Astronomer Mike Brown said he thought "Planet 9" would be found by the Spring of 2018, so that prediction has one more month of shelf life. I am of the opinion that Mike Brown will be proven wrong here, i.e., Planet 9 does not exist.

"A star is expected to pass through the Oort Cloud every 100,000 years or so. An approach as close or closer than 52,000 AU (Scholz's Star) is expected to occur about every 9 million years."

https://en.wikipe...z's_Star

That means Mike Brown's simulation failed to account for any one of the approximately 45 thousand close encounters since the solar system was formed. This is a gigantic, gaping hole in Mike Brown's simulation. This also ignores the arguably far more interesting story of exchange of materials during these close encounters like asteroid 2015 BZ509, which is apparently of interstellar origin.

https://phys.org/...lar.html

disruptions of the Oort Cloud by stellar encounters are simply not mutually exclusive with a massive planet doing the same to the same family of objects or others.

That makes obvious sense to you and me, at least at the start of the analysis when one cannot readily distinguish between the effects of a close stellar pass and a Planet 9. However, Batygin & Brown concluded the only remaining possibility was Planet 9.

Unless you want to argue all the searches for Planet 9 since the Batygin & Brown announcement have been completely useless, the chances of Planet 9 hiding out there in some unsearched corner grow increasingly slim with time.

Another possibility is that Planet 9 existed at one point in time, but was later removed by a close stellar pass or series of close stellar passes. This is yet another scenario Batygin & Brown did not consider at all when they concluded that Planet 9 currently exists in the outer solar system as they specified.

Scolar_Visari, here is my predicted answer, which has not changed since no later than April, 2016:

There is no Planet 9 because the outer solar system is far more dynamic over geological time scales than we had previously thought. The simulation of Batygin & Brown is fundamentally flawing for ignoring this fact. Eventually Batygin & Brown will conclude the same thing.

https://phys.org/...net.html

There's a slight difference between a single stellar pass, and a body in orbit that consistently perturbs. Additionally, ~45k close encounters would mean that one would expect ~45k different configurations of perturbed orbits (I'm assuming that orbits this distant are stable enough not to change much, but here almost all of them seem to be perturbed in the same way.

The closest and most recent stellar passes might have the most noticeable effects on current Kuiper Belt, Scattered Disk and Oort Cloud orbits. Close passes by other stellar objects are potentially messy encounters with extended portions of a passing solar system and ours potentially coming into relatively close contact. Unlike some papers that described these outer portions of our solar system as containing "pristine" objects, the amount of chaos and mixing by tens of thousands of close passes must be profound. For example, I would expect to find objects with a great diversity of origins that formed under a great diversity of conditions, including much higher temperatures than typical for their areas of space. Add this to the mountain of reasons to keep exploring the solar system.

I think Planet Nine has already been found in 2002 - 2004. Astronomer Forbes almost found in 1880. Madam Blavatsky sensed it around 1900 and told us how to find it and called it 'Vulcan'. You can find its mass and orbital parameters here:

http://barry.warm...led.html
VULCAN REVEALED
A Dangerous New Jovian Sized Body In Our Solar System

Scolar_Visari, a number of professional astronomers have questioned Batygin & Brown's conclusions. Considering B&B have argued since 2016 that Planet 9 exists, but nothing has been found, I would say the burden of proof is on them more than ever to make their case. To my knowledge, B&B have not proven their case is better than the close stellar passes case and the single paragraph in section 4.2.1 of the paper here is not exactly a tour-de-force on this subject.

I would also note that the simulation in the paper is with Planet 9 at a very convenient 700 AU, but that area of space has arguably already been ruled out by existing surveys. I find it hard to believe a 10 Earth mass planet is lurking unseen a mere 700 AU away, resisting all attempts to locate it, including NASA's WISE mission.

"Right now, any good scientist is going to be skeptical, because it's a pretty big claim." – Mike Brown

https://www.pbs.o...presence

I read Astronomer David Jewitt and others had questioned the existence of Planet 9. If I get a chance I will look for some of the articles I read before.

In any case, you have ignored:

1. Mike Brown's prediction that it would be found by the Spring of 2018 is about to fail.
2. Nothing has been found, even though many have looked, limiting the area where Planet 9 could be found.
3. The 700 AU figure came from the paper, not me.
4. Nobody has done a great job simulating the effects of all those close stellar passes probably because it is a tremendously difficult task due to the chaotic nature of all the close encounters.

A agree that the odds are what is happening out there is not a coincidence, but that does not make B&B right.

I give it about a 1% chance of turning out to be real," says astronomer JJ Kavelaars, of the Dominion Astrophysical Observatory in Victoria, Canada.

http://www.scienc...net-nine

Indeed, Paul Delaney, an astronomer at York University, notes that the effects attributed to Planet Nine could be explained by other phenomena or by simple chance — however remote.

https://www.thest...uto.html

@Scolar_Visari.

I can't help wondering: Given the voluminous past and present stellar observations data, and especially the more recent 'planet hunting' efforts (using dedicated planet-hunting scopes/instruments capable of detecting the very small stellar radiation 'drop' when planets pass across our line-of-sight to the host stars), shouldn't we have detected by now Planet Nine (in our own outer solar system) passing across our line-of-sight to whichever distant stars it would be 'eclipsing' totally?

ie, IF the (postulated) Planet Nine moved along its orbital arc so far observed, there should be a detectable 'serial eclipsing' of a 'line' of stars normally visible along that arc-line in the sky.

Have you (or anyone else) seen any papers/comments anywhere in the literature considering/pursuing this particular line of enquiry/observation/logic? If so, I would be much obliged for any link(s) to same.

Thanks, SV. :)

what this forum needs is Oliver Manuel, Ph. D.

These papers directly or indirectly conclude passing stars can affect the orbits of outer solar system objects and make them less circular and/or move them out of the plane of the solar system.

"We ran a grid of simulations for a flyby star . . . The effect on the disc is slight but clear starting at 40 AU, where particles reach an eccentricity up to 0.1"
https://arxiv.org...2412.pdf

https://arxiv.org...2644.pdf
https://arxiv.org...02.00778
https://arxiv.org...01.10254
https://arxiv.org...02.04655
https://www.acade.../7212353

1. So what if Brown's Magic 8-Ball level prediction is wrong?
Obviously this increases the desirability for a new hypothesis to explain the strange orbits of the bodies B&B were looking at.

2. Having not found Planet Nine hasn't really had anything to do with the other claims you've made regarding its general validity.
Wrong, the more we look and don't find, the more likely B&B's simulation is a either wrong or a red herring .

3. From what paper?
See some of them above.

4. That stellar encounters haven't been modeled in detail isn't that big a problem in this particular case given that we already have a good fit for an unseen planet in the data.
You can't simply conclude that makes it right, especially when the evidence is going the other way.

No one is saying Brown et al. are correct
- Good, because I am saying there is a good chance they are incorrect.

@Mark one of the points @Visari is making is that multiple encounters with extra-Solar System objects are required to give the results, which can be explained by only one large planet. The former are much less likely than the latter. This is a form of Ockham's Razor. If we're betting money I'm going with the Razor.

multiple encounters with extra-Solar System objects are required to give the results

I have read this before, but I have not seen convincing evidence this is true. If a star were to pass by or through our solar system it's gravity would change the orbits of the closest bodies in the solar system, as mentioned in a number of the papers I cited. A single stellar encounter would be enough to permanently change these orbits.

If Planet 9 does not exist, we need to consider other alternatives. It is possible that stellar encounters may not be source of effects B&B identified, but if a star has passed through the Oort Cloud every 100,000 years they are certain to have a significant effect at least in the Oort Cloud.

granville, a planet is a sub-stellar, celestial body at least 2,000 kilometers in diameter. Or at least by my personal definition it is. By that definition, we have ten known planets in the solar system including Pluto and Eris.

Although it is not perfect, I would put my personal planet definition up against the IAU's any day of the week. Orbiting the sun, or anything else for that matter, is not required, neither is "clearing the neighborhood."

granville, if you would like, consider my definition, I think it works pretty well.

"A planet is a sub-stellar, celestial body at least 2,000 kilometers in diameter."

I feel like this definition cuts the proverbial Gordian Knot. The difficulty of precisely defining the high end of the range is set aside for now by selecting "sub-stellar." "Celestial body," similarly eliminates other natural and artificial objects. Because the vast multitude of objects out there must constitute a continuum, an arbitrary, but precise number is probably the best choice. The 2,000 km limit is nice round number easy to use and remember, although we may have to consider it an average. There is a nice gap in objects in our solar system between Makemake and Eris, so nothing is close to the cutoff. Having ten planets is also a nice round number. More subtly, this definition encourages us to send a probe to Eris as the last remaining unexplored planet in the solar system.

I also like how exoplanets and rogue planets are now simply planets too. So an object that is an "Earth twin" would still be a planet regardless whether it orbited another star or no star at all.

One remaining problem is how to deal with the question of where to draw the line between a large moon and a double or multiple planet. I haven't figured that one out.

At the high end, science may eventually give us a better answer, such as less than 13 Jupiter masses, etc.

Maybe someday we will know so much about so many planets that we will be able to select a better number for where planetary processes begin, but for the moment, a 2,000 kilometer diameter is probably very reasonable given what we know.

BTW, this definition would also correct the mistake Mike Brown made in taking pride in killing Pluto's status as a planet and give him the credit he deserves for discovering our tenth planet, Eris. This will also give Mike Brown some solace for when his predicted "Planet 9" fails to materialize.

granville, a planet is a sub-stellar, celestial body at least 2,000 kilometers in diameter. Or at least by my personal definition it is. By that definition, we have ten known planets in the solar system including Pluto and Eris.

Although it is not perfect, I would put my personal planet definition up against the IAU's any day of the week.

Yeah. It *was* the IAU's definition--their proposed one, anyway--until a few hundred of them hijacked the system and manipulated the situation to force through the flawed definition we have today. There are geophysical planets that are smaller, like Ceres and Makemake, but at 2000 kilometers diameter a planet is massive enough to hold on to an atmosphere--for example, Pluto.

Lol, so nibiru exists after all

Not an astronomer, but have a question. Could the egos of certain posters be adversely affecting the planets orbits?

The first logical conclusion is that no celestial body from the other solar system can have a closed path (ellipse) around the other solar system. That is, if there are planets 9, it must belong to our solar system. But it is a big question: how can such a large planet be forced to circle around our sun at a distance of 700 AU? Secondly, how did those experts calculate or measure the size of the eccentricity, when they do not know the position of perihel and afel?
Thirdly, if such a planet exists, the perianth of the solar system would not lie in the sun itself, then the sun would have its rotation around the pericent at a distance greater than the radius of the sun. How would the sun behave?