Noun and の adjective
こうせい
ブラックホールが、恒星をばらばらに引き裂くことがあるらしい。
The black hole appears to be tearing that star to pieces.
A constant star is the kind that stays in one place. It's just a regular star, like the north star or our sun, not a comet or an asteroid.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.