Introduction

Infrared observations have contributed substantially to our understanding of how classical novae participate in the chemical evolution of the Galaxy. We describe how infrared observations, combined with optical measurements, can provide quantitative measurements of the primary physical parameters that characterize the outburst, the abundances of elements that are present in the ejecta, and the properties of the grains that condense in the nova wind. We summarize recent evidence that novae are capable of producing large over-abundances of some metals and that they are potential sources of ‘stardust’ similar to the small grains that populate comet comae.

Nova explosions in the context of Galactic chemical evolution

Galactic classical novae take part in a cycle of Galactic chemical evolution in which grains and gas in the ejecta of evolved stars enrich the metal abundance of the Galactic ‘ecosystem’ (see Figure 8.1). Metals produced in stars during post-main-sequence (PMS) nucleosynthesis are ejected into the interstellar medium (ISM) by stellar winds and explosive events. Some of these metals remain in the gas phase, but others can condense to form grains. In the ISM, the gas and grains may become a component of the giant molecular clouds that give birth to new generations of young stars and planetary systems during the star formation process.