Starship Asterisk*

neufer wrote:

rstevenson wrote: Unlike galaxies, globular clusters have sublety.

sublet: Property leased by one lessee to another.

rstevenson wrote:

Note to self: Never give Art an opening. Always use the speel chacker.

Rob

rstevenson wrote:Note to self: Never give Art an opening. Always use the speel chacker.

Rob

Oh, Rob, you know Art: he'll make his own opening if no one gives him one! Think of providing an opening as channeling the energy in the direction you want it to go, rather than... well, you know...

rstevenson wrote:
Note to self: Never give Art an opening.

But you're a donut

Beautiful! I just wonder what it would be like to be on a planet inside the cluster and look up at night sky. It would have to be mind blowing!

Jim

Chris Peterson wrote:

neufer wrote:Then how do you explain the spherical symmetry of globular clusters

Spherical symmetry doesn't argue against gravitational forces being the primary factor in the formation of a many-star body, whether a galaxy (and there are spherical galaxies) or a cluster.

I'm not trying to describe any detail about how galaxies or clusters form (it's an area of active research, of course), only arguing that in the broadest of terms, gravity is probably the dominant force involved.

In globular clusters, if Gravity is the only dominant force, what is it doing differently from "normal galaxies"? Gravity is a known force at present. To say it is the only force is short sighted. There may be other forces involved that we have not discovered yet.

garry wrote:In globular clusters, if Gravity is the only dominant force, what is it doing differently from "normal galaxies"? Gravity is a known force at present. To say it is the only force is short sighted. There may be other forces involved that we have not discovered yet.

I don't doubt that other forces play a role. For instance, we have good reason to believe that hydrodynamic drag and electromagnetic momentum transfer effects are important in creating accretion discs in planetary systems, and possibly in galaxies. Without those effects, there is no mechanism to produce a disc, and you get a spherical halo, as we see in the dark matter surrounding galaxies. Nevertheless, gravity is dominant force in bringing these structures together.

There is no reason the same basic mechanisms can't produce different physical structures. We see that all the time. Assuming (as is reasonable) that the conditions in which spiral galaxies and globular clusters form are different, different structures are hardly surprising.

What I find incredible about globular clusters is that they are found in all big galaxies (and in some small galaxies, too), and most of the globulars are between ten and twelve billion years old. What incredible forces swept across the universe between ten and twelve billion years ago to create these amazing super star clusters everywhere in the cosmos?

Ann

Ann wrote:What I find incredible about globular clusters is that they are found in all big galaxies (and in some small galaxies, too), and most of the globulars are between ten and twelve billion years old. What incredible forces swept across the universe between ten and twelve billion years ago to create these amazing super star clusters everywhere in the cosmos?

I don't think anything "swept across the universe" to create globular clusters. It seems likely they are simply a byproduct of galaxy formation, and it is therefore not incredible at all that they are found around large galaxies. It would be much more remarkable if they existed in some galaxies but not others.