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If our Sun was formed in a nebula....


UTMonkey
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Im certainly no expert in this but my guess is that the gasses that formed the nebula will continue to form other stars etc until they are all used up. A very simplistic explanation that may not be entirely correct :o

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Generally the most massive stars in the cluster that included the young sun will clear out the remaining gas via radiation pressure and/or stellar winds (depending on how massive the cluster was).

After five billion years and a couple of dozen orbits around the galaxy, both any remnants of the nebula and indeed the natal cluster itself are long dispersed.

Edited by Ben Ritchie
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As I understand it, it would almost certainly have been more than a single star that formed in the nebula. Some of the material would have condensed to form the other bodies in the Solar System and possibly satellites around other stars as well. The remaining cloud would have been displaced by the heat from the new stars and gradually cooled and dispersed into the interstellar medium.

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I recall reading that only around 10% of any condensing nebula will create stars. The remainder will get blown away by the various solar winds from the newly formed stars and simply joins the general dust that surrounds and is in our galaxy.

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After five billion years and a couple of dozen orbits around the galaxy, both any remnants of the nebula and indeed the natal cluster itself are long dispersed.

Just like adding milk into a cup of tea and stir. The milk become well disperse after a few revolution in the cup.

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The typical nebula has a natural rotational motion. Something disturbs the equilibrium to cause a star to condense out of the cloud; could be a passing star, or a nearby nova, anything to get the local density high enough that gravity overcomes the rotation of the cloud, and a star condenses. If the star is not terribly big, the pressure of the ignition of it's nuclear fusion will push local gas out of the way, but will also become a pressure wave triggering more star formation. Like the Trapezium in the Orion Nebula hollowing out a hole in the cloud, or the wave of cluster formation in progress across the face of the Lagoon Nebula; Trapezium elements are so huge that they just blew out the area, but Lagoon is more benign.

The open cluster is formed, and the stars have an initial relative rotation equal to the rotation of the host nebula. But now they are discrete lumps; no longer does a smooth field of gravity hold all the gas molecules captive and in rotation; the stellar elements formed over the early life of the cluster now disperse, starting with the initial relative motion but slowly dispersing like a CD developing cracks. The smooth gas cloud holds itself together, but once the lumps form they don't have quite the influence so the young cluster will gradually leave the nest. Depending on the history of the nebula, there may have been progenitor stars that went through end of life processes either benignly like planetary nebulae, sneezing their outer layers off at the end of life and populating the cloud with the debris of the nuclear fusion, or catastrophically in a nova or supernova. PNs will actually generate a lot of the elements starting with helium and continuing on to nitrogen, oxygen, carbon, etc., the exact forks taken depending on the initial size and chemistry of the star. To get elements heavier than iron, it takes a nova or supernova to provide enough temperature and pressure to do the alchemy. So, back to our cloud, there might have been the residue of older stars going through their end of life and leaving other elements present to become comets or planets, or only the star forms without planetary source debris. So, you have a cloud of hydrogen and perhaps other material, something causes local density to increase and start star formation and perhaps planetary formation, the outward pressure either blows the remaining gas away or merely kicks off more stars to become an open cluster, and the stars travel on their merry way under the effects of the gravity fields in their region.

For the last two years or so, the scientific publications have been presenting the argument that the Sun's motion, when tracked backwards, indicates it did not form in the Milky Way but in a satellite galaxy that is most likely now canibalized. And now that supermassive black holes have been found in many globular clusters, these appear to be the cores of canibalized galaxies.

Anyone for a ride in a time machine?

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For the last two years or so, the scientific publications have been presenting the argument that the Sun's motion, when tracked backwards, indicates it did not form in the Milky Way but in a satellite galaxy that is most likely now canibalized. And now that supermassive black holes have been found in many globular clusters, these appear to be the cores of canibalized galaxies.

I like that, i've not heard it before.

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If I'm not mistaken (a big 'if') then then Ben's point about the radiation pressure from the young stars repelling their parent cloud through radiation pressue, stellar winds, etc, might be what we see in the Rosette Nebula. Is the cluster NGC2244 excavating that central cavity that we see? Perhaps the Rosette is really roughly spherical though it looks like a thick ring from here. This is often the case in asto objects where you need the thickness of the circumference to make the gas visible. It is often too tenuous to show when seen directly in line of sight.

Olly

1013289628_hS3L7-M.jpg

Edited by ollypenrice
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You're quite right, Olly. Not sure about the specific kinematics of the Rosette, but you see young clusters carving out cavities in the surrounding gas.

Taking a couple of fairly extreme examples, e.g. this one from Spitzer with a young, massive cluster called Westerlund 2 (around 1-2 million years old)

wd2_irBoxFoV.jpg

and after a few million years more there's no intracluster gas left at all, e.g. this one at 4-5Myr (note that although the stars appear red, they're actually almost all blue supergiants)

eso1034c.jpg

The gas gets expelled by the radiation field and also stellar winds (e.g. the integrated energy of a Wolf-Rayet wind over its lifetime is not that far short of a supernova - the lower cluster has 25 Wolf-Rayets in it). Then, later on, supernovae blow out anything left (the lower cluster has likely hosted a couple of dozen of these too over the last million years, the top cluster is too young). So at the high-mass end you very efficiently shed the gas the cluster formed from. Takes a little longer for lower-mass clusters, but fundamentally similar.

Edited by Ben Ritchie
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