I've encountered arχiv before but reading it written out with the chi symbol made it finally click for me. For some reason I've been mentally pronouncing it ark-sieve. A Homeresque moment for myself.
I've encountered arχiv before but reading it written out with the chi symbol made it finally click for me. For some reason I've been mentally pronouncing it ark-sieve. A Homeresque moment for myself.
Looks promising. But ultimately, the only thing that will matter is actually finding the damn thing. Models, no matter how advanced, are still just models. They're all based on certain assumptions...
Looks promising. But ultimately, the only thing that will matter is actually finding the damn thing. Models, no matter how advanced, are still just models. They're all based on certain assumptions that could always prove wrong. We have enough model evidence at this point to suggest Planet 9 is a strong possibility, and the only real next stop is actually finding the damn thing.
That is much, much easier said than done. The baseline these researchers used for their simulations assumes a semi-major axis of 500 AU, an eccentricity of 0.25, and an inclination of 20 degrees....
That is much, much easier said than done. The baseline these researchers used for their simulations assumes a semi-major axis of 500 AU, an eccentricity of 0.25, and an inclination of 20 degrees. So not only is their best guess at its location 10 times further from the sun than Pluto, it's also in a far less circular orbit than the other planets and tilted way out of the ecliptic. And it's only 5 earth-masses. And those are all still just guesses. Studies like these are really important for justifying and informing the search for this needle in the spatial haystack.
Yep. That said, one of my professors, when Mike Brown initially publicly announced the existence of the planet seven years ago, told us that there was no doubt in his mind about it because Prof...
Yep. That said, one of my professors, when Mike Brown initially publicly announced the existence of the planet seven years ago, told us that there was no doubt in his mind about it because Prof Brown is just that good at what he does. He's the guy who found so many dwarf planets that they had to demote Pluto.
But is there any evidence that this is actually a honest-to-god planet? If it's that far out, my guess is that there's so much crap floating about out there that calling this one a planet is about...
But is there any evidence that this is actually a honest-to-god planet? If it's that far out, my guess is that there's so much crap floating about out there that calling this one a planet is about as loose of a decision as calling pluto one. Or is it that Planet 9 is hypothesized to exist in a part of space that is otherwise mostly empty? Some cursory reading suggests there's a noisy band (Kuiper belt) 30-50 AU out (which is pretty much Plutos orbital parameters) and the oort cloud (also only hypothesized) is supposed to be 2000 AU out. That'd suggest that the 50-2000 band is... almost empty? Though I guess once we start looking with adequate tools, we'll probably find a lot of stuff there? I'd certainly call it a stretch to call P9 a planet, when we don't know yet whether its orbital track is at all cleared out.
While there's no exact number1 associated with the mass required for a body to clear its orbit, something with a mass of 5 Earths would almost certainly qualify, even at 500 AU. For reference,...
While there's no exact number1 associated with the mass required for a body to clear its orbit, something with a mass of 5 Earths would almost certainly qualify, even at 500 AU. For reference, Pluto (dwarf planet) is 0.0025 Earth-masses and Mercury (planet) is 0.0553 Earth-masses.
1. There have been criteria put forward, however. If you use the method that doesn't require any empirical data, Jean-Luc Margot's Π, you get a Π-value of 3.3 for the parameters listed in the paper which is well above the Π=1 required to clear the neighborhood. Pluto has a Π-value of 0.028
Hmm. I do wonder if these somewhat empirical formulae generalize out to 500AU. My hunch is that out there orbits are so slow that interactions are so rare that clearing the orbit just doesn't...
Hmm. I do wonder if these somewhat empirical formulae generalize out to 500AU. My hunch is that out there orbits are so slow that interactions are so rare that clearing the orbit just doesn't happen nearly as much. The exponent of a (9/8) is a bit too low to convince me that this is accurately reflected. Orbits just get mindnumbingly slow out there, much slower than a^(9/8). But I'm going to refrain from backseat sciencing when I'm not qualified to know whether there's other factors they have considered that would imply a large a also helps with clearing the orbit or something...
Orbital period is super easy to calculate, it's just a^3/2 if you're using Astronomical Units. At 500 AU that's only about 11,000 years, which may be mind-numbingly slow on a human time scale but...
Orbital period is super easy to calculate, it's just a^3/2 if you're using Astronomical Units. At 500 AU that's only about 11,000 years, which may be mind-numbingly slow on a human time scale but in a cosmic sense it's nothing.
Right, but I'd expect there to be combinatorial-ish compounding effects. Not only P9 is so slow, its competitors are too, so if the points where the orbital ellipses are sufficiently close are...
Right, but I'd expect there to be combinatorial-ish compounding effects. Not only P9 is so slow, its competitors are too, so if the points where the orbital ellipses are sufficiently close are short (inclination), then the odds of meeting that competitor there decrease.... quadratically??? Meanwhile, the added mass increases the "danger zone" by a small margin, nowhere near enough to compensate for the addition of so much more space.
Again, I'm probably neglecting second-order effects here. Sadly the data is just not there right now to actually satisfy my curiosity.
Sure, there may be random shit, but it would be really weird if there were 5 Earth masses worth of random planetoids in the same spot in the same orbit.
Sure, there may be random shit, but it would be really weird if there were 5 Earth masses worth of random planetoids in the same spot in the same orbit.
I'm not saying this Planet 9 is just 5 earth masses of asteroids in a trench coat. If the paper is accurate, it's likely one big "dwarf planet". Question is, considering we know so little about...
I'm not saying this Planet 9 is just 5 earth masses of asteroids in a trench coat. If the paper is accurate, it's likely one big "dwarf planet". Question is, considering we know so little about this region: Is there likely to be little enough other crap (beyond the 5 earth masses that the research identified) in its general vicinity to suggest it's actually a planet, and not just a "improper" planet like pluto? Like, orbital periods out there are so freakishly long, the law of "if something intersected the orbit of this planet, it was probably yeeted or collided with at some point in the past" doesn't really apply. So there could be a lot of other stuff out there intersecting its orbit, meaning it's not a planet.
Yes, it would need to be something big enough to cause orbital resonances (objects orbiting with repetitive periods, like how Neptune orbits three times for every two orbits Pluto makes or how...
Yes, it would need to be something big enough to cause orbital resonances (objects orbiting with repetitive periods, like how Neptune orbits three times for every two orbits Pluto makes or how every four trips Io takes around Jupiter, Europa takes two trips and Ganymede takes one).
For example, if you spot three grains of sand in a 4:5:6 orbital resonance, you can assume there must be something else causing them to orbit in that way because they are too small to significantly influence each other's orbits. So perhaps there is a planet that you can't see that would create a 3:4:5:6 orbital resonance with the grains of sand.
It would be nearly impossible to do it with probes due to orbital physics and fuel costs. It will also be really hard to the point you could call it "nearly impossible" with telescopes because...
It would be nearly impossible to do it with probes due to orbital physics and fuel costs. It will also be really hard to the point you could call it "nearly impossible" with telescopes because it's so distant and dim and there's such a huge amount of the sky that needs to be searched, but at least it is actually feasible to find it using telescopes.
Best shot at using telescopes here is probably synthetic apertures. Build a large amount of mediocre telescopes, spread them as far apart as you can and use beamforming math to correlate their...
Best shot at using telescopes here is probably synthetic apertures. Build a large amount of mediocre telescopes, spread them as far apart as you can and use beamforming math to correlate their measurements. The number-crunching is probably a pain, but it's easier than building an asteroid-sized telescope.
You're talking about interferometry, not synthetic apertures, although that would be an accurate name for a telescope array if the name wasn't already taken. I'm not enough of an expert on Solar...
You're talking about interferometry, not synthetic apertures, although that would be an accurate name for a telescope array if the name wasn't already taken.
I'm not enough of an expert on Solar System astronomy to respond to that definitively, but I would suspect Planet 9 wouldn't have much of a radio signal, so a mid-Infrared telescope would likely be best, and, thankfully, that is exactly what James Webb is best at exploring. Unfortunately for Planet 9 research, JWST will likely be spending more time looking at black holes and galaxies on the other side of the Observable Universe, so it will be harder to dedicate time to this search specifically, although it's always possible that Planet 9 will be found by chance when looking at those images. I've never conducted serious astronomical research beyond undergraduate projects, but I would suspect we already have enough images to prove the existence of Planet 9; the issue is just that we would need to dig through the countless images searching for the faintest changing pixels.
Webb is exactly the wrong telescope for something like this, it has a very small field of view – more akin to a telephoto lens. What you need to find a planet is a survey telescope. I believe WISE...
Webb is exactly the wrong telescope for something like this, it has a very small field of view – more akin to a telephoto lens. What you need to find a planet is a survey telescope. I believe WISE did briefly search for Planet 9 and came up empty, but that was only a 16-inch mirror. The upcoming Roman Space Telescope is also an infrared survey telescope and has a much better chance of finding something with its nearly 8-foot primary mirror.
Yes, I clearly wasn't thinking very thoroughly about it. Of course a survey would be the best way to discover things in unknown locations. That should have been obvious to me. JWST will be "great"...
Yes, I clearly wasn't thinking very thoroughly about it. Of course a survey would be the best way to discover things in unknown locations. That should have been obvious to me. JWST will be "great" once we have somewhere specific to look. Of course, it will still be giving us images of a quality pretty similar to those that Hubble gave us of Pluto before New Horizons visited.
Via Wikipedia:Aperture Synthesis: "Aperture synthesis or synthesis imaging is a type of interferometry" Jokes aside, it's basically the same. A synthetic aperture radar is...
Via Wikipedia:Aperture Synthesis: "Aperture synthesis or synthesis imaging is a type of interferometry"
They're the same picture.
Jokes aside, it's basically the same. A synthetic aperture radar is interferometry-through-time using a single sensor.
but I would suspect Planet 9 wouldn't have much of a radio signal,
Right. We're starting to see work on optical aperture synthesis, but because of the tiny wavelength that's a bitch to get right. Meanwhile in radio astronomy you can easily beamform offline because you can record individual oscillations of the signal. Maybe we'll see offline beamforming for optical sensors at some point. That would mean you can do SAR stuff in the optical range, where P9 really ought to have a signal. For radio, I think that's unlikely to be the case.
Or to be really silly, active radio astronomy? But that's probably only viable if you already know where to look. And the target isn't 70 light hours away. Then again, who knows what kind of resolution you can get out of weak signals if you've got 2000 AESA transceivers spread across earth's orbit around the sun.
Regardless, I don't think we'll be confirming that this sucker cleared its orbit until we've got better sensors.
Maybe we can send a fleet of Global Hawks into the outer Solar System to conduct a survey. But yeah it's insane the precision you need for optical interferometry because the cameras would have to...
Maybe we can send a fleet of Global Hawks into the outer Solar System to conduct a survey.
But yeah it's insane the precision you need for optical interferometry because the cameras would have to be within something like a quarter of a wavelength of alignment, which would be about 100 nanometers. Just another really cool concept that I'll have to leave to the experts because I will never have the patience to fully understand the underlying engineering.
One thing I wonder is, what if it was once there, but is no longer? Stars form in tight clusters, and planets in extremely wide obits like that are the most easily disrupted by close stellar...
One thing I wonder is, what if it was once there, but is no longer? Stars form in tight clusters, and planets in extremely wide obits like that are the most easily disrupted by close stellar encounters. Things that far out aren't held on to that tightly. Let's say Planet IX did exist at the beginning of the Solar System, influenced the orbits of all these Kuiper Belt objects, but then was later ripped away by another star passing close to the Sun ("close" on interstellar distances.) Would the patterns we observe in the orbits of KBOs still remain, or would they drift with time? Recent surveys suggest that something like half or more of planets are interstellar, not bound to any star. Most of these rogue planets likely formed around stars and were later torn from their orbits by close stellar encounters. It's not impossible that Planet IX did exist, set up the orbits of the KBOs, and was later torn away by a passing star when it was way out at its Aphelion. But I wonder if the effects we observe in the KBO populations would still remain, even if the planet that formed those patterns was torn away several billion years ago.
First, the Solar System is only a few billion years old, not several (not a huge distinction, but it can be meaningful depending on your definition of "several"). More importantly, though, over...
First, the Solar System is only a few billion years old, not several (not a huge distinction, but it can be meaningful depending on your definition of "several").
More importantly, though, over billions of years, the effects of the planet would be erased by the gravity of other planets, not to mention the likelihood that a star coming through and ejecting Planet 9 would likely fuck up the orbits of the planetoids out there. The orbits are (hypothesized to be) caused by harmonic resonances with the orbit of Planet 9 and outer-Solar System planets, so if you get rid of the Planet, you get rid of the resonances keeping them in place.
This is the process for finding the damn thing. IIRC, Neptune and Pluto where theorized to exist before we actually observed them. It's through these methods that we can hope to find such a dark,...
This is the process for finding the damn thing. IIRC, Neptune and Pluto where theorized to exist before we actually observed them. It's through these methods that we can hope to find such a dark, far planet.
One of the authors of the paper walks everyone through it and answers a lot of questions about it in this episode of Event Horizon. This is conclusive. There is something larger than any of the...
Exemplary
One of the authors of the paper walks everyone through it and answers a lot of questions about it in this episode of Event Horizon. This is conclusive. There is something larger than any of the inner planets out there and that question is now settled with hard evidence, period. The what and where are the more interesting part, and now we can start looking for it instead of entertaining arguments about if it exists in the first place. It will be an awful lot more easy to get telescope time for this hunt going forward.
They may name it "David Bowie" if for no other reason than all Greek names are already spoken for with other celestial objects.
It’s a consequence of demoting Pluto, that our Solar System has to have nine planets, so a new one will come out from the aether and somehow the science will justify it. The Pizzas must be served!
It’s a consequence of demoting Pluto, that our Solar System has to have nine planets, so a new one will come out from the aether and somehow the science will justify it. The Pizzas must be served!
mild spoilers for the video game referenced Inhabited by *the disembodied souls* of owl people with antlers. The Stranger was almost totally devoid of life, remember?
mild spoilers for the video game referenced
Inhabited by *the disembodied souls* of owl people with antlers. The Stranger was almost totally devoid of life, remember?
Preprint paper from arχiv:
https://arxiv.org/html/2404.11594v1
I've encountered arχiv before but reading it written out with the chi symbol made it finally click for me. For some reason I've been mentally pronouncing it ark-sieve. A Homeresque moment for myself.
or is it Homer-χ...
Looks promising. But ultimately, the only thing that will matter is actually finding the damn thing. Models, no matter how advanced, are still just models. They're all based on certain assumptions that could always prove wrong. We have enough model evidence at this point to suggest Planet 9 is a strong possibility, and the only real next stop is actually finding the damn thing.
That is much, much easier said than done. The baseline these researchers used for their simulations assumes a semi-major axis of 500 AU, an eccentricity of 0.25, and an inclination of 20 degrees. So not only is their best guess at its location 10 times further from the sun than Pluto, it's also in a far less circular orbit than the other planets and tilted way out of the ecliptic. And it's only 5 earth-masses. And those are all still just guesses. Studies like these are really important for justifying and informing the search for this needle in the spatial haystack.
Yep. That said, one of my professors, when Mike Brown initially publicly announced the existence of the planet seven years ago, told us that there was no doubt in his mind about it because Prof Brown is just that good at what he does. He's the guy who found so many dwarf planets that they had to demote Pluto.
But is there any evidence that this is actually a honest-to-god planet? If it's that far out, my guess is that there's so much crap floating about out there that calling this one a planet is about as loose of a decision as calling pluto one. Or is it that Planet 9 is hypothesized to exist in a part of space that is otherwise mostly empty? Some cursory reading suggests there's a noisy band (Kuiper belt) 30-50 AU out (which is pretty much Plutos orbital parameters) and the oort cloud (also only hypothesized) is supposed to be 2000 AU out. That'd suggest that the 50-2000 band is... almost empty? Though I guess once we start looking with adequate tools, we'll probably find a lot of stuff there? I'd certainly call it a stretch to call P9 a planet, when we don't know yet whether its orbital track is at all cleared out.
While there's no exact number1 associated with the mass required for a body to clear its orbit, something with a mass of 5 Earths would almost certainly qualify, even at 500 AU. For reference, Pluto (dwarf planet) is 0.0025 Earth-masses and Mercury (planet) is 0.0553 Earth-masses.
1. There have been criteria put forward, however. If you use the method that doesn't require any empirical data, Jean-Luc Margot's Π, you get a Π-value of 3.3 for the parameters listed in the paper which is well above the Π=1 required to clear the neighborhood. Pluto has a Π-value of 0.028
Hmm. I do wonder if these somewhat empirical formulae generalize out to 500AU. My hunch is that out there orbits are so slow that interactions are so rare that clearing the orbit just doesn't happen nearly as much. The exponent of a (9/8) is a bit too low to convince me that this is accurately reflected. Orbits just get mindnumbingly slow out there, much slower than a^(9/8). But I'm going to refrain from backseat sciencing when I'm not qualified to know whether there's other factors they have considered that would imply a large a also helps with clearing the orbit or something...
Orbital period is super easy to calculate, it's just a^3/2 if you're using Astronomical Units. At 500 AU that's only about 11,000 years, which may be mind-numbingly slow on a human time scale but in a cosmic sense it's nothing.
Right, but I'd expect there to be combinatorial-ish compounding effects. Not only P9 is so slow, its competitors are too, so if the points where the orbital ellipses are sufficiently close are short (inclination), then the odds of meeting that competitor there decrease.... quadratically??? Meanwhile, the added mass increases the "danger zone" by a small margin, nowhere near enough to compensate for the addition of so much more space.
Again, I'm probably neglecting second-order effects here. Sadly the data is just not there right now to actually satisfy my curiosity.
Sure, there may be random shit, but it would be really weird if there were 5 Earth masses worth of random planetoids in the same spot in the same orbit.
I'm not saying this Planet 9 is just 5 earth masses of asteroids in a trench coat. If the paper is accurate, it's likely one big "dwarf planet". Question is, considering we know so little about this region: Is there likely to be little enough other crap (beyond the 5 earth masses that the research identified) in its general vicinity to suggest it's actually a planet, and not just a "improper" planet like pluto? Like, orbital periods out there are so freakishly long, the law of "if something intersected the orbit of this planet, it was probably yeeted or collided with at some point in the past" doesn't really apply. So there could be a lot of other stuff out there intersecting its orbit, meaning it's not a planet.
Yes, it would need to be something big enough to cause orbital resonances (objects orbiting with repetitive periods, like how Neptune orbits three times for every two orbits Pluto makes or how every four trips Io takes around Jupiter, Europa takes two trips and Ganymede takes one).
For example, if you spot three grains of sand in a 4:5:6 orbital resonance, you can assume there must be something else causing them to orbit in that way because they are too small to significantly influence each other's orbits. So perhaps there is a planet that you can't see that would create a 3:4:5:6 orbital resonance with the grains of sand.
Huh, interesting, can we find this planet using different kinds of a telescopes near or on Earth or should we use a spacecrafts?
It would be nearly impossible to do it with probes due to orbital physics and fuel costs. It will also be really hard to the point you could call it "nearly impossible" with telescopes because it's so distant and dim and there's such a huge amount of the sky that needs to be searched, but at least it is actually feasible to find it using telescopes.
Best shot at using telescopes here is probably synthetic apertures. Build a large amount of mediocre telescopes, spread them as far apart as you can and use beamforming math to correlate their measurements. The number-crunching is probably a pain, but it's easier than building an asteroid-sized telescope.
You're talking about interferometry, not synthetic apertures, although that would be an accurate name for a telescope array if the name wasn't already taken.
I'm not enough of an expert on Solar System astronomy to respond to that definitively, but I would suspect Planet 9 wouldn't have much of a radio signal, so a mid-Infrared telescope would likely be best, and, thankfully, that is exactly what James Webb is best at exploring. Unfortunately for Planet 9 research, JWST will likely be spending more time looking at black holes and galaxies on the other side of the Observable Universe, so it will be harder to dedicate time to this search specifically, although it's always possible that Planet 9 will be found by chance when looking at those images. I've never conducted serious astronomical research beyond undergraduate projects, but I would suspect we already have enough images to prove the existence of Planet 9; the issue is just that we would need to dig through the countless images searching for the faintest changing pixels.
Webb is exactly the wrong telescope for something like this, it has a very small field of view – more akin to a telephoto lens. What you need to find a planet is a survey telescope. I believe WISE did briefly search for Planet 9 and came up empty, but that was only a 16-inch mirror. The upcoming Roman Space Telescope is also an infrared survey telescope and has a much better chance of finding something with its nearly 8-foot primary mirror.
Yes, I clearly wasn't thinking very thoroughly about it. Of course a survey would be the best way to discover things in unknown locations. That should have been obvious to me. JWST will be "great" once we have somewhere specific to look. Of course, it will still be giving us images of a quality pretty similar to those that Hubble gave us of Pluto before New Horizons visited.
Via Wikipedia:Aperture Synthesis: "Aperture synthesis or synthesis imaging is a type of interferometry"
Jokes aside, it's basically the same. A synthetic aperture radar is interferometry-through-time using a single sensor.
Right. We're starting to see work on optical aperture synthesis, but because of the tiny wavelength that's a bitch to get right. Meanwhile in radio astronomy you can easily beamform offline because you can record individual oscillations of the signal. Maybe we'll see offline beamforming for optical sensors at some point. That would mean you can do SAR stuff in the optical range, where P9 really ought to have a signal. For radio, I think that's unlikely to be the case.
Or to be really silly, active radio astronomy? But that's probably only viable if you already know where to look. And the target isn't 70 light hours away. Then again, who knows what kind of resolution you can get out of weak signals if you've got 2000 AESA transceivers spread across earth's orbit around the sun.
Regardless, I don't think we'll be confirming that this sucker cleared its orbit until we've got better sensors.
Maybe we can send a fleet of Global Hawks into the outer Solar System to conduct a survey.
But yeah it's insane the precision you need for optical interferometry because the cameras would have to be within something like a quarter of a wavelength of alignment, which would be about 100 nanometers. Just another really cool concept that I'll have to leave to the experts because I will never have the patience to fully understand the underlying engineering.
Beamforming
Math
Is
Awesome.
One thing I wonder is, what if it was once there, but is no longer? Stars form in tight clusters, and planets in extremely wide obits like that are the most easily disrupted by close stellar encounters. Things that far out aren't held on to that tightly. Let's say Planet IX did exist at the beginning of the Solar System, influenced the orbits of all these Kuiper Belt objects, but then was later ripped away by another star passing close to the Sun ("close" on interstellar distances.) Would the patterns we observe in the orbits of KBOs still remain, or would they drift with time? Recent surveys suggest that something like half or more of planets are interstellar, not bound to any star. Most of these rogue planets likely formed around stars and were later torn from their orbits by close stellar encounters. It's not impossible that Planet IX did exist, set up the orbits of the KBOs, and was later torn away by a passing star when it was way out at its Aphelion. But I wonder if the effects we observe in the KBO populations would still remain, even if the planet that formed those patterns was torn away several billion years ago.
First, the Solar System is only a few billion years old, not several (not a huge distinction, but it can be meaningful depending on your definition of "several").
More importantly, though, over billions of years, the effects of the planet would be erased by the gravity of other planets, not to mention the likelihood that a star coming through and ejecting Planet 9 would likely fuck up the orbits of the planetoids out there. The orbits are (hypothesized to be) caused by harmonic resonances with the orbit of Planet 9 and outer-Solar System planets, so if you get rid of the Planet, you get rid of the resonances keeping them in place.
This is the process for finding the damn thing. IIRC, Neptune and Pluto where theorized to exist before we actually observed them. It's through these methods that we can hope to find such a dark, far planet.
One of the authors of the paper walks everyone through it and answers a lot of questions about it in this episode of Event Horizon. This is conclusive. There is something larger than any of the inner planets out there and that question is now settled with hard evidence, period. The what and where are the more interesting part, and now we can start looking for it instead of entertaining arguments about if it exists in the first place. It will be an awful lot more easy to get telescope time for this hunt going forward.
They may name it "David Bowie" if for no other reason than all Greek names are already spoken for with other celestial objects.
That's a great video! Thank you!!
It's definitely a large alien ship with a cloaking device, inhabited by owl people with antlers.
It’s a consequence of demoting Pluto, that our Solar System has to have nine planets, so a new one will come out from the aether and somehow the science will justify it. The Pizzas must be served!
mild spoilers for the video game referenced
Inhabited by *the disembodied souls* of owl people with antlers. The Stranger was almost totally devoid of life, remember?No, pretty sure it's a macroscopic quantum object of some kind that's older than the universe itself.
Don't be a rube, it's lizard people.
Obviously a large teapot.