by Chris Peterson » Thu Mar 07, 2019 7:35 pm
geoffrey.landis wrote: ↑Thu Mar 07, 2019 7:05 pm
Chris Peterson wrote: ↑Wed Mar 06, 2019 5:21 pm
... There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.)
Dark matter accumulates inside a gravity well (since it has mass), and the amount by which it is concentrated in the gravity well depends on the mass and temperature (according to the law of Jeans' escape). So, yes, dark matter would be somewhat concentrated inside the sun. Different models predict different temperatures-- cold dark matter, warm dark matter, and hot dark matter are all models still in contention.
However, the density of dark matter is so low, and its interaction with ordinary matter so extraordinarily low, it's unlikely to have any significant effect (it only plays a role in galactic rotation because even a very low density of matter adds up over volumes of space measured in trillions of cubic parsecs).
In the absence of interaction with other matter, it is unclear why dark matter would concentrate in an gravity well. It might
orbit around a gravity well, but would not necessarily concentrate. To do that, it would required some mechanism for transferring momentum. With ordinary matter that's mostly via electromagnetic interactions. Of course, we don't know how dark matter interacts with itself (other than straightforward gravitational interaction), so that's a big unknown in terms of hydrodynamic equivalents in dark matter.
[quote=geoffrey.landis post_id=290437 time=1551985505 user_id=128095]
[quote="Chris Peterson" post_id=290411 time=1551892913 user_id=117706]
... There is no evidence that dark matter is concentrated in the Solar System, or in the Sun or planets. (No evidence doesn't mean it isn't, just that for now, there's no reason to believe it is present, and we have no observations that would be better explained by positing a dark matter involvement.)
[/quote]
Dark matter accumulates inside a gravity well (since it has mass), and the amount by which it is concentrated in the gravity well depends on the mass and temperature (according to the law of Jeans' escape). So, yes, dark matter would be somewhat concentrated inside the sun. Different models predict different temperatures-- cold dark matter, warm dark matter, and hot dark matter are all models still in contention.
However, the density of dark matter is so low, and its interaction with ordinary matter so extraordinarily low, it's unlikely to have any significant effect (it only plays a role in galactic rotation because even a very low density of matter adds up over volumes of space measured in trillions of cubic parsecs).
[/quote]
In the absence of interaction with other matter, it is unclear why dark matter would concentrate in an gravity well. It might [i]orbit [/i]around a gravity well, but would not necessarily concentrate. To do that, it would required some mechanism for transferring momentum. With ordinary matter that's mostly via electromagnetic interactions. Of course, we don't know how dark matter interacts with itself (other than straightforward gravitational interaction), so that's a big unknown in terms of hydrodynamic equivalents in dark matter.