Answer: Hello mate!
The first blank is Astronomy, which is the science that studies the space, planets, and in general things outside the earth itself.
The second blank is Meteorology, which is the science that studies the wheater in the planet.
Then the phrase would be:
Both of these studies have to do with the sky. However, astronomy focuses on space and structures within it, like stars and meteoroids, and meteorology focuses on weather elements, like wind currents and cold fronts.