We are star dust ...

[Alastair Rae]

Periodic table coloured by origin of the elements:

[Capricorn]

Not sure why but it seems wrong that a super nova is needed to produce iron Fe, Iron being the point at which no energy is obtained from fusion, but a small star will produce elements way beyond iron.

Would have thought that a small star, one that doesn't go nova, would cease element production more or less at iron, some small amounts of other heavier elements from the core collapse but not in the "significant" amounts indicated.

As said just doesn't look right.

[ollypenrice]

The Magic Furnace, The story of Atoms, by Marcus Chown, is a stunning read on this issue.

Olly

[acey]

Not sure why but it seems wrong that a super nova is needed to produce iron Fe, Iron being the point at which no energy is obtained from fusion, but a small star will produce elements way beyond iron.

I don't get it either. Is the table saying that elements such as lead are produced by nucleosynthesis inside small stars? (I didn't think that was possible). Or that Beryllium first got made in cosmic rays?

Or is it saying that most of the lead now present in the universe is a decay product of heavy radioactive elements that were produced in supernovas, then were incorporated in small stars formed afterwards. And the Beryllium now present is mainly produced by cosmic rays.

In other words it shows the present abundance of elements in different types of location, rather than their primordial origin?

[symesie04]

Hmm is it saying that iron requires the force of a supernova to be released. During any other process it is therefore trapped in the very inner core and therefore unless a thrown out during the force of a supernova it would never see the light of day. Or maybe the cold of space.

[symesie04]

Upon further scrutiny very little of that makes much sense to me.

[LoneStar77]

I, too, am perplexed by the "small star" angle. But does the "large star" merely involve planetary nebulae and the like (non-supernovae stuff)?

And I guess I've had my eye on the telescope and computer too long. I absolutely did not know we'd already gotten up to element 118. Amazing!

[sologuitarist61]

Be interested to know where Alistair Rae got the periodic table as shown, and whether there were any words of wisdom printed with it - or is it a spoof - April Fools Day is just around the corner after all.

[Macavity]

I got embroiled in "r-process" (the "s-process", and more) Wiki's, but then vaguely "lost the will to live". LOL. I think a SIMPLE visual summary could be useful? But this (nucleo synthesis?) is a relatively complex field now?

Anomalous occurence of certain (heavier) elements does seem a fascinating subject.

Beyond the main-sequence star route, which only progresses as far as Fe (Iron)...

[Doughzer]

click on the pic. to get to the link sologuitarist

[K Nixon]

Hi all,

just to give you a simple version of star synthesis:

in main sequence stars hydrogen fuses to make helium. They also make lighter elements up to nitrogen oxygen and carbon in trace amounts. All the stars move onto the red giant phase but the ones about 3 times the size of the sun become red supergiants (we're an imaginative lot when it comes to naming).

This stage happened when they run out of hydrogen in the core and it builds up a solid chunk of helium.

When the stars stop undergoing nuclear fusion they cool down and contract (as things do).

When they contract they release a bucket load of gravitational energy which boosts the temperature (incidentally what causes the outside to swell up making the giant)

In sun sized stars thats about it.

In larger stars this increase in temperature enables the core to start fusing hydrogen (by a process called triple alpha) to make carbon and further fusions beyond this making larger and larger elements.

You can fuse elements together to release energy up to iron, but iron is the most stable element (in terms of nucleus anyway). You can fuse together iron to make larger nuclei but you have to put energy in.

stars will do a little bit of this but only very trace amounts.

When red supergiants build up iron in their core once more they stop fusing and cool. This time when they contract they collapse inwards. This time they keep contracting (collapsing) which produces a huge amount of energy causing a supernova explosion and also raising the temperature to such a degree that enough energy is provided to make every element in the periodic table. The explosion then sprays it across the local part of the galaxy to be combined with newly forming protostars like baby suns.

Obviously this is the really simplistic version but it doesn't quite match the periodic table above. Although exactly what elements will be made where and by what object is not up to a specific cut off point but depends on its nuclear stability.

sorry that rambled for far longer than it was meant to.

Kieron

[Joguj]

Thanks for that Kieron. Very nicely written, I re-read that explanation several times and it helped me almost picture what happens. Think I may find more reading material on star birth and death.

[K Nixon]

No probs.

A level physics books tend to cover stellar evolution but a bit too basically. 1st year undergrad physics/astrophysics books prob cover it a bit better.

However they are dull! If you like John Gribbin, he wrote a quite a nice book called, interestingly enough, Stardust. It is quite well put together and he explains all you'd want to know (more than I wanted anyway!) quite well.

K

[JulianO]

Quick correction of an typo I suspect. The triple alpha process converts Helium to Carbon, not hydrogen. Otherwise a good thumbnail sketch of the life and death of stars!

[JulianO]

I got embroiled in "r-process" (the "s-process", and more) Wiki's, but then vaguely "lost the will to live". LOL. I think a SIMPLE visual summary could be useful? But this (nucleo synthesis?) is a relatively complex field now?

The r-process is what happens in supernova explosions - the r is for rapid. There are so many neutrons flying around after the explosion that new elements can be made up very quickly - and almost any element you care to mention can be made. Up past Iron and beyond - there is a fantastic flux of neutrons, neutrinos and just general energy - so anything goes!

The s-process (s for slow) happens in late big stars, whereby neutrons are slowly (like 1 every 100 years) stuck onto existing atoms. So for example an atom of Cadmium-114 might gain a neutron. This makes it Cadmium-115 which is unstable and it decays by beta decay into Indium-115. So we've made Indium. Now if that gets a neutron - 1000 years later, it makes Indium-116 - which is unstable and decays to Tin-116. In this way elements can be made slowly over time - but because of the long period and the instability of elements with half lifes less than 1000 years, some things just can't be made this way.

[K Nixon]

yup JulianO helium to carbon - sorry!

K

[K Nixon]

I have a related question regarding this though for all you more seasoned astronomers.

Why is oxygen such a prevalent element to the extent we had oxygen filters for observations of nebulae? Its something I knew nothing about until making a quick study of filters.

K

[JulianO]

I have a related question regarding this though for all you more seasoned astronomers.

Why is oxygen such a prevalent element to the extent we had oxygen filters for observations of nebulae? Its something I knew nothing about until making a quick study of filters.

Oxygen tends to be one of the next thinks made after carbon. Its part of one of the main reactions - the CNO cycle that is one way stars burn hydrogen, so bigger stars make quite a lot of it. I'm not sure why it makes such a good filter though.

[K Nixon]

thanks.

It just struck me as odd that oxygen above all others would be used. something to do with the wavelengths it gives out perhaps? I feel a night on wikipedia coming on.

[grey]

i'd like to throw this into the mix...

stars like the sun fuse hydrogen at approx 18 million C, as their main fuel, once they expend that fuel, gravity starts to win compressing the core driving the temp up to approx 180 million C whereby helium fusion kicks in causing the star to swell, red giant phase, helium fusion produces light elements like oxygen, etc, once a star like the sun begins to produce carbon, it starts to die, becoming a white dwarf which will burn for billions of years having puffed away its outer layers (planetary nebulae), but if the star reaches 1.4 solar masses, by means of a companion feeding the (white dwarf) like in a binary system(common enough), it goes supernova (type 1A) and spews it's elements all over the place, if you have a star with upwards of 4 - 8 solar masses, well then that's a whole other ball of "wax" when that star first creates iron, it is doomed, the iron production robs fusion energy keeping the stars outer layers up and gravity wins. the core collapses at about 70 000 km per second, the outer layers come crashing onto the core rebounding out and creating all the other elements heavier than iron, hence their rarity... type 2 supernovae and in extreme cases like VY Canis Majoris you get hyper-novae where the heavy elements are more abundant...

we and everything heavier than hydrogen and lithium are stardust, atoms that make up your body came from different stars