Starship Asterisk*

Is there been information regarding the chemical composition of the dust that is often seen as dark patches in the Hubble images?
Presumably the dust is the basis for new star formation and it would be interesting to learn what is in the dust prior to star formation.

Thanks for any thoughts.
Bill

bill-friedlander wrote:Is there been information regarding the chemical composition of the dust that is often seen as dark patches in the Hubble images?
Presumably the dust is the basis for new star formation and it would be interesting to learn what is in the dust prior to star formation.

Actually, dust is not a significant component in the material making up new stars. Stars are formed from hydrogen, and the role of dust seems limited mainly to catalyzing the initial collapse and affecting the dynamics of that collapse.

The dust itself is mainly made up of silicates, containing carbon, oxygen, iron, and all the other elements produced when a star explodes.

Chris Peterson wrote:

bill-friedlander wrote:Is there been information regarding the chemical composition of the dust that is often seen as dark patches in the Hubble images?
Presumably the dust is the basis for new star formation and it would be interesting to learn what is in the dust prior to star formation.

Actually, dust is not a significant component in the material making up new stars. Stars are formed from hydrogen, and the role of dust seems limited mainly to catalyzing the initial collapse and affecting the dynamics of that collapse.

The dust itself is mainly made up of silicates, containing carbon, oxygen, iron, and all the other elements produced when a star explodes.

This is a case where one question's answer leads to another question. Sol is a later generation star, and therefore we benefit from having handy things like oxygen, carbon, iron, gold, etc., all of which were produced in earlier generation stars and then blown out into the clouds where they could become part of another star. But if "Stars are formed from hydrogen, and the role of dust seems limited ...", then where did all our carbon, etc. come from?

Rob

rstevenson wrote:This is a case where one question's answer leads to another question. Sol is a later generation star, and therefore we benefit from having handy things like oxygen, carbon, iron, gold, etc., all of which were produced in earlier generation stars and then blown out into the clouds where they could become part of another star. But if "Stars are formed from hydrogen, and the role of dust seems limited ...", then where did all our carbon, etc. come from?

While from our perspective it seems like there's a lot of carbon (and other heavy elements as well), the fact is that when you look at the Solar System as a whole, it is 91% hydrogen and 8.9% helium. All the heavier stuff (mainly oxygen, carbon, nitrogen, neon, and iron) occupies the last 0.1% of the Solar System's atomic distribution (in terms of mass, hydrogen is 71%, helium is 28%, and the remaining elements are 1%).

We just happen to be sitting on a huge concentration of everything but hydrogen and helium. But the molecular cloud the Sun formed out of could reasonably be described as a slightly contaminated hydrogen cloud.

Thanks Chris. It's so hard to keep in mind the scale of things relative to us carbonites.

Rob

rstevenson wrote:Thanks Chris. It's so hard to keep in mind the scale of things relative to us carbonites.

Rob

Rob, people are mostly water and water is mostly hydrogen(H2O), so even though people may be carbon based, shouldn't we be called "Hydro's" and not carbonites?? Of course if one uses both terms - then we would be "HydroCarbons", but that would seem to be another story altogether.

beyond wrote:Rob, people are mostly water and water is mostly hydrogen(H2O), so even though people may be carbon based, shouldn't we be called "Hydro's" and not carbonites?? Of course if one uses both terms - then we would be "HydroCarbons", but that would seem to be another story altogether.

Closer to carbohydrates than hydrocarbons. Same basic ingredients, very different compounds.

Chris Peterson wrote:The dust itself is mainly made up of silicates, containing carbon, oxygen, iron, and all the other elements produced when a star explodes.

rstevenson wrote:This is a case where one question's answer leads to another question. Sol is a later generation star, and therefore we benefit from having handy things like oxygen, carbon, iron, gold, etc., all of which were produced in earlier generation stars and then blown out into the clouds where they could become part of another star. But if "Stars are formed from hydrogen, and the role of dust seems limited ...", then where did all our carbon, etc. come from?

As Rob says..."one question leads to another".....Thus: Where do the rocks etc. which we see as asteroids, planets, etc. also come from. These must not
start as hydrogen?? I suppose that they accrete from the accretion disks that surround new stars??, but still where do the rocks that probably formed the earth
start out??

....Bill

bill-friedlander wrote:As Rob says..."one question leads to another".....Thus: Where do the rocks etc. which we see as asteroids, planets, etc. also come from. These must not
start as hydrogen?? I suppose that they accrete from the accretion disks that surround new stars??, but still where do the rocks that probably formed the earth
start out??

The dust accretes separately from the gases, at least at certain stages of a stellar system's evolution. Presumably there's a point after stellar fusion begins where winds push away most of the gas remaining in the accretion disc, especially in the inner system. All that's left is the denser, less volatile heavy elements, in the form of dust and planetesimals, which continue to accrete into terrestrial planets. The result is a few planets and a lot of asteroids. Material smaller than a meter or so doesn't have a long lifetime (compared with the Solar System), so it is being continually swept into the Sun, and replaced with new material from collisions of larger bodies.

Rocks start as silicate dusts, not as hydrogen.