I saw this question titled "Is the sun shrinking currently?" on astronomy SE, then I was wondering could I use the word "does" instead of "is"? Then I give Textranch a try, but they only double lined the latter phrase and didn't give an explanation. So why is the phrase "Does the sun shrinking currently?" incorrect?
To answer your question why "does" is incorrect is because it is the third person present tense of "do" and hardly makes sense in this sentence, because you have already referred to the present time frame using the word "currently". "is" is denoting the continuity of the process (a continuation of the process in the present time), whereas "does" refers to an instant of the time.
One can rephrase the sentence as "Does the sun shrink?". Now that sounds more like a brick on the face, as if the sun always shrinks or it does not, no alternative answer.