Here's why:

* Stars are massive: Stars are giant balls of hot gas that produce light and heat through nuclear fusion. This process requires immense gravity, which is only possible with a huge mass. Even the smallest stars are still much larger than Earth.

* Minimum mass for nuclear fusion: For a star to ignite and sustain nuclear fusion, it needs to have a certain minimum mass. This minimum mass is around 75 times the mass of Jupiter, which is still much larger than Earth.

However, there are objects called brown dwarfs:

* Brown dwarfs: These are objects that are larger than planets but not massive enough to ignite nuclear fusion like stars. Some brown dwarfs can be roughly the size of Jupiter, which is much smaller than a typical star but still larger than Earth.

In summary: While there are no stars as small as Earth, there are objects like brown dwarfs that are larger than planets but smaller than stars, and some can be about the size of Jupiter.