Why do we study other system outside of our star system

Which revelation resulted from the observation of the spectrum of different galaxies? a. there were more galaxies whose spectrum was blueshifted b. there were no galaxies whose spectrum was redshifted c. there were more galaxies whose spectrum was redshifted d. there were no galaxies whose spectrum was blueshifted

What is the border between layers a through f and layer g called?

Which physical law states that all orbits are conic sections?