[HN Gopher] Is Planet Nine Alone in the Outer System?
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       Is Planet Nine Alone in the Outer System?
        
       Author : JPLeRouzic
       Score  : 56 points
       Date   : 2025-05-06 17:29 UTC (5 hours ago)
        
 (HTM) web link (www.centauri-dreams.org)
 (TXT) w3m dump (www.centauri-dreams.org)
        
       | rdtsc wrote:
       | Previous discussion https://news.ycombinator.com/item?id=43874641
       | 
       | Link to the paper:https://arxiv.org/pdf/2504.17288
        
       | Qem wrote:
       | > Brown argues that this object is not likely to be Planet Nine
       | because its orbit would be far more tilted than what is predicted
       | for the undiscovered world. In other words, a planet in this
       | position would not have the observed effects on the Solar System.
       | In fact, a planet in this orbit would make the calculated Planet
       | Nine orbit itself unstable, which would eliminate Planet Nine
       | altogether. Is there an entirely different planet out there?
       | Future observations will have to sort this out.
       | 
       | There's also an alternative lesser known proposal for an
       | undetected massive object in the outer solar system, by Lykawka
       | and Mukai[1], ofter confounded with the planet nine hypothesis,
       | but it is actually an independent proposal from the object
       | predicted by Batygin and Brown. I wonder if despite not being
       | compatible with the more known planet nine proposal, the recent
       | finding may be compatible with the one from Lykawka et al, or it
       | may even be the case that the former acts in tandem with the
       | later, and we actually have two real objects making the work of
       | the virtual single planet proposed by B&B.
       | 
       | [1]
       | https://iopscience.iop.org/article/10.1088/0004-6256/135/4/1...
        
       | eth0up wrote:
       | I'm going with little black hole
        
         | schrectacular wrote:
         | I mean how else would the aliens have gotten here?
        
       | xhrpost wrote:
       | > The authors say that the 570 megapixel Dark Energy Camera
       | (DECam) may be useful for follow-up observations.
       | 
       | I was curious what kind of resolution you'd have at this distance
       | but not sure I did the math right. The camera has a resolution of
       | 0.27"/pixel[1] which is 0.000075 degrees. Then to get size at
       | 500AU -> tan((pi/180) * 0.000075) _(500_ 149597870700)
       | ~98megameters, which is like 8 earth diameters. Is this right?
       | 
       | [1]: https://www.darkenergysurvey.org/the-des-
       | project/instrument/...
        
         | georgeburdell wrote:
         | Sub pixel resolution is possible by observing the space over
         | time
        
       | adrian_b wrote:
       | The fact that many trans-Neptunian bodies have weird orbits is
       | not a correct argument for the existence of an extra big planet
       | beyond them in the present time.
       | 
       | It is only evidence that at some moment in the past there was
       | something big out there, which has perturbed their orbits.
       | 
       | In 2024 there have been published a few papers which propose that
       | a star has passed close to the Solar System in the past and its
       | passage has caused all the unusual orbits that we see in the
       | outer Solar System.
       | 
       | This seems more plausible than an undiscovered big planet.
       | 
       | https://www.nature.com/articles/s41550-024-02349-x
       | 
       | https://iopscience.iop.org/article/10.3847/2041-8213/ad63a6
        
         | Qem wrote:
         | > This seems more plausible than an undiscovered big planet.
         | 
         | Both are plausible, both are intriguing. To determine what in
         | fact happened there's no way around looking up and searching
         | until we exhaust the possibilities. Kudos for Terry Phan and
         | his team for putting in the work, regardless of what hypothesis
         | it ends strenghtening.
        
           | adrian_b wrote:
           | Evidence for a currently existing outer planet would be
           | provided only when we would see _changes_ in the orbits of
           | the known bodies.
           | 
           | Unusual values of the orbital parameters are only evidence
           | for something that has happened in the past.
        
         | charlieyu1 wrote:
         | From the first link:
         | 
         | > The Solar System planets accumulated from a disk of dust and
         | gas that once orbited the Sun. Therefore, the planets move
         | close to their common plane on near-circular orbits. About
         | 3,000 small objects have been observed to orbit the Sun beyond
         | Neptune (rp > 35 au); surprisingly, most move on eccentric and
         | inclined orbits. Therefore, some force must have lifted these
         | trans-Neptunian objects (TNOs) from the disk where they formed
         | and altered their orbits markedly.
         | 
         | I feel there is a strong bias towards objects that are only
         | discoverable because of their highly eccentric orbit
        
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