I have just completed the third year of an integrated master's degree (a three-year undergraduate degree plus an additional year of study at a master's degree level, with the final degree being an MPhys) in Astrophysics at a UK university. This summer I have to decide the topic of my final year dissertation, which counts for 50% of my final year.
I am almost certain I would like to continue in research and hence I am also starting to look for PhD places. I am very interested in cosmology, but with no idea of a specific area I want to go into and so I had thought of doing something in the field for my Master's dissertation, to get an idea of what it would be like to perform cosmology research.
However, the university I am at does not have a research group in this area and no facilities or expertise either. I have approached a potential supervisor (the lecturer who taught my one cosmology module, who is a plasma physicist), but he has told me that it is entirely up to me to decide on a topic/ question, which I am wary of doing due to my complete inexperience and lack of knowledge.
So, my question is this: if I decide to do my Master's dissertation on a different topic (eg solar physics), will I be at a disadvantage when applying for cosmology PhDs?