Cosmic Odyssey question- cause of star size

[newtonian]

It is airing right now on the Science Channel, 193 on Dish network, 284 on Direc Tv.<br /><br />On this program it was noted that the sizes of stars forming in the Eagle nebulae (as we observe them, time delay) is determined by when they leave the 'nest,' or protective cloud in which they are forming.<br /><br />And also how close massive stars with strong solar winds and UV radiation are.<br /><br />In another thread I explored the average star size changing with the average Jean's mass in our universe.<br /><br />Ckearly it is not that simple.<br /><br />So, you all, what are some causes of star size?<br /><br />BTW- Cosmic Odyssey will be rebroadcast this afternoon.in 2 hours, 2:00 Central Standard Time (3:00 EST), United States.

 

[Saiph]

AFAIK, its a function of pressure and density. The more pressure a cloud exhibits (likely due to ambient temperature) the smaller a stars going to be (it'll break up sooner). The density (and also the uniformity of this density) can also play a factor. Very dense, but very uniform, leads to lots of small stars. Not very dense lead to few stars. Dense, but in big chunks, can foster bigger stars.<br /><br /><br /><br />During formation, it's basically a race to pile on as much stuff as possible, before the fusion ignites, and the repeling UV field gets into place (by that I mean the star heats up the gas, causing expansion to counter the gravitational contraction via UV light). <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[newtonian]

Saiph - That's what I thought. However, the broadcast showed photos of stars that look like comets! Their accretion disks are being blown away, not by their own solar wind, but by the solar wind from other stars.<br /><br />"Protostars become exposed to a harsh wind of ultraviolet radiation from the massive suns born earlier. The gale of radiation threatens to blow away the vital gases these stellar embryos need to grow. It might even rob them of their chance to become stars at all. Apparently in the Eagle's nest not every hatchling survives... at an arbitrary place in that process along comes the hatchett- that's all you get- and that's now the size that star is going to be - its not going to grow any larger becsause it doesn't have anything to grow from. And so we are seeing the process - we are seeing at least one of the processes - that determines the sizes these stars actually reach. So both the Orion nebula and the Eagle nebula are showing us a smoking gun..." - Cosmic Odyssey broadcast.<br /><br />So young hot massive stars have quite an effect. It is not as simple as average density in the cloud, let alone average density in the universe.

 

[alokmohan]

Protostars are rather fishy guys.

 

[newtonian]

alokmohan- come again?<br /><br />Well, my question could be extended to include:<br /><br />Would the variable environments at star formation cause the following properties to be variable?<br /><br />1. Internal rotational differences.<br />2. Resulting internal magnetic fields.<br />3. Rotational speed and direction.<br />4. Percentage of various elements such as hydrogen, helium, and heavier elements in core and surrounding layers at conception (= beginning of fusion radiation light)<br />