before the iso mission was launched the commonly accepted theory of dust formation in post-agb objects was that carbon-rich nebulae formed carbon dust (either pah.s, amorphous carbon or graphite) and oxygen-rich nebulae formed a mixture of minerals commonly called 'silicates.. also oxygen-rich chemistry should not take place in carbon-rich nebulae. once the first sws and lws spectra from iso became available it soon became clear that this theory was too simple. the first indication was the lws spectrum of ngc 7027 (a carbon-rich nebula) were a clear detection of both an oh and an h20 line was found. also in the spectra of the oxygen-rich nebulae ngc 6302 and roberts 22 both pah features and crystalline oxygen-rich dust features were discovered. the fact that in the early part of the iso mission already three cases have been discovered which clearly refute the simple theory of dust formation in agb ejecta, is suggestive of the fact that this phenomenon might be quite common. therefore we propose, as a follow-up to the guaranteed time programme of beintema et al., a more systematic search for planetary nebulae with similar characteristics as described above. only iso can provide the wavelength coverage needed for this research.
Instrument
LWS01 , SWS01
Temporal Coverage
1997-03-24T05:01:23Z/1997-07-15T05:28:20Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the world's first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
