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

Same reason it’s easy to see when the basement light is in when standing at the top of the stairs but difficult to find the cat in the dark when the light is off.