The Remnant of Supernova 1987A

Although it has faded by a factor of ∼10⁷, SN 1987A is still bright enough to be observed in almost every band of the electromagnetic spectrum. Today, the bolometric luminosity of the debris is dominated by a far-infrared (∼200μm) continuum from ∼0.5 M_⊙ of dust grains in the interior debris. The dust is heated by UV, optical, and near-infrared (NIR) emission resulting from radioactive energy deposition by ⁴⁴Ti. The optical light of the supernova debris is now dominated by illumination of the debris by X-rays resulting from the impact of the outer supernova envelope with an equatorial ring (ER) of gas that was expelled some 20,000 years before the supernova explosion. X-ray and optical observations trace a complex system of shocks resulting from this impact, whereas radio observations trace synchrotron radiation from relativistic electrons accelerated by these shocks. The luminosity of the remnant is dominated by an NIR (∼20μm) continuum from dust grains in the ER heated by collisions with ions in the X-ray emitting gas. With the Atacama Large Millimeter Array (ALMA), we can observe the interior debris at millimeter/submillimeter wavelengths, which are not absorbed by the interior dust. The ALMA observations reveal bright emission lines from rotational transitions of CO and SiO lines that provide a new window into the interior structure of the supernova debris. Optical, NIR, and ALMA observations all indicate strongly asymmetric ejecta. Intensive searches have failed to yield any evidence for the compact object expected to reside at the center of the remnant. The current upper limit to the luminosity of such an object is a few tens of solar luminosities.