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?
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Those stars radiate light that hit our earth. Planets, don’t normally radiate light (they do a bit depending on if there’s heating in the core for example) like stars that radiate light because of nuclear fusion.
So simply put, whatever planet might exist is probably very dark and far enough away that we wouldn’t be able to detect much anything else. While stars can’t help but to radiate light and show us where they are as long as we’re in the direction their light is traveling.
We should be able to physically see an object like that, but we dont really know where to look. The search area is absolutely massive and we dont have a ton of telescope time to dedicate to the project
Stars are billions of times brighter than planets (actually way more than that), and also orders of magnitude bigger, so it more than makes up for the greater distance.
An analogy for your question would be something like:
**”If I can see a car’s headlights from a over mile away, why can’t I confirm whether there’s a black rock the size of a golf ball 100 feet away from me in a field at night?**”
Because it’s small and not radiating light. Planets are essentially dark rocks on a black background. Stars are easier to see because they’re gigantic and made of white hot glowing plasma.
Stars glow, planets don’t. It’s easy to count lightning bugs in the pitch black darkness (at least if they don’t move) but it’s hard to count trees.
Like others have stated. It’s easier for us to observe and measure a object outputting energy (light) emission than an object absorbing that energy.
Because you can pick pretty much any direction to look and there will be stars. With Planet 9 you have to know *exactly where to look* to see it and we don’t. It’s sort of like the difference between “find any one person in New York City” and “find this one specific person in New York City.” Add to that the relative dimness others have mentioned and the fact that a lot of the equipment that’s spotting distant stars can’t adequately focus on much nearer and dimmer things.
The orbits of planets around the sun can be calculated and a long time ago deviations were detected. These deviations can be attributed to other planets having a gravitational effect on the known orbits and a hunt for such uknown planets started and some were discovered.
Today, as we are making measurements more and more accurately, smaller and smaller deviations are detected, which might be caused by still unknown planets, but might also be caused by completely other things.In order to determine why they are caused, you need to detect the *thing* that is the cause.
The difference in difficulty for detecting objects in space between those that emit light and those that don’t has already been explained.
Even if you did detect there was some kind of object floating in space around our sun, you still have the difficulty of determining if it is a planet or not. In order to be called a planet it has to satisfy certain conditions.
[https://en.wikipedia.org/wiki/Definition_of_planet](https://en.wikipedia.org/wiki/Definition_of_planet)
[https://en.wikipedia.org/wiki/IAU_definition_of_planet](https://en.wikipedia.org/wiki/IAU_definition_of_planet)
It might takes years of observations, or even space missions, to determine if something falls into the planet category or not.
Ex: We know “pluto” exists, and it used to be a planet, but it has lost its status of being a planet a while ago.
Most people have spoken about how it’s easier to detect stars than planets, which is correct, but I’m gonna go in a different direction.
It’s different to prove the existence of a star than prove the non existence of a planet. It is almost impossible to collect all the evidence that we would require to, 100%, without a shadow of a doubt, prove the non existence of a planet. It’s basically proving a negative, which is fundamentally either impossible or incredibly hard.
If at some time we do detect a 9nth planet all that will do is that we will then ask “But is there a 10nth planet?”
Stars very very very bright.
Planets not so bright.
Looking proof of existence is easy.
Looking for proof of non-existence is hard.
Incomplete mathematical interpretations of physics and gravity, and how they affect us and our solar-system make everything guesses until we have either, 1. More sensors out there, or 2. Understand gravity and the dark matter problem more.
Also!!! Big space telescope points in the same direction for a very long time to get those photos! You can’t do the same thing for things moving so much faster in our own solar system.
It’s the middle of a pitch-black, moonless night. You’re in the middle of a large, empty field. There’s a lit flashlight lying on the ground 200 meters away from you, which shines brightly in the darkness. There’s also a small black ball lying in the grass, within 5 meters of you, but it’s dark, and it’s black, and you can’t see it at all.
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