Dark matter rival boosted by dwarf ga...

Dark matter rival boosted by dwarf galaxies

There are 1 comment on the New Scientist story from Mar 1, 2013, titled Dark matter rival boosted by dwarf galaxies. In it, New Scientist reports that:

Dwarf galaxies dancing around the spiral galaxy Andromeda have boosted a controversial alternative to the idea of dark matter - the invisible stuff that most astronomers think makes up about 80 per cent of the matter in the universe.

Join the discussion below, or Read more at New Scientist.

“Geologist [I'm Climate Change]”

Since: Mar 07

formerly Nuneaton

#1 Mar 4, 2013
Definitely like the idea of MOND. The fun bit here is that objects orbit the centre of mass. In a galaxy the centre of mass is the sum of all the masses in a galaxy. for stars near the core the bulk of the mass is on the outside of the star and the star should drift to the outside in a slow orbit (but the sum is in the centre). In stars close to the edge the sum of mass is in the core and practically all the mass is in the vicinity of the centre (orbital motion is fast). This is not the same as in the orbital dynamics of the heliocentric solar system!

The smoke fuzz orbital dynamics supercomputer calculations seem to come up closer to the mark than most of the math models so far, but a real run will come up with a loss of a fair chunk of outer stars from the initial blob and the generation of an elliptical bar in a halo.

It also appears that a lot of the cold dark matter the theory harps on about happens to reside in the form of small chunks.

Reality in large spirals & their dwarf halo is likely 6 of one and half a dozen of the other.

Giant galaxy clusters with an intracluster pool of hot gas have readily identifiable mass. It is not dark in that case but very hot and likely difficult to see without the right kit. The cold dark matter chunks are also likely to eventually be evaporated leaving only planet sized bits & stars & odd compact objects in the mix. The interesting thing in that case is mass lensing by big clusters, giant ellipticals in particular in the younger clusters which have not yet been stripped by collisions appear to leave hot gas contrails behind responsible for lensing of background objects well away for the galaxy core.

One other item of note here is the recent publication of a thin gas background in which galaxy groups (spirals typically such as the local group), are embedded and moving at a peculiar velocity. For galaxy groups peculiar velocities are up to 220Km/sec compared to neighbouring groups. Since the thin gas pool is likely unconnected to the galaxy groups moving through it, it is likely that this thin gas also has mass and is likely capable of ram stripping dwarf ellipticals but not dwarf irregulars or spirals which instead accrete the gas. This gas should also have mass and it should also affect the orbits of objects in it.

Have a nice day: Ag

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