I am currently pursuing master's in Physics. In my university, there aren't many professors in my field of interest i.e. Astrophysics, the professors whose work I was interested in, declined me the project cause I asked them late. So, I joined another professor, telling him that I am interested in Astrophysics and want to do project in Fluid Dynamics. He accepted and offered me one, that have application of fluid dynamics in biophysics. I thought this since fluid dynamics is used in Astrophysics studies as well, and in my topic of interest i.e. star formation and galaxy dynamics.
Now, I am pretty sure for now, I want to go into Astrophysics. My question is for higher studies what ways could doing a master's thesis in a topic other than interest, hinder my chances of getting PhD admission?
If cons, what could I do to improve my chances?
And if pros, please list them.
I started my project a month ago.