In Between Galaxies

[PART 1 of 2]
In a world where anything is possible the known and the unknown. A science experiment went wrong outer space on one of earths satellite. It exploded and sent the astronauts flying in space. But little did they knew that explosion opened a portal to another galaxy. And the satellite pieces went through and destroyed half a planet.
The few survives of the blast came back to earth not knowing there experiment not just only failed but opened a portal. A few months has passed since the incident and everything was normal. Until the earths atmosphere opened up with a unknown spaceship attacking earth.