Heliopause boundry

[neilsox]

Can someone explain why we think the heliopause is a distinct boundary? Very indistinct seems likely to me, because the photons and particles streaming out of our solar system would rarely interact significantly with those streaming out from other solar systems. Does the 500 kilometers per second of the solar wind near Earth's orbit slow to even 400 kilometers per second due to the gravity of our solar system? Neil

 

[MeteorWayne]

Hi Neil, the reason is that the gas and dust outside of our solar system is on it's own orbit around the galaxy which is not the same as that of the solar system. So there is always a speed difference between material (in this case the solar wind) bound to a star, and the material outside of that transition. We have evidence of strong interactions occurring there from various spacecraft, and of course the Voyagers are passing through this zone now. As always, our understanding will increase as we gather more data.

MW