That is a fact. Facts can be proven. A theory is more involved. Think Newton's theory of gravity. It sure seemed true, it tested true on earth. Then Einstein comes along with a better explanation. We can't know that someone else won't come up with an even better theory so we can't prove Einstein correct. We can only fail to disprove it.
So it hasn't yet been proven that the earth revolves around the sun?
That is a fact. Facts can be proven.
I have to disagree with both of these sentences.
1) A fact is a confirmed observation. No one has observed heliocentrism as a singular (or even a complex) fact. What we observe is that a light in the sky (a planet) traces such and such a path of polar co-ordinates across the night sky. Granted that this condition has been considerably augmented in recent decades by observations from space craft, but these observations still comprise a large collection of individual facts/observations. It is because these facts are uniquely consistent, among available coherent views, with the heliocentric view that we conclude that heliocentrism is true, but it is still an inference rather than a fact itself.
2) Facts are not proven. If a fact is a "confirmed observation" then we must always be open to the possibility that disconfirming observations may come to light in the future. As a specific example, it was "a fact" (a confirmed observation) until 1956 that there where 48 human chromosomes. After that time improvements in staining techniques corrected earlier observations, and the number of human chromosomes "changed" to the currently accepted number of 46. See History of human cytogenetics.