Planet Nine... Could it be a planetary-mass black hole?

[JMBuilder]

So if there really is a ninth planet out there, it seems like we would have found it by now. However, there is a theory about the existence of "micro black holes." Could "Planet Nine" be one of these planetary-mass black holes? It would explain why we haven't found anything since micro black holes would be, at most, a few meters in size.

[Darvince]

The reason we haven't found it is because it's so incredibly far away. Unlike planets in other star systems, we have to find ones in our own solar system through direct imaging, which is incredibly difficult compared to the other methods we use to find exoplanets, including transits and radial velocity. And with its mass constrained to around that of Neptune, it should not glow and as it is so far away from the Sun, would as a result be very dim and hard to spot.

[Gregory]

It's very unlikely, as black holes are remnants of stars greater than 10 sun masses that gone supernova, and it's very unlikely we'll ever have a black hole in our solar system, so if Planet 9 exists, it's more likely a planet than a black hole.

There are some dark exoplanets NASA found out there, the darkest being TrES-2b, which recieves almost no light from its star, making it the darkest planet ever found.

So Planet 9 could be one of those dark planets similar to TrES-2b, but smaller, which could explain why we couldn't find it, and has an almost Uranian mass affecting the orbits of dwarf planets without it being a micro black hole.

Besides, Scientists believe it has a radius comparable to that of Neptune.

[atomic7732]

The reason we haven't found it is because it's so incredibly far away. Unlike planets in other star systems, we have to find ones in our own solar system through direct imaging, which is incredibly difficult compared to the other methods we use to find exoplanets, including transits and radial velocity. And with its mass constrained to around that of Neptune, it should not glow and as it is so far away from the Sun, would as a result be very dim and hard to spot.

It's also supposed to be located in an area of the sky where the Milky Way is, and at aphelion, (where it spends most of its time) which makes it that much harder to find. We likely would have found it if it wasn't located on that part of its orbit.

[Darvince]

what if it's invisible right now because it's in front of a nebula or other glowy thing

[JMBuilder]

what if it's invisible right now because it's in front of a nebula or other glowy thing

Wouldn't it leave a visible silhouette?

[atomic7732]

unless it's a bright nebula, it's still reflecting light so it will be of similar brightness, but if it varies even a little our techniques wouldn't really have a problem finding it i don't think

[emarksmi]

Gravitationally it could be a planetary mass black hole, but practically it is much more likely to be a plain old planet.  It is just very far away and VERY dim.