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zuz
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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.sophiecentaur said: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.anorlunda said: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.Chronos said:For further discussion see; https://arxiv.org/abs/astro-ph/0205466, The Stellar Initial Mass Function and Beyond
sophiecentaur said:I could only read the abstract...
sophiecentaur said:...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...
sophiecentaur said: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.
zuz said: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, it works. Thanks. Plenty to get your teeth around in there!stefan r said:Does this link work? It takes my computer/connection about 2 minute.
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.)sophiecentaur said: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.'
JMz said:... 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.Chronos said: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...:"
Stars are formed when a large cloud of gas and dust, called a nebula, collapses due to its own gravity. As the cloud compresses, it becomes denser and hotter, eventually forming a protostar. The protostar continues to grow as more gas and dust is pulled in, until it reaches a critical point and begins nuclear fusion, becoming a full-fledged star.
Stars can become more massive than the Sun through a process called accretion. As the protostar continues to grow by pulling in more gas and dust, it can reach a size and mass much larger than the Sun. Additionally, collisions with other protostars or objects in the nebula can also contribute to the growth of a star.
The mass of a star is determined by the amount of material it is able to accrete during its formation. The larger the initial cloud of gas and dust, the more material a star can gather and the more massive it will become. Additionally, the location and density of the cloud can also play a role in the final mass of a star.
As mentioned before, the initial size and density of the nebula in which a star forms can greatly influence its final mass. Additionally, the location of the star within the nebula can also play a role. Stars that form in regions with a higher concentration of gas and dust will have more material to accrete and thus become more massive than stars in less dense regions.
The mass of a star plays a crucial role in its lifespan and behavior. More massive stars have a shorter lifespan because they burn through their fuel at a faster rate. They also have a higher surface temperature and emit more energy, making them brighter and bluer in color. On the other hand, less massive stars have a longer lifespan and are cooler and dimmer in comparison.