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Mike Brown recently wrote a summary of his and Konstantin Batygin's paper 'The orbit of Planet Nine'. By looking at Kuiper belt objects (KBOs) whose orbits appear skewed by the invisible gravity of a possible Planet Nine, accounting for observation bias, and running a ton of simulations and MCMC, they concluded: if it exists, Planet Nine has a mass of 6.2 (+2.2/-1.3) Earth masses and a perihelion (closest approach to the Sun) of 300 (+85/-60) AU. The median distance at aphelion is around 500 AU. Those are not small error bars, but they do constrain the search, and this proposed finding of 225±15 AU and a mass of 3-5 ME could just ~barely~ fit.

The summary: https://findplanetnine.blogspot.com/2021/08/the-orbit-of-pla...

We’ve been covering this search in Orbital Index (https://orbitalindex.com), subscribe if you want updates.

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According to Mike Brown, the infrared sighting from Rowan-Robinson is in a different location in the sky than was predicted by the aforementioned Planet Nine hypothesis.

In other words, if this infrared sighting is real it would be a different Planet Nine!

https://twitter.com/plutokiller/status/1458038427090178052

Planet 9 3/4?

Isn’t that where you board Galaxy Express 999?

Harry Potter and the Conspirator's Planet.

So if it turns out that both this object and the hypothesized Planet 9 exist, which one is further out and gets to be Planet X?

I really like how that worked out that X would be 10 instead of placeholder_name, and I do hope that at least our grandchildren will see such a discovery.

I’m just mad we’re losing out on “Planet X”. When I was a kid Pluto was a planet so the new one was X (10) and it was cool. Now this new planet is just going to be planet 9 again… totally lame.

Oh man this was me! I 100% agreed until I saw relative size of Pluto[0].

Definitely seems unfair to call it a planet when there's a number of Kuiper belt objects that are larger[1](?) or pretty much the same size.

[0] https://www.quora.com/Why-is-Pluto-so-different-from-the-oth...

[1] https://www.universetoday.com/118118/it-looks-like-these-are...

Planetary scientists tend to consider Pluto, and those large Kuiper Belt Objects, to be “planets.” It’s just certain astronomers, who don’t usually study planets, who voted to remove them from planethood. https://www.ucf.edu/news/pluto-planet-research/?amp

Pluto is an impressive planetary system with a bunch of Moons and active geology. I’m gonna call it a planet.

Also kind of funny, but this guy who is obsessed with finding “Planet 9” (which doesn’t seem to exist) is also the one who tried and succeeded at demoting Pluto.

Can't we just add Pluto and Charon together and say "by your ~powers~ masses combined, I am ~Captain~ the ninth Planet!"

Pluto is closer in size to Earth than Earth is to Jupiter, but we lump them both into the same category.

There was a real concern that we were going to find thousands of Pluto sized objects in the kuiper belt, and that when we observed them up close they were just going to look like big comets. Instead it turns out there are only a handful and they are fascinating worlds with many similarities to other planets.

But it's from outer space.

The .plan thread is four up from here.

I think Planet IX has a better ring to it.

But I also enjoyed reading the Dune series by Frank Herbert.

Many machines on IX.

Better than those on Richese.

Uncle Malky deserved better.

Maybe there's a second one!

Planet 9 II

Perhaps a dumb question, but if we have some idea of where it was and its probable orbit back then, then why don’t we have some idea of where it is now?

Not at all a dumb question! The argument goes that we haven't had powerful-enough telescopes (or enough dedicated observing time) to image it.

Not everyone buys this; some people think it does not exist, and the perturbed orbits of Kuiper Belt objects are just a random fluke.

"Some idea" is the problem. Basically at the orbit we think it's at, even at the relatively large size they're expecting, it would be a tiny, tiny black dot. It's the proverbial needle in a haystack, knowing which haystack it's in is only the beginning.

I wonder how far would it be from New Horizons.

The scientist that found this potential planet in the old data did calculate the location where the planet should be and provided it in his article.

I'm sure there will be follow up studies and some telescopes will be pointing.

Yes we should.

Also, Mike Brown's free 'The Science of the Solar System' course on Coursera is excellent. Highly recommended. https://www.coursera.org/learn/solar-system

Excellent suggestion!

Love the newsletter by the way. It's the only one out of dozens I receive that I actually read every time.

I can recommend anyone that has an interest in anything space related to give it a read.

Thank you! I’m glad you’re enjoying it.

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