What does this sentence mean?

It's rapidly becoming the little planetoid that could, with more satellites than the inner four planets put together.

( From an article on the dwarf planet Pluto. To check it, click on this link.)

What does that '' that could '' part indicate?

I think it's a reference to "The Little Engine That Could" - I've never read the book, but from what I've heard, everyone is dismissive of the little engine but it proves itself in the end. Here, Pluto's no longer got planet status, and yet it's got more satellites than most planets.

I think it's a reference to "The Little Engine That Could" - I've never read the book, but from what I've heard, everyone is dismissive of the little engine but it proves itself in the end. Here, Pluto's no longer got planet status, and yet it's got more satellites than most planets.