Most of the planets are orphans without parent stars.

We always think that planets are orbiting their parent stars. But the reality seems very different. Researchers think, that most of the planets in the universe are orphan or rogue planets. Rogue planets are traveling in the universe until some star catches them. There is the possibility that somewhere in history rogue planet traveled through the young solar system. And that thing caused the disastrous gravitational effect in our solar system. 

Rogue planets are still a threat to our solar system. Some of those rogue planets are heavy rocky planets and if the planet with four Earth masses will travel through our solar system we would be in trouble. There are theories that maybe Uranus or even Earth were once rogue planets. The strange posture of Uranus supports the theory that the origin of that planet was somewhere else than in our solar system. 

Snowball-Earth theory (The Precambrian extinction)

 But the argument against that is in the case of Earth. Is the position of the Earth similar to other planets? The fact is that the Earth might be changed its position in our solar system. Or maybe the Sun stole young Earth from another star. Snowball-Earth was happening in the Precambrian era. 

But there is also the possibility that the trajectory of Earth turned extremely oblong. That caused the major parts of the Earth covered under the ice. There was also open water near the equator. Period of this period was in Cryogenian period about  720 to 635  million years ago

And the evidence about the snowball Earth is the thing that supports the theory that maybe Earth was once far from the Sun. Some other theories explain the cold era as the change in the climate. 

But was Earth sometimes in farther past rogue planet? This thing is a nice hypothesis. But it doesn't mean to form of life. And that period could be only a short time in the history of Earth. 

https://bigthink.com/starts-with-a-bang/most-planets-are-orphans/

https://www.newdinosaurs.com/the-precambrian-era

https://en.wikipedia.org/wiki/Cryogenian

https://en.wikipedia.org/wiki/Snowball_Earth

https://en.wikipedia.org/wiki/Precambrian

Image: https://bigthink.com/starts-with-a-bang/most-planets-are-orphans/

https://thebrightchronicle.blogspot.com/