I think the ending was an effect of time dilation that close to a star, yeah, plus it’s Capa’s perception of what’s happening. They frequently have people die from sun exposure in the film, so it’s not very likely that they’d suddenly forget that being in the sun itself would be rather bad.
It’s a shame they didn’t explain that they didn’t mean the sun was just dying; the q-bomb thing is pretty implausible too, but it’s not the utter stupidity most people seem to assume it is.
And apparently the few seconds in space but surviving thing isn’t so unlikely - on the other thread someone linked to an article that’s not there now, saying that no, you wouldn’t instantly die. Besides, one of them did die and the other was injured, so it’s not like ‘nothing happened to them.’