When a cloud of gas reaches a critical density, thermonuclear reaction occurs and a star is born. all other gas is blown away by the staller wind. So how do we get stars so much more massive then the sun?
Yes Sophie, that's right. See the following paper. Shape is related to the ability to shed angular momentum.I have read that the angular momentum of the original nebula is relevant.
Perhaps it would be hard to measure but it would be good to know if the distributions of rotation rate of stars actually correlates with their masses.Yes Sophie, that's right. See the following paper. Shape is related to the ability to shed angular momentum.
I could only read the abstract but does the paper deal with angular momentum? (It may be implied in some of it ). I guess it is not unreasonable to expect fewer really big ones. The main conclusion could be looked on as 'obvious' but then - nothing in cosmology is really obvious.For further discussion see; https://arxiv.org/abs/astro-ph/0205466, The Stellar Initial Mass Function and Beyond
Does this link work? It takes my computer/connection about 2 minute.I could only read the abstract...
My impression was that higher rotation rates increase the velocity of the stellar (main sequence) wind because of the magnetic field continues to accelerate particles. The stellar wind and interaction with interstellar gas carry angular momentum away from a star. Higher rotation main sequence stars are not ejecting that much more mass in the wind. With pre-main sequence stars something similar should happen. Herbig-haro objects are ejecting mass in a jet perpendicular to the spin axis. High rotation decreases pressure on the core which should decrease the nuclear reaction rate in the core. Also a flat object can radiate heat better than a spherical object....does the paper deal with angular momentum? (It may be implied in some of it ). I guess it is not unreasonable to expect fewer really big ones...
The pressure inside the nebula would be higher if the nebula is spinning slower. The R136 cluster has a mass of around 90,000 solar. The Tarantula Nebula was able to form the large stars in R136 because of compression. The Tarantula Nebula has around 450,000 solar mass. Most of the nebula will not end up as planets.I have read that the angular momentum of the original nebula is relevant. The proportion of the nebula that ends up as part of the star will depend on the rotation rate (slower would produce bigger) whilst the rest of the material will end up as planets, to account for the surplus angular momentum. I always wondered about this because, if it were true for established stars, there could be some very oblate stars about (only just hanging together), as far as I can see.
Perhaps this is nonsense? Someone on PF must know about this idea.
The collapse occurs. The mass of the main sequence star is determined by the size of the cloud fragment. The cloud fragment's mass is much larger than the mass of the star it will become. All stars including brown dwarfs and type-Os will blow away a lot of gas as they collapse. Most of that blow out is finished when nuclear fusion. begins.When a cloud of gas reaches a critical density, thermonuclear reaction occurs and a star is born. all other gas is blown away by the staller wind. So how do we get stars so much more massive then the sun?
Actually, it has been easy to measure stars' angular momentum for many decades: Even if you can't resolve the stellar disk, you can measure the width of spectral lines. Rapid rotation produces broad lines, just because the Doppler effect on one side of the disk will red-shift each line somewhat, and on the other side, blue-shift it. (Other effects can broaden them, too, but each effect produces a characteristic kind of broadening, so sufficiently precise measurements can distinguish the causes.)Perhaps it would be hard to measure but it would be good to know if the distributions of rotation rate of stars actually correlates with their masses.
The situation for stars could be a bit different from that of objects without significant internal energy generation to 'pump them up.'
You recall correctly. High mass stars rotate faster. Old stars rotate slower and high mass stars do not become old. You can use a star's rotation rate to estimate the age.... My recollection is that high-mass stars (before the red-giant stage) systematically have much more rapid rotation rates than the rest, though I have not followed that literature since pre-Hubble days. The speculation at that time was that lower-mass stars might, for whatever reason, systematically produce planets to a degree that high-mass ones did not; of course, with Kepler, we now have vastly better statistics on that.
You're misreading this article that you've posted - The value of 0.15 that you quote, is a RATIO, and the fact that it doesn't change from low mass to high mass stars just means that there's no different mechanism for forming low mass or high mass stars as explained in the article. Moreover, this ratio between "observed rotation rate" and "equatorial breakup velocity" being constant means that, since the "equatorial breakup velocity" increases with increasing mass,then the "observed rotation rate" also increases with increasing mass, which shows that there IS a correlation between angular momentum and stellar mass.This paper appears to put to rest any doubts about the role of angular momentum in the formation of massive stars; https://arxiv.org/abs/astro-ph/0604533, What Sets the Initial Rotation Rates of Massive Stars? Note in particular this assertion: "We find that the median of the quantity v_obs/v_c (observed rotational speed/equatorial breakup velocity) is typically about 0.15 and shows no evidence of a discontinuity over the full range of stellar masses...:"