Life is But a Stream: Planetary Systems Along Stellar Streams

Aside from potentially disrupting the planet forming disk, what else would be different about the life of a planet in one of these cluster environments?

Right.

So the main thing is you have other stars going by.

know where our sun right now is relatively alone but i mean inside a star cluster it's very different

um

so if you think of it kind of right now in the solar neighborhood where our sun is our nearest neighbor is something like four light years away ish which is like 10 trillion kilometers it's real far away so you can put a big you know you can imagine a sphere an imaginary sphere around our sun uh with a radius of four light years and there's really only one star there us But in a star cluster, there can be hundreds or tens of thousands of stars in that same volume, which means you're going to have relatively close interactions.

And so sometimes that can result in a gravitational perturbation that could knock a planet off its original orbit that it formed on to something maybe more eccentric or more inclined, or it could even strip a planet entirely.

And then that can cascade as you have planet-planet gravitational interaction, so you can really kind of stir up or mix planetary systems or mix up planetary systems, thanks to these external perturbations.

And that's just gravity, right? You also have massive stars that might be undergoing supernovae events.

You can have binaries.

You can get stars kicked kind of violently from the cluster center.

So there's a lot going on that can not be great for a planetary system, depending on where it is.

And then.

What makes it hard, though, to study exoplanets in these systems is the same reason they're so interesting.

They're so dense.

And so it's hard to kind of pick one star and try to whether you're looking at its light curve and how much light planets might block from the host star or whether you're looking for like changes in its motion due to the presence of planets.

That's hard to do because there's so many other stars around.

Mm hmm.

But if you wait till that star cluster breaks up and you look at it as a stellar stream, all of a sudden it's kind of been unpacked and you have all these stars that are in a lower density environment that's much easier to study, but they will have spent a long time in a star cluster before that.

Very true.

And so it's pretty hard to observe these, maybe not quite as hard, though not simple, to simulate them.

Yeah,

yeah.

I mean, that's one of the fun parts of being the theory side of things is that you can simulate these things and look at them for billions of years of evolution and you can see exactly what they look like at closer scales.

But of course, you're guessing at how well they represent reality.