I was just wondering what type of nebula did the Sun form from because mainly there are 5 categories: emission nebulae, reflection nebulae, dark nebulae, planetary nebulae, and supernova remnants, so which of these was the Sun formed from and is there a name for this nebula? Probably M67.
2 Answers
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Stars and the planetary systems around them form from dark and dense molecular clouds.
Physically we distinguish
- Hot ionized gas (supernova remnants and emission nebulae)
- Hot neutral gas (also some parts of supernova remnants, reflection nebulae like outflows and clouds near new stars etc)
- Cold neutral gas and molecular gas (this is usually the dark nebula)
In the sky the star forming nebulae are visible as either reflection or dark nebulae. One of the nicest examples is in the Orion Nebula which is a large and close star forming region. In front of the bright nebula (it's partially a reflection nebula, some parts are actually already excited by newly-formed stars so that we see the H-alpha emissions) we see the dark blobs and the dark disks around evolving stars (e.g. here).
answered Dec 30, 2022 at 9:36
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1$\begingroup$ But why do emission nebulaes have H-Alpha emissions? $\endgroup$– user47732Commented Dec 30, 2022 at 9:47
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1$\begingroup$ That's a separate question. If hydrogen gas is excited (hot) and has emissions it can only emit radiation in the wavelength it can radiate. Each element has characteristic transition lines. H-alpha is the most prominent one of the Balmer series of hydrogen, the base transition of that is between quantum numbers n=3 and n=2 (Lyman series is to quantum number n=1 and more energetic). Other wavelengths than these discret numbers can only be emitted when you have another partner (e.g. atom) - which is rare in space which is empty in terestrial terms - even in gas clouds. $\endgroup$ Commented Dec 30, 2022 at 9:55
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$\begingroup$ What emit light (hydrogen spectral lines) in emission nebulae Is not ionized gas but gas which has just recombined. $\endgroup$ Commented Dec 31, 2022 at 22:05
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Stars are formed in molecular clouds: these are gas clouds with conditions for $H_2$ to form.
Molecular clouds are typically dark nebulae, but if there is a bright star near them, then they can reflect the light of that star and be reflection nebulae. There is no actual difference, only in appearance.
Planetary nebulae and supernova remnants are not places where stars form, as the gas is hot and moving apart. (Sun from SuperNova) Stars form where cold gas can move together.
Of course you can't see the nebula that the sun formed from, it was turned into stars 4.6 billion years ago. It doesn't exist any more. The open cluster M67 is very unlikely to be the parent cluster of the sun
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$\begingroup$ But why are Planetary nebulae hot, I know they are Ionized but why is it hot? and can gravity overcome the Hot nebulae $\endgroup$– user47732Commented Dec 30, 2022 at 9:21
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$\begingroup$ They are ionized by the intensely hot white dwarf at their centre. There is also a huge difference in size between a molecular cloud dark nebula and a planetary nebula. Stars do not form in planetary nebulae. "ionized" is another way to say "hot". It means that the gas has absorbed enough energy to strip the electron from the hydrogen. If gas is cold, then it isn't ionized. $\endgroup$– James KCommented Dec 30, 2022 at 9:25
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$\begingroup$ Thanks, @JamesK for the clarification. So gravity can't overcome the hot planetary nebulae? and what would happen to the White dwarf? $\endgroup$– user47732Commented Dec 30, 2022 at 9:34
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$\begingroup$ Thanks, @JamesK $\endgroup$– user47732Commented Dec 30, 2022 at 9:37
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$\begingroup$ It would probably cool down into a black dwarf? $\endgroup$– user47732Commented Dec 30, 2022 at 9:39