I heard some scientist said that our galaxy, the Milky Way was not a fully form galaxy. In that case, what is the requirment to be consider to be a fully forming galaxy? and what does a mature galaxy looks like?

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It would help to get a context for this statement, because it could mean a lot of things. Generally, it is elliptical galaxies, which have no more star forming regions, or spiral arms that are considered the most mature, but it is possible he meant something else.

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Yeah. But, I think our galaxy's very mature! <_<

Then how do you explain all the whining and tantrums

I think in the future we will not look at ellipticals as muture galaxies as much as them being dead galaxies. The Milky Way began forming with the first galaxies in the universe, but it has never had its dust and gasses stripped out of it by the energetic plasma of a monster galaxy.

This is part of my dispute with the original statement in this thread.

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Sigh :huh: does a galaxy with only dwarf stars can be consider to be a mature galaxy... Only dwarf stars either in the boulge, arms, despite their shape?

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Anton, I think that's because the Milky Way is a monster galaxy.

The milky way is not a monster galaxy!

It is decent enough, unless you are talking about the Canis Minor and Sagittarius Dwarf getting ripped apart by it. An that is their own fault for getting too close, same with the maggellenic clouds.

antoniseb, do you think we will find ellipticals that have collapsed into large black holes? giving rise to Great Attractor phenomenon? If not, what happens?

Tiny, I haven't heard of brown dwarfs in any galactic bulges, I think they are full of mainly Red Giants like Betleguse, This story from science daily suggests this could be up for reveiw.

The distence to the bulge would male it prohibitative to see dwarfs, I know of a white dwarf being spotted in a globular culsters ( M4 at APOD )
But I think it is a safe bet they are there, and lots of them.

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You're right that the Milky Way is not the sort of monster I was speaking of. Many large clusters of galaxies have a giant elliptical in the centers. These monsters have central black holes around a thousand times as massive as the one in our center. There was a story a month or so ago about a galaxy falling in toward the center of one of these clusters and getting the gas and dust blown out of it.

These clusters have relatively dense very hot plasma blowing out of them. What is left after a smaller galaxy gets blown out is a collection of stars and dark matter, and no new stars are formed in that galaxy after that. Such a galaxy will fairly rapidly become an elliptical.

I believe that it is very unlikely that any of the stars of an elliptical will suddenly lose their orbital momentum and fall in to a central black hole. The outer stars will get tidally ripped away from the smaller galaxy by a bigger one, but the inner stars will remain nearly undisturbed.

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Does the shape of a galaxy (elliptical , spiral .. etc.) affects its age, gravitational force and density?

I'd have to say that it is the other way around. A galaxy's shape is determined by its age, density, gravity distribution, and the amount of material falling into it.

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I think spiral galaxies are more "mature" than elliptical or irregular galaxies, but the arguement about how many old stars are in the galaxy is a good measuring stick too.

I saw a story on Universe Today that said the Milky Way was formed soon after the Big Bang. They could tell this by the amount of Beryllium in the stars of the Milky Way. That would make us "mature" I think, unless the entire Universe is not yet mature.

My avatar is of M51. All the red stars in the arms show that this is probably an "old" Galaxy.

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Are spiral galaxies just Ellipticals with arms...or are Ellipticals just spirals with a bulge but without the arms?

Elipticals and irregulars may evolve into spiral galaxies. Elipticals aren't ripe yet.

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Ellipticals do not have gas and dust clouds. The in-fall of these is what creates the spiral arms and a steady stream of new stars. You could think of Ellipticals as being like the bulge and halo without the arms. Irregulars are generally very new galaxies, or merging galaxies.

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