The first planet in the solar system is Mercury
Mercury is the first planet in our solar system.
The first planet in our solar system is Mercury.
Because that is how the Solar system formed.
Not in my solar system.
The earth, along with the rest of the solar system, was formed approximately 4.5 billion years ago.
The planet that is closest to the sun is Mercury.
It's highly unlikely that Jupiter was the first planet. There's no evidence that Jupiter formed any earlier than other planets in our solar system, and no reason at all to believe that planets in other older solar systems might not have formed long ago.
Jupiter
It's not the first planet of the universe, it's the first planet in the solar system.
The planets must all have formed at approximately the same time.
When the Moon was formed, the Solar System WAS already a solar system.