One interpretation of the 7 Heavens in the Quran is ALSO the universe/multiple galaxies in the universe
7 Heavens has multiple interpretations. Whenever reference is made to the 7 Heavens being in layers or one on top of another, then 7 Heavens is understood to be the atmosphere.
In the verses below however ,7 Heavens is best understood to be the universe
Quran 17-44
The seven heavens and the earth and all that is therein, glorify Him and there is not a thing but glorifies His Praise. But you understand not their glorification. Truly, He is Ever Forbearing, Oft-Forgiving.
Quran 78 (12-13)
7 Strong implies the 7 Heavens and in this context it is the universe.
And We have built above you seven strong
And We have made (therein) a shining lamp(Sun)
Allah SWT knows best