Mars
My planet is Earth. Earth's closest star is the Sun.
"to earth" is the prepositional phrase in the sentence.
It is "closest to."
The star closest to Earth is the sun. The phrase "... largest to planet Earth ... " is meaningless.
The sun
Mars
Perigee
The closest planet to the Sun is Mercury, followed by Venus and then Earth.
The planet that's able to come closest to Earth is Venus. The next one after Venus is Mars.
After the sun it's Proxima Centauri
The comet that came closest to Earth in 1997 was Comet Hale-Bopp. It reached its closest approach to Earth in late March of that year, becoming one of the brightest comets visible from Earth in the twentieth century.
the moon is the closest to the earth