Astrophysics and Space Science

, Volume 140, Issue 1, pp 191–203 | Cite as

Interstellar extinction by cometary organic grain clumps

  • F. Hoyle
  • N. C. Wickramasinghe


The observed features of the interstellar extinction curve in both the Galaxy and in the external galaxies LMC and SMC are explained on the basis of a model involving clumps of hollow or porous organic particles with an overall volume filling factor of 0.1. The hollow organic particles have a ready explanation in terms of the bacterial grain model. The visual and near infrared observations of extinction are fitted by a size distribution of such aggregates similar to the distribution law discovered for the larger grains in Halley's comet, but with a cutoff at low radii taken at 0.5 μm for the Galaxy and 0.3 and 0.4 μ, respectively, for SMC and LMC. Fine tuning of the theoretical extinction curve to fit observational data in the ultraviolet involves variable contributions from small condensed polymeric units of typical radius 0.012 μm and graphite particles of radii 0.02 μ. These particle species may be regarded as being derived from the primary distribution of clumps. The implication is that cometary sources could provide a major component of the grains in interstellar space.


Graphite Particle Volume Filling Organic Particle Variable Contribution Particle Species 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© D. Reidel Publishing Company 1988

Authors and Affiliations

  • F. Hoyle
    • 1
  • N. C. Wickramasinghe
    • 1
  1. 1.Dept. of Applied Mathematics and AstronomyUniversity CollegeCardiffWales, U.K.

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