neil wrote:That our sun is third generation is not written in stone.
Correct. The estimate is second or third generation, but more is possible; just less likely.
We know that it's at least a second generation star due to some of its atomic components, because some of those components (things more dense than iron) can only be produced by the collapse of super massive stars (usually resulting in supernovae).
If the first and second generations of nearby stars were an even distribution of O, B, A, F, G, K and Class M stars: then which generation our Sun is, is meaningless in my opinion. Neil
neil wrote:The lack of nearby compact stars argues that Our Sun is 2nd generation that just happened to get more than it's share of heavy elements from a nearby first generation super nova. Neil
Not quite... You are assuming that our companion stars and dust clouds have remained near us, and this is not the case.
Our sun has orbited the galaxy over 20 times since its birth (over 5billion years ago), and during that time it has wandered greatly amidst its companions. The remains of the progenitor stars (black holes and neutron stars among other things) that expelled the dust that now forms us have long since been dislocated in space relative to our Sun. The debris fields have collapsed many times and been mixed quite thoroughly.
To us, the galaxies appear ordered and stable, but over the course of eons, they flow and change dramatically. Many galaxies even collide with each other:
http://antwrp.gsfc.nasa.gov/apod/ap040612.html
Perhaps you heard me screaming at Bill Gates as my 4 posts above were lost as a single post when able2know logged me out while I was typing. I figure everything that goes wrong is the fault of Bill Gates as every one is all but forced to make their programs compatable with the whims of Bill Gates. Neil
I forgot the rate of galaxy rotation, but 20 times in 5 billion years seems too fast = 4 times per billion years. circumference 30,000 light years from center = 188,400 light years multiply by 4 = 753,600 light years per billion years. Multiply by 6 trillion and divide by one billion = 4,521,600,000 miles per year.
We seem to agree, 3d generation is mostly meaningless unless most of the galaxy was stars a bit more than one solar mass in the first and 2nd generation. Is the lack of compact stars nearby at present, a coincidence, failure to detect them or some of each.
Your lots of churning hypothesis suggests that we could detect a compact star (born billions of lightyears away) heading for the inner solar system this year to arrive in 2012 or even sooner? Neil
Re: Giant planet systems.
SCoates wrote:Okay, I was having a conversation with my brother and we couldn't come to a conclusion. Is it possible for a solar system to have a giant planet at its center, rather than a star? Obviously it wouldn't be called a "solar" system any more, but is the configuration possible, regardless of its name?
Hey!
I think it is possible like the earth having the moon circulating around. But we wouldn't be able to see them. It would be dark matter and dark energy with the configuration of the solar system. :wink:
NickFun wrote:Nothing of this nature has even been viewed and I doubt you will find anything in any solar system that will match or exceed the size of its sun.
Hi!
We don't see dark matter but it is there. It is perceived.
