Why we can accurately detect stars billions of light years away, but we can’t confirm if we have a 9th planet in our solar system?

Question

Why we can accurately detect stars billions of light years away, but we can’t confirm if we have a 9th planet in our solar system?

In: 2123

Answer 1

My understanding is that you don’t generally see individual stars that far away unless something exceptional is happening (the star is crazy massive, there is gravitational micro lensing, it’s a variable star, it’s exploding, etc.)