Answer to Question #90282 in Astronomy | Astrophysics for Shivam Nishad

Question

What is interstellar extinction ? How does it help in determining the composition of ISM ?

Answer 1

Interstellar extinction is a phenomenon first noted in 1847 by Struve and documented in 1930 by Trumpler. The phenomenon can be described as absorption and scattering of electromagnetic radiation (emitted by some astronomical object) by cosmic dust and gas between an observer and an astronomical object. A simple example from everyday life can be the extinction of sunlight due to clouds or dust which we observe from the ground. For instance, galaxies in the plane of Milky Way some thousand parcecs away from the Earth have interstellar extinction of 1.8m per 1 kiloparsec.

As we know from physics, the way the radiation becomes weaker depends on the content of a medium in which this radiation propagates. By getting extinction curves we can determine the composition of the interstellar medium (ISM).