Answer: What the appositive "a Swedish astronomer" renames is Samantha Bernard.
Explanation: An appositive is a noun or a noun phrase that is included in a sentence in order to rename a noun that is found next to it. There are two types of appositives: essential appositives, which are not separated from the rest of the sentence, and nonessential appositives, which are found between commas and separated from the other elements in the sentence. In the case of this sentence, "a Swedish astronomer" is a nonessential appositive and it is renaming the noun that it is beside it: Samantha Bernard.
