gravitational collapse. And for a long time there has been some evidence to support the idea.
Over the past decades, thanks to ever sophisticated instrumentation and data processing abilities, scientists have been able to address questions regarding the nitty-gritty of the process. However, one observation has always been somewhat elusive, namely the infall of material from the surrounding gas and dust cloud, toward the protostar itself.
For a while now, and somewhat to everyone's surprise, paradoxical outflows from collapsing stars have been observed. Inflows have been another matter altogether. There has been evidence of these processes but it has never been conclusive.
Now, thanks to even better technology, particularly satellite instrumentation, the situation is beginning to change.
The following paper reports on some key observations regarding this:-
Waterfalls around protostars: Infall motions towards Class 0/I envelopes as probed by water
The paper is technical and hence a slog, but enough of it is understandable by a layperson such as myself to get something from it. For those of you who have a better understanding of physics, particularly of the physics as it relates to this kind of study, well hopefully you will get even more from it.
Some points are:-
1) To go from the interstellar medium to a gas cloud, the density must increase from around 0.001 ions (atoms) per cc to around 10,000 ions per cc. To go from the gas cloud to a very dense clumps within a cloud, the density must increase form around 10,000 ions per cc to 1,000,000 ions per cc. But to get from the dense clump to the star, the density has to go from 1,000,000 ions per cc to 1,000,000,000,000,000,000 ions per cc. Ouch!!!
2) The formation of the protostar by gravitational collapse is what is thought to bring about this massive increase in density.
3)A gas cloud is rotating and as matter moves in towards the central dense globule (the future star), it picks up rotational velocity and eventually enough of this gas forms a flattened disk which orbits the star. It is thought that gas then falls from this disk into the future star. This disk may be stable or it may be unstable.
4) So, in general, there are three major components - a large external enveloping cloud from which matter falls onto a flat accretion disk which orbits a central dense globule which later becomes the star. Matter falls from this accretion disk onto the globule and when the globules density is high enough, it becomes hot enough to be a star.
5) Another component, already mentioned, is an outflow - a strong beam of material escaping as a jet from each pole of the cocooned protostar.
6) Various molecules are used to follow the motions of gas within the cocoon that encloses the protostar. With respect to infall, the molecules are CS, HCO+, N2H+2Warning
For those who are as afraid of stars being able to form naturally as they are afraid of extra solar planets, best not to open this at all.
Over the past decades, thanks to ever sophisticated instrumentation and data processing abilities, scientists have been able to address questions regarding the nitty-gritty of the process. However, one observation has always been somewhat elusive, namely the infall of material from the surrounding gas and dust cloud, toward the protostar itself.
For a while now, and somewhat to everyone's surprise, paradoxical outflows from collapsing stars have been observed. Inflows have been another matter altogether. There has been evidence of these processes but it has never been conclusive.
Now, thanks to even better technology, particularly satellite instrumentation, the situation is beginning to change.
The following paper reports on some key observations regarding this:-
Waterfalls around protostars: Infall motions towards Class 0/I envelopes as probed by water
The paper is technical and hence a slog, but enough of it is understandable by a layperson such as myself to get something from it. For those of you who have a better understanding of physics, particularly of the physics as it relates to this kind of study, well hopefully you will get even more from it.
Some points are:-
1) To go from the interstellar medium to a gas cloud, the density must increase from around 0.001 ions (atoms) per cc to around 10,000 ions per cc. To go from the gas cloud to a very dense clumps within a cloud, the density must increase form around 10,000 ions per cc to 1,000,000 ions per cc. But to get from the dense clump to the star, the density has to go from 1,000,000 ions per cc to 1,000,000,000,000,000,000 ions per cc. Ouch!!!
2) The formation of the protostar by gravitational collapse is what is thought to bring about this massive increase in density.
3)A gas cloud is rotating and as matter moves in towards the central dense globule (the future star), it picks up rotational velocity and eventually enough of this gas forms a flattened disk which orbits the star. It is thought that gas then falls from this disk into the future star. This disk may be stable or it may be unstable.
4) So, in general, there are three major components - a large external enveloping cloud from which matter falls onto a flat accretion disk which orbits a central dense globule which later becomes the star. Matter falls from this accretion disk onto the globule and when the globules density is high enough, it becomes hot enough to be a star.
5) Another component, already mentioned, is an outflow - a strong beam of material escaping as a jet from each pole of the cocooned protostar.
6) Various molecules are used to follow the motions of gas within the cocoon that encloses the protostar. With respect to infall, the molecules are CS, HCO+, N2H+2Warning
For those who are as afraid of stars being able to form naturally as they are afraid of extra solar planets, best not to open this at all.
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