What exactly is in the center of a galaxy? Its a big bright buldge, but is that just a high concentration of stars? If it is something else?

I think they don''t know exactly, but it might be lots of stars and/or black holes and/or dark matter. Make a Google search, you should get plenty of information.

Cédric

It''s a high-concentration of stars, which brings with it a high-concentration of other matter(okay, bring isn''t the right word), so it''s in one sense a vast nebula with hot-spots of fusion.

In the exact center, it''s been hypothesized that there is a large mass--a black hole size mass, that is to the stars like our sun is to the planets in our solar system.

quote:Original post by microdot
The latest research I''ve heard about supports the massive blackhole(s) in the center of the galaxy idea. I believe they measured the speed of some stars in the center and found that they were getting whip around at some insanely high speeds, which might support the whole super massive object in the center idea.

Observations on the center of certain galaxies have shown matter to be orbiting at >0.95c. The only currently accepted explanation (in that it is the simplest... mathematically and physically speaking) is that these galaxies have black holes in their core that supply the necessary gravitational energy to keep this matter in orbit. These cores also emit vast amounts of gamma radiation, which is a by-product of pair production. This emission of gamma rays from the event horizon of black holes is known as Hawking Radiation. Galactic cores are thought to be related to quasars (quasi-stellar radio sources) which existed in the early universe. They can be observed at very high red-shifts (ages of several billion light years... the highest red shift objects have ages estimated at 15 (+-5) billion light years). Single quasars can produce as much light as an entire galaxy and appear to us as faint stars in the night... sending their light from the edge of the universe (although it is highly likely that they have, since emitting the light we now see, evolved into galaxies or died out, whichever is their course of evolution).

Cheers,

Timkin

centre of the galaxy is made up of dark matter.
the mass of the centre is very high, but little common matter.

another posibility is black holes, but then this is in dispute, because black holes can be detected with radio waves and there is not enough matter in the centre.

i think its dark matter..

Its my duty, to please that booty ! - John Shaft

quote:Original post by jwalker
centre of the galaxy is made up of dark matter.

Dark matter is just a convenient explanation for us not understanding how the visible matter in our galaxy (and many others) accounts for only 10% of the necessary mass to hold the galaxy together. That is, the galaxy would need to be 10 times more massive than observations suggest it is to account for the angular momentum observed in the galactic disk. Dark matter is one explanation of this ''unobserved mass''. However, it could be equally likely that our understanding of general relativity is incomplete and that you don''t need all that mass to hold the galaxy together! If special relativity taught us anything it''s that our perceptions and hence the mathematics we derive to explain the universe in our local environemnt (i.e. low speeds) don''t scale up to the universal environment (i.e speeds greater than 1/5 c in the case of special rel).

Until someone discovers a WIMP or discovers a far higher density of MACHO''s, I''ll remain sceptical about dark matter!

Cheers,

Timkin

quote:Original post by Mulligan
What exactly is in the center of a galaxy? Its a big bright buldge, but is that just a high concentration of stars? If it is something else?

A chewy caramel nougat.


Don''t listen to me. I''ve had too much coffee.