Could there be another planet between Mercury and the Sun? Could there be another planet between Mercury and the Sun?
Kepler found a lot of planets orbiting its star even 20 times closer than Mercury.
If there were such planets in our system - would it be possible to discover them?
It is very unlikely. While the hypothetical planet Vulcan between Mercury and the Sun was ruled out many decades ago searches for Vulcanoid asteroids would very likely have detected anything that might qualify as a intra-Mercurial planet.