How big can red supergiants get and can they be born at that size?

[vincentm]

How big can these stars get, Also can a star be born at a Supergiant level?

I'm having a hard time understanding a particular object. The Helix Nebula is said to be the result of a supernova explosion, a closeup reveals tiny knots of gas, now these knots are said to be at least the size of our solar system, which means that the star dying to cause the Helix Nebula must've been huge, but how big was this star?

 

[DaveC426913]

According to Wikipedia, "A supergiant is a very large type of star which is ~10 to 50 solar masses on the Hertzsprung-Russell diagram. Supergiants can have radii in excess of 1000 solar radii."

 

[Gold Barz]

My question is will those knots of gas create new stars?

 

[Astronuc]

Possibly this will answer the question.

http://phobos.physics.uiowa.edu/~srs/lec16/lec16.html

Otherwise google with "Red supergiant evolution".

There are a number of pdf's and one site suggests the evolution of red supergiants is still poorly understood.

Of recent supernovae observed, how many were red sg's before.

 

[Chronos]

Based on current knowledge [which is not precise or complete] red giants evolve from HR main sequence stars. The core temperature necessary to inflate the photosphere to red giant proportions cannot be achieved by hydrogen fusion. Perhaps a star formed predominantly from helium could theoretically be born a red giant, but I doubt it could ever get hot enough to initiate helium fusion without blowing itself apart.