  Ever since the first discovery of Poynting and Robertson, the radiation
source has been treated as merely a point. Even in a very few studies where the
size of the source has been taken into account, the treatment of the problem
remained largely non-relativistic. In the present work, we address the issue of
the finite size effects on the Poynting-Robertson effect in a fully
relativistic manner for the first time. As a result, the emergence and the
characteristic of the critical point/suspension orbit can be studied in a
systematic and detailed manner.
