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Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

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Re: Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

#71

Post by geuis »

swayvil wrote: post #48
tliltocatl wrote: post #35

Earlier quoted context omitted.

The rest of the planets are theorized to have condensed from the protoplanetary disk that formed the same molecular cloud the Sun did. I. e. they have formed at approximately same time as the sun and from same material, sans gravitational separation.

Ah, so a captured body would be quite different and alien. Really old too. Like, first generation of stars.

Would likely be older than the solar system itself. Probably not first gen star old, but likely would have formed before the sun did. Don't know how different it would be though. Would have formed out of maybe different ratios of elements than what was in the molecular cloud we formed from, but otherwise a large body like this would have undergone similar geological processes as our own planets.

Re: Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

#72

Post by perihelions »

DiogenesKynikos wrote: post #66
bikenaga wrote: post #2

Original paper: https://arxiv.org/pdf/2504.17288

They forgot to change the title from "Overleaf Example" in their LaTeX source file.

It's "hello, world!" planetary science with "hello, world!" tooling!

Re: Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

#73

Post by dotancohen »

s1artibartfast wrote: post #62
tliltocatl wrote: post #58

Earlier quoted context omitted.

Not true. An obit is not an infinite "plain" with a finite "hill" on but rather a finite "valley". The ball will exit the valley on the other side unless it loses excess kinetic energy somewhere in the valley.

Correct, but my point is you don't need to lose energy to enter orbit. You don't need complex reverse slingshot interactions. You just need a low enough relative velocity to not shoot off the other side. I would expect this to be the norm for capture, not some exotic phenomenon. A ball doesn't need to lose energy to be captured in a valley either. You just apply a radial force to turn a line into a circle. Anything t…

To all other readers: this is wrong.

Re: Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

#74

Post by water-data-dude »

1970-01-01 wrote: post #30
AIPedant wrote: post #11

I think “15 times further from the Sun than Pluto” is more meaningful for most readers than “700 times further from the Sun than Earth.” If it exists, it’s way way way out there.

Yes, also being 10x the mass of Earth that far out hints that it may be an interstellar object captured by the Sun.

I wanted to get a sense of what that MEANS relative to the rest of the gas giants. Apparently it’d be roughly the size of Uranus or Neptune.

I guess I’d always put all the gas giants in the same “very, unimaginably big” bucket. I knew Jupiter was the biggest, then Saturn, but I didn’t realize just HOW big they were compared to the rest. At the risk of stating the very, very obvious, Jupiter is huge!!!

Masses of gas giants are: Jupiter, 317.8 earth mass; Saturn, 95.2 earth mass; Neptune, 17.1 earth mass; Uranus, 14.5 earth mass

[0] https://en.m.wikipedia.org/wiki/Earth_mass#Unit_of_mass_in_a...

Re: Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

#75

Post by ars »

s1artibartfast wrote: post #62
tliltocatl wrote: post #58

Earlier quoted context omitted.

Not true. An obit is not an infinite "plain" with a finite "hill" on but rather a finite "valley". The ball will exit the valley on the other side unless it loses excess kinetic energy somewhere in the valley.

Correct, but my point is you don't need to lose energy to enter orbit. You don't need complex reverse slingshot interactions. You just need a low enough relative velocity to not shoot off the other side. I would expect this to be the norm for capture, not some exotic phenomenon. A ball doesn't need to lose energy to be captured in a valley either. You just apply a radial force to turn a line into a circle. Anything t…

That is not true. If it approaches with less than escape velocity it will gain all the velocity necessary to escape in the process of approaching the Sun.

You could think of it as speeding up as it falls toward the sun, it then slows down by the exact same amount as it leaves the Sun.

In order to stay near the sun it needs to lose some of that speed, and given that momentum is conserved, the only possible way is to either hit the Sun or send that momentum to a third object.

Re: Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

#76

Post by tlogan »

Projectiboga wrote: post #63
randomtoast wrote: post #6

I find one theory regarding Planet 9 especially interesting, and that is that it could be a primordial black hole with a Schwarzschild radius on the order of just a few centimeters. So basically, just a golf ball-sized black hole. This would explain why we can see the gravitational effects on the other objects as described in many papers, and it would also explain at the same time why we have no direct observation of…

If it were earth mass it would be ~grapefruit size. This estimate puts object nine at 9 earth mass so maybe vollyball size or melon size? https://www.astronomy.com/science/is-planet-nine-a-black-hol...

If I’m remembering right, compressing all of Earth’s mass would give a Schwarzschild radius of roughly 9 mm. I think Uranus (15x heavier than earth) would be like basketball.

Is my calculation correct?

Re: Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

#77

Post by tliltocatl »

s1artibartfast wrote: post #62
tliltocatl wrote: post #58

Earlier quoted context omitted.

Not true. An obit is not an infinite "plain" with a finite "hill" on but rather a finite "valley". The ball will exit the valley on the other side unless it loses excess kinetic energy somewhere in the valley.

Correct, but my point is you don't need to lose energy to enter orbit. You don't need complex reverse slingshot interactions. You just need a low enough relative velocity to not shoot off the other side. I would expect this to be the norm for capture, not some exotic phenomenon. A ball doesn't need to lose energy to be captured in a valley either. You just apply a radial force to turn a line into a circle. Anything t…

Anything that approaches the sun will do so with faster than escape velocity because the gravitational potential energy gets converted into kinetic during the approach. Newtonian mechanics is time-reversible - just like it's impossible for an object in orbit to spontaneously escape without gaining energy from somewhere first, it's impossible to enter orbit without losing energy to another body.

Re: Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

#78

Post by rozab »

perihelions wrote: post #15

This cannot be evidence of Planet 9 (the Batygin and Brown hypothesis)—it's outright incompatible with it. https://bsky.app/profile/plutokiller.com/post/3lnqm2ymbd22r If those two spots are the same object, that object is on a high-inclination orbit; but the pattern the Planet 9 hypothesis explains is only compatible with a low-inclination object.

Isn't this exactly how Pluto was discovered? Due to an innacurate estimate of the mass of Neptune (not corrected until Voyager I think), people were hunting for a large planet to explain the discrepancy. After a bunch of searching they happened to find Pluto, but it was not the Planet X they were looking for. The mass estimates for Pluto were gradually downgraded from many Earth masses to 1/500, which is the true reason it was initially classified as a planet.

Re: Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

#79

Post by magicalist »

margalabargala wrote: post #65
zveyaeyv3sfye wrote: post #61

Earlier quoted context omitted.

Not sure I want a black hole in my backyard ;-) For all it's worth, there's no need to go black hole to explain the lack of visual observation. Objects that far from a star reflect very little if any light and would appear black to a black background.

Black holes are no more "dangerous" than other objects of equal mass. If a black hole with a mass of, say, Ceres hit the Earth, it would not be particularly worse than if Ceres hit the Earth.

> If a black hole with a mass of, say, Ceres hit the Earth, it would not be particularly worse than if Ceres hit the Earth.

This equivalency is true for many aspects of orbital mechanics (depending on setup giving sufficient distance), but I don't believe that's true at all for a collision. Someone with more knowledge correct me, but a black hole with the mass of Ceres would be very tiny but also emitting a ton of radiation. The collision would be very different.

Re: Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

#80

Post by Nevermark »

ck2 wrote: post #25
AIPedant wrote: post #11

I think “15 times further from the Sun than Pluto” is more meaningful for most readers than “700 times further from the Sun than Earth.” If it exists, it’s way way way out there.

There's an episode on "Space & Beyond" where they show all the planets in scale to the realworld on an actual football field. Then to show Planet 9 distance they have to get in a car and drive a few miles. That worked for me.

I have a set of twelve books by an artist, titled "Astronomical" (one book for each letter). The first page shows the sun, then the rest of the books are almost all simply black pages, but with the planets and asteroid belt entities shown with accurate distance and size scale.

It communicates the scales really well, while only taking up a little over a foot of bookshelf space when not being "navigated". I have two heavy metallic retro looking rocket bookends for it.

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