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

whats easier to see, a 100000 watt searching light at 1 km or a black 1 cm stone at 10 meters distance.

All in the dark