You need a structural engineer. Yes your floor joists could span the distance but this beam is also supporting the roof. If you have any kind of snow loads at all I suspect this beam is already undersized.

Do nothing until you have a structural engineer look at the situation and give you recommendations. Load tables are meaningless if you don't know the wood framing species and grade.

Often those beams are not just supporting the floor above, they are holding the ends of the cabin in place.

There's a reason it's there. If it wasn't needed, that addition wouldn't have it.

Yeah, that's holding the ends of your house together, I'd bet.

Call a structural engineer.

Looks like the beam is 2x8 (x2) for 20' span ... I doubt it can hold any weight. 4x14 glulams may be. Call a structural engineer. It can probably be relocated the the attic.

Brian: It may not be holding any weight. It may be in tension--holding things together, like the end walls of the house.