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This is both a very obvious and a very interesting proposal: locate an apparent source of gravitation by observing the gravitational effects it has upon a fleet

by qubex 6y ago

This is both a very obvious and a very interesting proposal: locate an apparent source of gravitation by observing the gravitational effects it has upon a fleet of small (almost point-like) craft. However, there’s something that niggles me. If it’s a primordial black hole that has been captured by the sun, why is it (as far as I understand) apparently in the same plane (ecliptic) as all the other major bodies in the solar system? It makes sense for all planets & cetera to be in the same plane because they all originated in the same swirling (flat) planetary nebula... but a captured object could potentially orbit at any inclination (and, considering how massive it is, I doubt it would be coerced into being coplanar by comparatively minor intersections with light bodies such as those present in the Oort Cloud, which are arranged roughly spherically anyway).

ianai 6y ago
It may have just happened to line up correctly. But gravity is going to pull it toward the center of mass for the whole solar system. If it were too massive to be pulled in like it wouldn’t be the hard to spot phenomenon that it has been to this point.
7373737373 6y ago
If SpaceX can afford to put a car into orbit around the sun as a publicity stunt during rocket testing, I wonder how much this would cost. Edit: Probably around $100MM: https://www.spacex.com/about/capabilities https://www.spacex.com/about/capabilities for the launch, several $100MMs for the (space based?) accelerator and spacecraft, and then a few more for operations and research. Yeah, $1 billion as described in the article seems like a good estimate: https://arxiv.org/pdf/1805.01306.pdf https://arxiv.org/pdf/1805.01306.pdf Since knowledge arising from this experiment will probably only be useful as a common good, there aren't really incentives for this to happen, unless governments decide to go through with it. NASA's 2020 budget is only $22.6 billion: https://en.wikipedia.org/wiki/Budget_of_NASA https://en.wikipedia.org/wiki/Budget_of_NASA The Apollo program cost $153 billion: https://en.wikipedia.org/wiki/Apollo_program#Costs https://en.wikipedia.org/wiki/Apollo_program#Costs Okay, this thing is ten times further away from the sun (400 AU) than Pluto (40 AU), 80 times the distance of Jupiter from the sun (5 AU), very far. Still, it's much closer than our next closest star, Proxima Centauri, which is 265612 AU away, or over 660 times the distance of Planet 9.
- ramraj07 6y ago
  If we get actual evidence supporting that there could indeed be a black hole within our solar system, that seems like a true opportunity to advance our knowledge of physics. The potential to study a real black hole up close seems worth massive investments given what kind of breakthroughs could he possible from it.
  - lenkite 6y ago
    Also a lovely, future power-source.
    - 7373737373 6y ago
      How would this work?
      - basementcat 6y ago
        Amplified superradiant scattering is one option. https://en.wikipedia.org/wiki/Black_hole_bomb https://en.wikipedia.org/wiki/Black_hole_bomb
      - sbierwagen 6y ago
        If it's rotating, you can extract its rotational energy using the https://en.wikipedia.org/wiki/Penrose_process https://en.wikipedia.org/wiki/Penrose_process Additionally, all black holes constantly emit Hawking radiation https://en.wikipedia.org/wiki/Hawking_radiation https://en.wikipedia.org/wiki/Hawking_radiation Unfortunately for the planet 9 black hole, it only loses mass on balance it's below a certain size, about 0.007 earth mass. Primordial black holes of that size, if they exist, would be quite useful. However, they would be monumentally hard to find: the black hole above would be 62 micrometres in radius, and have an event horizon temperature of 2.93K. Assuming no changes to the cosmic microwave background, this black hole is unstable: it will eventually radiate away all its mass and disappear. You'll be waiting a while for that to happen, at 20 picowatts, it'll take 1.9e35 gigayears to die.
  - codethief 6y ago
whatshisface 6y ago
Disks minimize gravitational potential energy when angular momentum is held constant. Forming solar systems have ways of radiating energy, but they can't really radiate angular momentum. That's why galaxies and solar systems tend to be disk-shaped. The disk shape is very general and comes from fundamental principles, so I don't see why it couldn't continue to apply when one bit of mass in the system just so happens to be a black hole.
- infogulch 6y ago
  Yes but the mechanism that makes the disk form from the general cloud is physical collisions, two "particles" that have opposite inclinations compared to the average hit each other and end up closer to that average plane. But basically nothing can hit a black hole that size so where would it get its momentum from?
  - whatshisface 6y ago
    >But basically nothing can hit a black hole that size Why would that be true? Individual gas molecules manage to disk-ify and turn in to planets, I don't see why a black hole couldn't. This would presumably happen in the early stages of system formation when there was a lot of stuff flying around separately.
    - qubex 6y ago
      Obviously, nothing can ‘hit’ a black hole: anything that does just gets absorbed by it as it falls in. However, more broadly speaking, the angular momentum is conserved, so the result would be more or less the same. However, given the enormous, ridiculous difference of relative masses (and therefore angular momentum) in the case of black holes and some gas particles, I think my initial point stands.
      - whatshisface 6y ago
        The black hole would interact with many gas particles, not just one. How many would be reasonable? Well, Jupiter is a gas giant and it had to form somehow. Yes, conservation of momentum is the right way to think about that.
beamatronic 6y ago
It’s the shotgun approach to detecting gravity, literally
jayd16 6y ago
Could such a black hole have influenced the current orbiting plane or do we believe it was captured too late?
- qubex 6y ago
  Above he mentions that “if it were there from the start it would obey the same rules”... so I guess he does... though where evidence for this comes from isn’t clear from me (unless it’s some kind of circular logic along the lines of “if it is in the same plane then it must have been there from the start, and if the perturbations in the Oort Cloud objects is consistent with an object in the ecliptic plane, then it must be that if t’s a black hole it was captured early on”, or something like that. I dunno, to be honest. I don’t want to appear like I’m a polemicist with an axe to grind and sour grapes, but as I said in my original post... there’s something about this whole thing that just confuses me a bit.
mabbo 6y ago
I wonder if the influence of the rest of the solar system wouldn't impact it. Consider: the reason we think there is anything out there is because we see a lot of bodies that aren't following the expected pattern. For every action, there is an equal and opposite reaction, so perhaps those out-of-order bodies also pulled Planet 9 closer to the standard plane. Repeat a few billion times over a few billion years, each little tug moving it more in-line (and the rest of the solar system out-of-line). This still depends on it starting relatively close to the same plane, but there may be selection bias involved. Those bodies that met with the solar system and weren't aligned well with the plane may have been more likely to escape again. The one (or ones) remaining are the ones that were well-aligned.

by qubex 6y ago

ianai 6y ago

It may have just happened to line up correctly. But gravity is going to pull it toward the center of mass for the whole solar system. If it were too massive to be pulled in like it wouldn’t be the hard to spot phenomenon that it has been to this point.

7373737373 6y ago

If SpaceX can afford to put a car into orbit around the sun as a publicity stunt during rocket testing, I wonder how much this would cost. Edit: Probably around $100MM: https://www.spacex.com/about/capabilities https://www.spacex.com/about/capabilities for the launch, several $100MMs for the (space based?) accelerator and spacecraft, and then a few more for operations and research. Yeah, $1 billion as described in the article seems like a good estimate: https://arxiv.org/pdf/1805.01306.pdf https://arxiv.org/pdf/1805.01306.pdf Since knowledge arising from this experiment will probably only be useful as a common good, there aren't really incentives for this to happen, unless governments decide to go through with it. NASA's 2020 budget is only $22.6 billion: https://en.wikipedia.org/wiki/Budget_of_NASA https://en.wikipedia.org/wiki/Budget_of_NASA The Apollo program cost $153 billion: https://en.wikipedia.org/wiki/Apollo_program#Costs https://en.wikipedia.org/wiki/Apollo_program#Costs Okay, this thing is ten times further away from the sun (400 AU) than Pluto (40 AU), 80 times the distance of Jupiter from the sun (5 AU), very far. Still, it's much closer than our next closest star, Proxima Centauri, which is 265612 AU away, or over 660 times the distance of Planet 9.

ramraj07 6y ago
If we get actual evidence supporting that there could indeed be a black hole within our solar system, that seems like a true opportunity to advance our knowledge of physics. The potential to study a real black hole up close seems worth massive investments given what kind of breakthroughs could he possible from it.
- lenkite 6y ago
  Also a lovely, future power-source.
  - 7373737373 6y ago
    How would this work?
    - basementcat 6y ago
      Amplified superradiant scattering is one option. https://en.wikipedia.org/wiki/Black_hole_bomb https://en.wikipedia.org/wiki/Black_hole_bomb
    - sbierwagen 6y ago
      If it's rotating, you can extract its rotational energy using the https://en.wikipedia.org/wiki/Penrose_process https://en.wikipedia.org/wiki/Penrose_process Additionally, all black holes constantly emit Hawking radiation https://en.wikipedia.org/wiki/Hawking_radiation https://en.wikipedia.org/wiki/Hawking_radiation Unfortunately for the planet 9 black hole, it only loses mass on balance it's below a certain size, about 0.007 earth mass. Primordial black holes of that size, if they exist, would be quite useful. However, they would be monumentally hard to find: the black hole above would be 62 micrometres in radius, and have an event horizon temperature of 2.93K. Assuming no changes to the cosmic microwave background, this black hole is unstable: it will eventually radiate away all its mass and disappear. You'll be waiting a while for that to happen, at 20 picowatts, it'll take 1.9e35 gigayears to die.
- codethief 6y ago

whatshisface 6y ago

Disks minimize gravitational potential energy when angular momentum is held constant. Forming solar systems have ways of radiating energy, but they can't really radiate angular momentum. That's why galaxies and solar systems tend to be disk-shaped. The disk shape is very general and comes from fundamental principles, so I don't see why it couldn't continue to apply when one bit of mass in the system just so happens to be a black hole.

infogulch 6y ago
Yes but the mechanism that makes the disk form from the general cloud is physical collisions, two "particles" that have opposite inclinations compared to the average hit each other and end up closer to that average plane. But basically nothing can hit a black hole that size so where would it get its momentum from?
- whatshisface 6y ago
  >But basically nothing can hit a black hole that size Why would that be true? Individual gas molecules manage to disk-ify and turn in to planets, I don't see why a black hole couldn't. This would presumably happen in the early stages of system formation when there was a lot of stuff flying around separately.
  - qubex 6y ago
    Obviously, nothing can ‘hit’ a black hole: anything that does just gets absorbed by it as it falls in. However, more broadly speaking, the angular momentum is conserved, so the result would be more or less the same. However, given the enormous, ridiculous difference of relative masses (and therefore angular momentum) in the case of black holes and some gas particles, I think my initial point stands.
    - whatshisface 6y ago
      The black hole would interact with many gas particles, not just one. How many would be reasonable? Well, Jupiter is a gas giant and it had to form somehow. Yes, conservation of momentum is the right way to think about that.

beamatronic 6y ago

It’s the shotgun approach to detecting gravity, literally

jayd16 6y ago

Could such a black hole have influenced the current orbiting plane or do we believe it was captured too late?

qubex 6y ago
Above he mentions that “if it were there from the start it would obey the same rules”... so I guess he does... though where evidence for this comes from isn’t clear from me (unless it’s some kind of circular logic along the lines of “if it is in the same plane then it must have been there from the start, and if the perturbations in the Oort Cloud objects is consistent with an object in the ecliptic plane, then it must be that if t’s a black hole it was captured early on”, or something like that. I dunno, to be honest. I don’t want to appear like I’m a polemicist with an axe to grind and sour grapes, but as I said in my original post... there’s something about this whole thing that just confuses me a bit.

mabbo 6y ago

I wonder if the influence of the rest of the solar system wouldn't impact it. Consider: the reason we think there is anything out there is because we see a lot of bodies that aren't following the expected pattern. For every action, there is an equal and opposite reaction, so perhaps those out-of-order bodies also pulled Planet 9 closer to the standard plane. Repeat a few billion times over a few billion years, each little tug moving it more in-line (and the rest of the solar system out-of-line). This still depends on it starting relatively close to the same plane, but there may be selection bias involved. Those bodies that met with the solar system and weren't aligned well with the plane may have been more likely to escape again. The one (or ones) remaining are the ones that were well-aligned.