((Luke must have done extensive research and interviews with all the people who had firsthand knowledge of all the accounts that he writes down. He goes into such detail.))

11 And an angel of the Lord appeared to him, standing to the right of the altar of incense.
12 Zacharias was troubled when he saw the angel, and fear gripped him. ...
... 19 The angel answered and said to him, “I am Gabriel, who stands in the presence of God, and I have been sent to speak to you and to bring you this good news. ...
... 26 ¶ Now in the sixth month, (Elizabeth's 6th month of pregnancy with John the Baptist)), the angel Gabriel was sent from God to a city in Galilee called Nazareth,
27 to a virgin engaged to a man whose name was Joseph, of the descendants of David; and the virgin’s name was Mary. ...
... 39 ¶ Now at this time Mary arose and went in a hurry to the hill country, to a city of Judah,
40 and entered the house of Zacharias and greeted Elizabeth.

Matt. 1;20
20 But when he,(Joseph), had considered this, behold, an angel of the Lord ,(probably Gabriel but we aren't told for sure), appeared to him in a dream, saying, “Joseph, son of David, do not be afraid to take Mary as your wife; for the Child who has been conceived in her is of the Holy Spirit.

((FIRST; is this miraculous pregnancy foretold to Zacharias; that his wife Elizabeth would get pregnant and then have John the Baptist. What made This miraculous is Zacharias and Elizabeth were both well past the child bearing age. (Verse 6 tells us they were both "righteous in the sight of the Lord. Walking blamelessly in all the commandments and requirements of the Lord"). And now they were going to have a son who fulfilled prophecies written 100's of years earlier.
Is. 40:3-5(700bc),
Mal. 3:1(430bc),
Mal. 4:5(430bc).

SECOND; Gabriel appears to Mary some 6 months later and tells her she is going to be pregnant with Jesus through a miraculous conception by the Holy Spirit, (prophecies in Isaiah 7:14. Roughly written 709bc). And Mary immediately goes to Elizabeth and Zacharias' house. She is already pregnant with Jesus and John the Baptist in his mothers womb is already full of the Holy Spirit and leaps in the womb when Mary walks in. Elizabeth is 6 months pregnant and Mary stays with her for 3 months. At which time she returns home.
THIRD; According to Matt. 1:20 Joseph is visited by an Angel of the Lord who I believe to be Gabriel although we aren't told for sure. But Joseph immediately takes Mary as His wife and marries her. {Don't you know there were a lot of small town gossiping going on that town}.
Luke by far has the most detailed account of the events leading up to the birth of Jesus but we need to read all that the Bible contains surrounding our saviors birth. As we head into the Christmas season always remember what it is about. Do some reading and cross referencing and take in the whole story. Gabriel must have been so excited. Just think about all the hosts of angels singing in the night sky before the shepherds. All heaven celebrated this event. And Gabriel got to be at the fore front of it all.)) ((Father thank you for preserving Your word, Your story, that each of us can read it and worship You everyday with our hearts and spirit. Lord thank You for sending Your Son, Jesus to be our savior. You love each one of us so much. We can never repay the debt we owe. Even now, knowing that I have been covered in the blood of Jesus, I still am a sinner with no good works. You are the one true and righteous God. Thank You for Your great love. Amen))
((Please remember to pray for our country and its leaders. Pray for Israel and pray for each other. Thank you.)) ((be all you can be for God today. PRAY, READ, LISTEN and DO.))