even so; however; even though~
Connects two sentences to show that the second fact contradicts expectations from the first, like 'however' or 'even so'.
ところが is used to introduce a result or fact that goes against what the first sentence made you expect. It is similar to 'however' in English, but it is more strongly contrastive—it often marks a surprising twist. For example, you might say 'I studied hard for the exam. However, I failed.' The second part is unexpected given the first.
This is a written and spoken conjunction, but in conversation it can sound a bit formal. Often people use でも or けど for a lighter contrast. ところが is also a set phrase, not a particle, so it always starts a new sentence or clause.
Be careful: ところが also exists as a different grammar point meaning 'far from' or 'anything but', used after dictionary forms (e.g., 言うところが). That is a separate pattern, and the meaning is opposite. In this entry we only cover the 'however' meaning.