Astronomical instrumentation

Abstract:

Infrared spectroscopy has allowed the identification of a number of different components of interstellar dust. Refractory species such as silicates and silicon carbide are commonly seen in circumstellar dust, whilst the former also dominate the infrared absorption by interstellar dust. In addition, spectral features from a number of more volatile species condensed on grains have been measured in cold, sheltered regions such as molecular clouds and dense circumstellar outflows from cool evolved stars. In diffuse regions, and particularly in ionization fronts and photodissociation regions close to hot stars, the infrared emission spectrum is dominated by a family of narrow emission features between 3 and 13μm produced by small carbon-rich grains. Recent observations have shown that there are a number of weak bands in addition to the well-known strong features. -from Author

Abstract:

The mid-infrared emission (at wavelengths near 10 μm) from SN1987A, which had been fading steadily since reaching a peak about 120 days after outburst, began to increase again on about day 4501. This increase has continued up to at least day 578, and is probably due to heating of dust grains by light emitted at the optical maximum. Here we present additional observations and discuss the mass, location and nature of the emitting dust. The dust grains cannot have formed in the ejecta of the supernova, nor do they appear to be symmetrically distributed about it; rather, they are located at a distance of about 1 light year from, and mostly behind, the supernova. © 1989 Nature Publishing Group.