View Full Version : Simulation Casts Doubts on One Theory of Star Formation

2005-Nov-17, 04:22 PM
SUMMARY: Astrophysicists at Lawrence Livermore National Laboratory have developed a computer simulation that fails to support one of two major theories of star formation: the competitive accretion model. In this model, clumps form in hydrogen clouds which then collapse to form stars which compete with surrounding stars for material. The simulation showed that turbulence around the newborn star would prevent additional material from falling into the star.

View full article (http://www.universetoday.com/am/publish/doubts_alternative_star_theory.html)
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2005-Nov-17, 07:14 PM
It all sounds very adversarial in the eyes of these guys. One large hole in their contention, as I read it, is that the model they are using has some form of added turbulence in order to support the big-core theory, and it appears that this exact contribution is what is stopping the core-accretion theory from working in their simulation.

Hopefully they can get away from the "winners and losers" idea and come up with a more flexible approach which acknowledges (as they hint) that both mechanisms could be active under different conditions to different degrees.

2005-Nov-18, 01:18 AM

the results of star formation processes are open clusters. If you study young open clusters it is evident that only a fraction of the gas cloud from which the cluster developed ends up in the cluster stars. Further, most of these cluster stars have low masses, and they usually rotate at very different speeds.

The competitive model of star formation assumes that stars while they form accrete matter from their surrounding environment und thus grow in mass, until the massive stars start to produce strong stellar winds which then blow gas und dust out of the field of the cluster, thus putting an end to all the accretion processes there. Such, the accretion process of the low-mass stars ends, too, and thus these cannot attain higher masses.

But I think that it is common in currents that they are turbulent, as it is less likely that every particle in a large flow of particles will permanently move at exactly the same speed. Watch the movements of particles in the flows which you can observe (Rivers, clouds in the wind, ...) !

I think it is wrong to keep turbulences out of the consideration. Turbulences break an existing flow up in different areas, each with a different speed and different directions of flow. Each of these may have a different momentum of rotation.
In interstellar molecul clouds, such areas may result in building stars of different masses and of different speeds of rotation. The surrounding areas with different turbulences may carry matter away from the locations where accretion processes are active. There is no need for a stellar wind to stop the accretion process.

I think, that both theories may be right, one for one type of a cluster, the other one for the other type of a cluster, and for some clusters, even both.