Comparing stars
Comparing stars

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Comparing stars

2 Observing through the interstellar medium

2.1 Introduction

In all the analysis of stellar properties discussed so far we have made an implicit assumption - that light emitted by a star is not changed between its emission and its arrival outside the Earth's atmosphere, except by the inverse square law (i.e. it is reduced by a factor of d2, where d is the distance to the star) and by the Doppler effect. However, this may not be the case.

Question 8

What will happen to the position of a star on the H-R diagram if interstellar material causes a reduction in its brightness?

Answer

If the interstellar material causes light to be absorbed then the star will appear fainter and hence be placed lower than its true position on the H-R diagram.

We will now investigate some of the properties of the interstellar material and how it affects the radiation we observe from stars.

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