eli5: Is the possible existence of a 9th planet actually back on the table now? If so, what did we find out?

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I’ve heard about this a few times recently, at first I chalked it up to the old, but viral “Planet X or Planet 9 discovered” hoax that’s been made on multiple occasions, but there’s a variety of recent articles pointing to the possibility. I am aware that such news brings a lot of trafic (so money) to news outlets, so I was wondering if this was simple sensationalist news or something we’re actually proposing again?

I definitely remember learning about how unlikely it was for a **real** planet beyond the orbit of Neptune to exist. (Fairly) Modern calculations and observations were also pointing towards it not even being a possibility.

So what changed in the last year? What have we learnt, observed, discovered, calculated, etc.? Is this misinformation or an actual old scientific hypothesis that’s being reinvestigated again in light of recent and new data?

(Possibly used the wrong flair, but it kinda made sense.)

In: Physics

8 Answers

Anonymous 0 Comments

A number of objects could be seen, and they implied there would be counterbalancing objects. So the call went out to look and instead other objects were found.

Basically, telescopes find what is in the light right now. That changes over time. Eons of time. So by looking hard, not so obvious stuff was found where the first call to look was.

The big kicker is infrared telescopes, including now available jwst, should be able to see any close planetary thing. The bigger the planet, the brighter it gets in infrared. So theres a cap on how big a thing could hide through this search.

Then recently, the growing list of new small objects have implied a new pattern.

So what the modern news really amounts to is that there’s a new hot patch of sky to look at. It’s probably light conditions have changed a little. Stuff out there moves very slow. No promises on what they find, but any informed clue helps narrow the sky. They haven’t been finding planets, but they are finding stuff.

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