Previous discussion https://news.ycombinator.com/item?id=43874641

Link to the paper:https://arxiv.org/pdf/2504.17288

> 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...

I'm going with little black hole

> 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/...

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