JuMBO conundrum - planet, not planets

[Pupp]

https://www.theguardian.com/science/2023/oct/02/ju...

Always knew that Orion fella was a bit suss; hanging around with his gaudy belt and big sword…

[Eric Mc]

Not a surprise really as it has been recognised for quite a while that there will be some planets floating freely between the stars i.e. not in an orbit around a parent star. Objects get ejected from their own solar systems sometimes.

[budgie smuggler]

Eric Mc said:

Not a surprise really as it has been recognised for quite a while that there will be some planets floating freely between the stars i.e. not in an orbit around a parent star. Objects get ejected from their own solar systems sometimes.

It is a surprise that they are binary objects. As Mark McCaughrean explains:

"Gas physics suggests you shouldn't be able to make objects with the mass of Jupiter on their own, and we know single planets can get kicked out from star systems. But how do you kick out pairs of these things together? Right now, we don't have an answer. It's one for the theoreticians,"

[deckster]

Eric Mc said:

Not a surprise really as it has been recognised for quite a while that there will be some planets floating freely between the stars i.e. not in an orbit around a parent star. Objects get ejected from their own solar systems sometimes.

Yes, but also no. From the article:

Guardian said:

We find them down as small as one Jupiter mass, even half a Jupiter mass, floating freely, not attached to a star,” he said. “Physics says you can’t even make objects that small.
<....>
The latest observations are more challenging to explain because, out of the hundreds of roughly Jupiter-sized objects found, dozens are in binary pairs. “How can you throw two things out [of a star’s orbit] in a chaotic interaction and get them to stick back together again?”

So no surprise that there are inter-stellar objects. But they are too small and being found in pairs. Which is exciting because it means that some of our explanations of solar and planet formation are wrong. And as we know, there is nothing a scientist likes more than finding out that somebody else is wrong

[Eric Mc]

I don't think size matters as to whether an object gets flung out of its solar system. However, having a pair of objects ejected together is a bit strange - although it does indicate that some planets might form in a young solar system quite close to each other. That would make sense if the dust and gas material from which these particular planets formed was a bit lumpy (highly likely) allowing two objects to coalesce far enough away to form separately but still gravitationally connected. Therefore, if one gets ejected, its companion gets ejected too.

All very interesting.

[bmwmike]

Why are they presumed to have been flung out? Are they not gas giants, could they not have formed in that area and naturally attracted to each other and eventually coalesce into one larger object?

[deckster]

bmwmike said:

Why are they presumed to have been flung out? Are they not gas giants, could they not have formed in that area and naturally attracted to each other and eventually coalesce into one larger object?

That is the problem. According to current theories of planetary formation, the minimum size for an independent planet to form is 6-7 Jupiter masses and these are much smaller than that. So the accepted explanation is that they would had to have formed inside of a solar system and then been ejected.

However the observation is that these are binary planets that are gravitationally bound. And current theories of planetary ejection wouldn't allow for this - and certainly not at the level that has been observed.

So one (or perhaps many) of our theories is wrong, somewhere. Which is exciting!

[bmwmike]

Thanks Deckster, I see the issue now.

[Eric Mc]

I think we will find that all sorts of objects coalesce out of dust clouds, some as part of rotating discs (which form typical solar systems with planets orbiting a star) or perhaps isolated planet type bodies that form independently - or perhaps in small groups of two or more.

[Mr Whippy]

Exactly.

Model doesn’t fit new data shocker.

JWST was worth the effort I’d say!