"It could be if such a planet exists but I simply don't know."

But in 2007, an island region of stability was reported where a fourth planet could exist.

I don't believe that the planet actually exists, but I like the idea of it a lot.

But if such planets exist, they are likely to be separated from each other by many thousands of light years.

But so far we don't even know if any planet exists for them to live on.

Perhaps the planet does not even exist any longer.

He was in a time where the planets did not yet exist.

It was later revealed, however, that this planet does not exist.

But when the 2 planets exist in different times, they can very well seem to occupy the same place.

For all I know, this entire planet and star system may not even exist in the twenty-fourth century.