribution of interstellar matter near the supernova. Surprisingly high column densities of million-degree gas have been found in the LMC through the first detection of [Fe X] in absorption. The hot gas may fill the interior of a ‘superbubble’, created by the combined effects of previous supernovae in this active region of star-formation; this cavity may be related to the shells of interstellar matter giving rise to the light-echoes. The ultra-high resolution observations, which required the rapid construction of a dedicated new spectrograph, were successful in resolving the hyperfine structure of the sodium D lines in several interstellar clouds. This implies that the clouds are at temperatures of at most 170 K and have internal turbulent velocities of no more than 0.3 km s−1, even though some are moving with high velocities relative to the Sun.

The influence of the progenitor’s stellar wind on the supernova event, and subsequent development of a remnant are discussed. Various morphological differences between SN remnants and the implications for previous wind activity are described. A detailed look at the effects in the ring nebula NGC 6888 is presented.

I review the observed properties of supernovae (SNe), concentrating on recent results obtained from high-quality optical spectra. Although most SNe Ia have similar characteristics at comparable phases, there are some notable variations, particularly in the velocities of the ejecta. Moreover, there is very preliminary evidence for significant differences between the spectra of SNe Ia in H II regions and in elliptical galaxies. SNe II exhibit a wide range of spectral properties, as expected if they are produced by massive stars. At late times strong lines of [O I] and [Ca II] appear in most SNe II, including SN 1987A. In some objects, however, these are absent; the spectrum of SN 1987F, for instance, closely resembled that of a Seyfert 1 nucleus, with prominent H I and Fe II emission lines. Type Ib SNe, which lack the 6150Â absorption band typical of SNe la near maximum brightness, develop strong emission lines of [O I] and [Ca II] many months past maximum, but hydrogen is absent. Hα emission with a P-Cygni profile has, on the other hand, been detected in the early-time spectrum of SN 1987K, an object which later became spectroscopically indistinguishable from an old SN Ib. There is evidence for very weak Hα in the early spectra of several additional SNe Ib. Moreover, 7 – 8 months past maximum the [O I]/Hα and [Ca II]/Hα intensity ratios in SN 1987A were higher than in a few other well-observed SNe II at corresponding times. Hence, Type II and Type Ib SNe may form a continuous sequence in which the mass of the hydrogen envelope is the main variable.

Expectations and results of searches at radio and optical wavelengths for a pulsar in SN 1987A are described.