Dark Matter Q

I dont know much about the research done on this dark matter... all I know
its elusive, there is indirect evidence of it, and its what holds galaxies
together... is it possible that this dark matter could be like a white dwarf
except completely cooled down so its one big chunk of 'metals'? This could
be why we cant see them as they are not glowing at all, they would be the
same temperature (or near enough) to space itself and thats why our infrared
telescopes haven't seen them... (or have we seen things that aren't hot or
bright?) however they would have to be substantially small, relatively, that
they wouldn't be detected when they pass our line of sight... I'm thinking
it would be fairly small stars with a short life span... just a thought...

Niko

"Niko Holm" wrote in
:

I dont know much about the research done on this dark matter... all I
know its elusive, there is indirect evidence of it, and its what holds
galaxies together... is it possible that this dark matter could be
like a white dwarf except completely cooled down so its one big chunk
of 'metals'? This could be why we cant see them as they are not
glowing at all, they would be the same temperature (or near enough) to
space itself and thats why our infrared telescopes haven't seen
them... (or have we seen things that aren't hot or bright?) however
they would have to be substantially small, relatively, that they
wouldn't be detected when they pass our line of sight... I'm thinking
it would be fairly small stars with a short life span... just a
thought...

You have identified one of the two leading candidates for dark matter.
Burned out small stars (ones too small to have gone nova) are called black
dwarves, and stars too small to ever have ignited are called brown dwarves.
Both of these objects, as well as other planetoids, planets and icy bodies
like comets, fall under the general category of MACHO's - Massively Compact
Halo Objects.

The other leading candidate is massive neutrinos, including both the muon
and tau varieties. These are called WIMP's - Weakly Interacting Massive
Particles.

There is experimental evidence to support meaningful contributions from
both of these categories. Brown dwarves were first observed a few years
ago, indirectly by means of the way they bent the light of nearby stars
when they passed near the line of sight between us and that star. And
experimental evidence for a neutrino mass was observed just this last year,
when the solar neutrino problem was solved, although there is currently
still no good estimate for the neutrino's mass.

But I hate the dumb names that physicists have given these two categories
of sources for the mass. These guys have gotta do better than that.

On Mon, 12 Jan 2004 09:01:19 +0800, "Niko Holm"
wrote:

I dont know much about the research done on this dark matter... all I know
its elusive, there is indirect evidence of it, and its what holds galaxies
together... is it possible that this dark matter could be like a white dwarf
except completely cooled down so its one big chunk of 'metals'? This could
be why we cant see them as they are not glowing at all, they would be the
same temperature (or near enough) to space itself and thats why our infrared
telescopes haven't seen them... (or have we seen things that aren't hot or
bright?) however they would have to be substantially small, relatively, that
they wouldn't be detected when they pass our line of sight... I'm thinking
it would be fairly small stars with a short life span... just a thought...

The proportion of Baryons (protons, neutrons, etc.) in the universe is
more or less known, so it's known that a substaintial portion of the
dark mass of the universe is not "normal" matter but some other
"non-interacting" particles. However a portion of dark matter is
normal, much of that is actually just so hot that it emits X-rays
rather than visible light.

--
Robb McLeod )
A bus station is where a bus stops. A train station is where a train stops.
On my desk I have a work station...

"Niko Holm" wrote in message ...
I dont know much about the research done on this dark matter... all I know
its elusive, there is indirect evidence of it, and its what holds galaxies
together... is it possible that this dark matter could be like a white dwarf
except completely cooled down so its one big chunk of 'metals'? This could
be why we cant see them as they are not glowing at all [...]

This is a reasonable question, and the main motivation behind OGLE and
similar projects. These stare at distant galaxies, watching for the
gravitational lensing that occurs when a large body (glowing or not)
comes close to the line of sight between us and one of the stars in
the distant galaxy. This effect depends only on gravity, and so could
detect the stars you mention. So far, their results show that at most
20% or so of the dark matter can be in the form of star sized bodies
(otherwise they would see more events than they do).
Lou Scheffer