Core Carols 4: "Hark, the Herald Angels Sing"

The slides and videos in this series come from recent exploration of "The Upper Room Rockers" concerning classic Christmas carols. We touch on the often surprising origins of these songs, their use of what's in the Bible, and their  guesses beyond what's in the Bible.  Today's entry is: "Hark, the Herald Angels Sing".

Question: What is a "herald"?

Hints:

In 1965, "A Charlie Brown Christmas" changed all the words to "loo".

Let the same mind be in you that was in Christ Jesus,
who, though he was in the form of God,
    did not regard equality with God
    as something to be exploited,
but emptied himself,
    taking the form of a slave,
    being born in human likeness.
- Paul, in his letter to the Philippians

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What do you call these lines coming out of the sun?
Here is another name for them.

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