Paul uses a question for emphasis. AT: "But, I say the Jews certainly have heard the message about Christ." (See: [[rc://en/ta/man/translate/figs-rquestion]], [[rc://en/ta/man/translate/figs-quotations]])
Both of these statements mean basically the same thing and are used for emphasis. The word "their" refers to the sun, moon, and stars. Here they are described as human messengers that tell people about God. This refers to how their existence testifies to God's power and glory. It can be made explicit that Paul is quoting Scripture here. AT: "As it is written in the Scriptures, 'The sun, moon, and the stars are proof of God's power and glory, and everyone in the world sees them and knows the truth about God'" (See: [[rc://en/ta/man/translate/figs-parallelism]] and [[rc://en/ta/man/translate/figs-personification]] and [[rc://en/ta/man/translate/figs-explicit]])