The noun clause is how the Aztecs made their astronomical calculations.
Just invert the whole sentence - The subject of my next paper is <em>how the Aztecs made their astronomical calculations.
</em><em />The whole clause is used as the direct object.
Loved Ik to Juliet because they were both part for the longest of the family battles
(1) Adverb Clause of Reason
(1) Adverb Clause of Reason