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It’s possible, but we’ve yet to directly detect anything. Out beyond Neptune is a vast and dark amount of space. Finding even large planets out that far would be difficult with our current technology.

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Its theorized based on some math, but also space is big and difficult.

At this point, the answer is "probably not".

There's been a bunch of math and predictions to indicate there might be, it's possible, but every time someone says they've figured out where it is, where it should be, it.... isn't.

At this point, it's hard to imagine missing anything significant, or at least, anything significant that reflects light, like a planet would.

A small, stellar black hole, however, could easily remain undetected directly while still showing up regularly and frustratingly in our math. Is it likely? No, not at all. But it's possible, and that's fun, the idea that we might have a black hole orbiting our sun beyond Neptune is a fun one.

You mean planet X I guess, there's evidence for it based on the way other objects are having their orbits affected, but we haven't actually observed it. Sounds kind of funny to say, but there's a lot of dust in that part of space, it's hard to see anything there.

>Neptune orbits our Sun, a star, and is the eighth planet from the Sun at a distance of about 2.8 billion miles (4.5 billion kilometers).

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>In 2011 Neptune completed its first 165-year orbit since its discovery in 1846.

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where to look?

when do we look there?

Sure it’s a gigantic area, but my logic was that we are discovering exoplanets left and right. Why is it so harder in our own backyard?

We discover exoplanets because they are little black dots in front of a giant field of light.

Finding another planet past Neptune would be looking for a tiny black dot in front of a giant field of black.

Batygin and Brown hypothesised a Neptune-mass object orbiting on a highly eccentric 10,000 - 15,000 year orbit as a solution to an observed "shepherding" of Kuiper belt object orbits (because they observed what looked like a lopsided distribution in their orientations).

As for why it hasn't been observed, if it exists, is that the region it would be in its orbit is huge, as in, dwarfing most of the solar system. That far out, from the planet's perspective the sun would be nearly indistinguishable from other stars, so the planet would be very, very cold and have next to no reflected light.

So you'd be looking for a black needle in a gigantic dark haystack who's only clues about where it is is based off of how other needles you've found have been distributed in the gigantic haystack.

When we find exoplanets, its largely because they blot out the light of their parent star, or in the case of particularly massive planets, they can make their host star wiggle.
With the hypothetical planet 9, we have no host star to helpfully observe and watch for an occultation.

1. beyond Pluto would be very difficult to spot even a big gas giant like Jupiter, as at such distance the translation and the movement across sky is very small to be perceived casually.

2. In the outer Pluto orbit the orbital excentricity may be very pronounced. Imagine that such planet could be anywere, not only in the ecliptic (zodiac area).

3. Excentricity also can put is much distant place for hundred of years.

4. Also the brightness would be smaller than 13rd magnitude, ie. beyond most of amateur telescopes.

So I'm not so confident that we had found anything on the outer solar system. While we had much tech advance on Astronomy, we are still very limited to find things if not by accident.

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> we are discovering exoplanets left and right. Why is it so order in our own backyard?

Discovering exoplanets is sort of like seeing distant mountains, we can spot them because they're "easy" to find by just looking for dips in light from their respective stars.

Discovering a planet near us is like being able to identify a small pebble from far away because we can't use the same methods we use to find exoplanets, so we're just blindly looking into space trying to see if one of the millions of little dots we can see moves like a planet would.

In order to see it we'd need to know exactly where to look. In order to know where to look we need to see it.

If the orbit is eccentric enough then when it's closest to the sun it will be much easier to spot. But that could be centuries from now.

With deep space radio telescopes I think we'd have a good chance of finding any missing planets, could use active radar to scan large sections of the sky.

That also could take centuries though.

There’s a documentary about this on Curiosity Stream “Search for our Suns Lost Planet” it follows a couple leading researchers on the topic. I found it rather insightful :)

I agree it's best to be skeptical here but folks are pinning this alleged planet nine at an apparent magnitude greater than 20/21 That's very faint, even by modern standards. While that's not out of reach in big telescopes, it's time intensive and you'd need to know bang on where to look.

That magnitude is near the limit of most of the ongoing all sky surveys, so it's not particularly surprising that it wouldn't yet show up that way were it to exist. In that respect at least I don't think it's fair to totally rule it out because we don't see it yet. That's way harder than it might initially might seem. Things as far away from the sun as this is proposed to be are going to be really difficult to detect via the ole' photon collection method regardless of size.

This.

Exoplanet hunting is significantly easier because of this. We also know where to look because each star acts as a beacon indicating that there may be planets and the field of view required for detection is minimal. We don't really need to calculate where they may be, we just have to observe in one small spot of the sky for a bit of time and see if the brightness level changes.

Trying to detect another planet around our own sun we could potentially calculate for, but even trying to observe it may be incredibly difficult as it could be a very dark object that doesn't radiate much of anything and if it is passed neptune it is barely receiving any light from our sun. Add in that it technically could be anywhere within sky, more realistically within the 17 degrees all other planets of the sky are within, we still would have to look over huge swaths of the sky to try and find it. A most difficult task indeed.

One way would be to send out two observatories in perpendicular directions then at a sufficient(?) distance, have them look back at the sun and look for unexpected perturbations. Then calculate.

It wouldn't be cheap though...

A related theory was that this hypothetical body was larger than Neptune, potentially a brown dwarf:

https://en.wikipedia.org/wiki/Nemesis_(hypothetical_star)

And most of the Exoplanets are actually found by observing the small doppler (color) shift of the parent star light as the planet tugs the star towards us then away from us, which is why most of the planets found so far are close to their parent stars (means we can find the color/doppler shift with shorter observation times). Since this object would be beyond the orbit of Neptune, its orbit period is longer, thus one would have to make very precise observations over baselines of a century or so to see the signal start to show up in solar observations. We might just be getting close to that threshold now though if someone wanted to try to compile the last century of data and try to correct for all the instrument bias and other sources from the rest of the known solar system. That would only give us the general orbit period and distance though.

there's a lot of stars with planets. you want to find ONE PLANET.

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>Why is it so order in our own backyard?

this covers a patch of sky the size of your thumbnail held at arms length. 10,000 galaxies, each with tens of millions of stars... each of those stars with planets.

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The Hubble Ultra-Deep Field (HUDF) is a deep-field image of a small region of space in the constellation Fornax, containing an estimated 10,000 galaxies.

https://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field

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this covers a patch of sky the size of a grain of sand held at arms length

NASA’s Webb Delivers Deepest Infrared Image of Universe Yet
https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-delivers-deepest-infrared-image-of-universe-yet/

NASA’s James Webb Space Telescope has delivered the deepest and sharpest infrared image of the distant universe so far. Webb’s First Deep Field is galaxy cluster SMACS 0723, and it is teeming with thousands of galaxies – including the faintest objects ever observed in the infrared.

THIS. It's a BIG search area because things are further away from each other that far out and thus the gravity perturbations on the other planets and small bodies is small. Small effect means we only know the general area it's in. Couple that with the dim lighting that far away from the sun and it means you have to stare for a long time to see the dim objects, and thus it takes longer to search that part of the sky with enough sensitivity to see things this dim.

Also a reminder that we don't know everything about the universe or physics yet! While Planet 9 would be a cool find, it always makes me think of Vulcan: the "planet" they used to explain Mercury's orbit with Newtonian physics.

With this object being so far away, and a possible 10,000 year orbit, it would take a long long long time to make out perturbations due to it.

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There could also be a huge planet way out near the oort cloud. With an orbital period in the thousands of years and a temperature near the background, it might take a tremendous stroke of luck to find it before we have a flotilla of Webb class space telescopes dedicated to the topic of outer solar system objects.

Man, the incomprehensible size of space never ceases to amaze me..

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Spotting a "small" dark object against bright stars - which will necessarily be at a fantastic distance - isn't going to be easy. Even if it turns out to be closer to the size of Neptune than Pluto.

Not gonna lie, 'Nemesis' is a hell of a name for it.

Well, the large amount of objects in the kuiper belt and beyond could explain the eccentric orbits of kuiper belt objects. It's pretty hard to say without sending a ship out there.

Because to find it you need money, probes and space.

We barely have managed to send robots on mars. Maybe one day when people build telescopes that orbit pluto, we might know.

We can’t find it with the Hubble or James Webb lol? Although to my understanding the James Webb is infrared or something

Its hard because of lack of light

Then we should hurry up and start it...

A small stellar sized black hole would be on the order of at least 3 solar masses. It would mean that we were part of a binary system with a supernova or somehow the solar system captured a rogue black hole. I’m not an astrophysicist but I‘m not sure what the orbital dynamics of that scenario would entail. I’m assuming you’re actually referring to a primordial black hole, something formed during the Big Bang, which could theoretically have smaller masses?

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If you look at the recent exoplanet photography, you will see, in some cases, planets much farther from their stars than Neptune and big giants.

Also there is the interestelar space, and gravity bound stars... even brown dwarfs can be there, while it couls be a great gravital issue. Who can say what there is there?

I mean, it's not my theory, I'm most certainly not an astrophysicist either, so it could well be a primordial one, sure. I think the documentary in which I saw it mentioned, and I couldn't tell you the name, they're my background noise, the idea that it was captured as opposed to native to our solar system.