Will an off-topic Masters hurt my chances of a PhD place? 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?
Don't ask us.

Contact your favourite three prospective universities for your cosmology PhD. Better still, contact your favourite three supervisors for your cosmology PhD. Ask them:


What Master's dissertation topic will prepare me best for my intended cosmology studies?
What Master's dissertation topic will make me most likely to be successful when applying to study a cosmology PhD?


(The first question is much more interesting than the second).

You will find enthusiasm for engaging with your question and your situation, because you are expressing specific interest in their field and because you are not asking them to decide anything about your application – since you have not applied. Quite a lot of people in senior levels in cosmology are interested in cosmology and are glad to find interest in cosmology in other people.