Props Valroa

Billions of years ago there was a world around a blue star. Named Melancholia. The planet had no life, but it's oceans were amazing and sparkling blue. The sky was a deep blue color, and the sun was a large, bluer color in the sky. 

It's star was larger than ours, and massive and blue. It would die before life even evolves on Melancholia. However there was a massive gas giant world that came close to Melancholia's orbit, launching the planet out into space. The oceans froze and it was hurled out into the darkness.

Fast forward to modern times, the planet entered our solar system from behind the sun and oceans began to thaw out and the beauty of the world would return but it would last for a very short time before Melancholia and Earth collided, Melancholia assuming it's orbit around our sun in place of earth. A new chapter of life would begin on this world. Our moon taking it's place in Melancholia's skies.