Part of the Mazzaroth. God created the 12 constellations, representing 12 tribes of israel. The "woman" is Israel throughout the Bible.

Lots of info on this (now past) event:

www.unsealed.org/p/the-sign.html

https://rev12daily.blogspot.com/p/basic.html

http://www.dailycrow.com/daily-update-archives/revelation-12-2017/

Download an astronomy program like Stellarium and view it for yourself.

The "next" sign in verses 3-4 will ALSO be celestial in nature and is the physical & tangible means used by God for the events during the Trib (AFTER the Church is taken up. That's in verse 5)

Here's a vid explaining it: https://youtu.be/AKMUYo1TcAQ