Question

Please help...astronomy is killing me...Why can't dark matter cool down? and what consequence does that have for the size of a dark matter halo?

Answer 1

i'm never sure what's astrophysics, astronomy, or cosmology. I'd wonder whether "dark matter" (the matter that physicists reckon is needed - but unseen for some reason - to balance their equations for the total mass in the universe ?) was astrop or cosmo. Or maybe that's me being picky ?

Answer 2

i think its part of all of those but there are different parts of it to study

Answer 3

im studying the astronomy side of it

Answer 4

do you know anything about it ?

Answer 5

the universe is made up of about 25% of dark matter. as the consequences of Einstein general theory off relativity the universe is expending due to the cosmological constant .
Much of the evidence comes from the motions of galaxies.Many of these appear to be fairly uniform, so by the virial theorem, the total kinetic energy should be half the galaxies' total gravitational binding energy. Observationally, the total kinetic energy is much greater. In particular, assuming the gravitational mass is due to only visible matter, stars far from the center of galaxies have much higher velocities than predicted by the virial theorem. Galactic rotation curves, which illustrate the velocity of rotation versus the distance from the galactic center, show the "excess" velocity. Dark matter is the most straightforward way of accounting for this discrepancy.
"Cold" dark matter offers the simplest explanation for most cosmological observations. It is dark matter composed of constituents with an FSL much smaller than a protogalaxy. This is the focus for dark matter research, as hot dark matter does not seem to be capable of supporting galaxy or galaxy cluster formation, and most particle candidates slowed early.

Answer 6

@vipulrakta
virial theorem
is this the same "virial" as in thermodynamics ???
you write like a cosmologist ?
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