Galactic Fossil Found

jazzyseth writes "This story on Nature.com's website reports "Astronomers have discovered a star on the outskirts of the Milky Way that may represent those that filled our Galaxy, and perhaps the Universe, with the chemical elements around us. This fossil from the early days of our Galaxy contains virtually no metal." Here is another link to an article on the BBC website describing the discovery of our galaxy's "oldest star"."

Comments

How exactly

[sweetooth]

do we determine that this star contains no metal? The articles are a bit short on details.

Re:How exactly

[dunkelfalke]

analyzing the spectrum i suppose

Re:How exactly

[ThorGod]

2 words: Spectral Analysis
When any element gives off light, as the elements which make up a star do, it gives off light in such a way that it's unique to every element. It's been a while since I studied this so I have to be brief on details, but I hope you get the idea. If not do a google search on spectral analysis.

So...

[khaladan]

This post contains no metals.

This whole article is OT

[L. VeGas]

Here is another link to an article on the BBC website describing the discovery of our galaxy's "oldest star"

Why are we posting articles about Joan Rivers on /. ?

Question asked in article

[jonnyfish]

Why have no stars been found between 1/10,000 and 1/200,000 of the Sun's metal abundance?

Since I know next to nothing about hardcore physics, I have to ask: how long do we think it took for "mostly hydrogen, some helium, and a little lithium" to be converted into all of the naturally occuring elements of today? Is there any possible known explanation for the question asked in the article?

Re:Question asked in article

[redcliffe]

Fusion. Helium is produced when Hydrogen fuses, the Lithium is produced when helium fuses, etc.

Re:Question asked in article

[geoswan]

Since I know next to nothing about hardcore physics, I have to ask: how long do we think it took for "mostly hydrogen, some helium, and a little lithium" to be converted into all of the naturally occuring elements of today?

I am not an astrophysicist. But I think I can tell you where the other elements are made, and how they are spread.

I believe the short answer is supernovae.

The fusion of atomic nuclei of the elements low on the periodic table generates energy. The Fusion of Hydrogen to Helium generates the most energy per nuclei produced. And it happens at a lower pressure and temperature. The energy produced keeps the gas hot enough that gravity does not pull the star into a denser ball.

As time goes by, and Hydrogen is fused to Helium, the star's core starts to become mainly Helium. At high enough temperatures and pressures the Helium starts to fuse, and the innermost core gets composed of those elements.

Iron is the element where Fusion no longer produces energy, but rather takes energy. In stars like our Sun, that is all that happens, eventually all the fuel that is at a temperature and pressure dense enough to fuse has fused, and the star goes dim.

Note, all the really common elements we find here on earth, in the atmosphere, on in the Earth's crust, are the elements that are lighter than Iron, like Silicon, Aluminum, Oxygen, and so on.

The smaller a star is, the more miserly it fuses, and the longer it lasts. Large stars burn quickly, much more quickly.

Stars that are larger than, um, 1.5 times the mass of the Sun, IIRC, are large enough that when all the fuel in the core has fused, they go supernovae. This generates as much energy as the rest of a Galaxy like our own. That is a terrific amount of energy. There is enough energy there to fuse the Iron and other metals into Gold, Silver, Lead, Palladium, Plutonium, Californium, and Unobtainium. And there is enough energy to blow some portion of the star away in a huge blast wave. That shell of star detritus contains some of those higher elements. That shell is travelling far less than the speed of light, but pretty fast by celestial standards. And as it expands and dissipates, it leavens star forming dust clouds with the higher elements.

Really big stars don't last billions of years, like the Sun, they last only a billion years or so. And really, really big stars, would last even shorter times. So how long would it take for a galaxy sized gas cloud that already had some metal poor stars form to get sprinkled with metals, for the next generation of stars that have some metals?

Jeez, I don't know. I am not an Astrophysicist. Okay, okay, my wild guess... Well let's see, our Galaxy is 100,000 lightyears across. How fast does that shell of detritus shoot out from the supernovae? 1% the speed of light? 0.1% the speed of light? 0.01% the speed of light? But the detritus doesn't have to spread through the entire galaxy, because there would be lots of Supernovae. We have three per 1000 years now. Who knows what the rate was then? But, let's say it was the same as now. Once they start popping off (100 million years?) a few tens of millions of years and we would have tens of thousands of supernovae blast waves leavening all those star forming dust clouds.

What happens when a dust cloud that has some metals, but not many, forms a stellar system? Do you still get planets the size of Jupiter? Or do all the planets get downscaled, so instead of Jupiters you get Neptunes? Would the inner planets get downscaled too? Or maybe you just get inner planets, of similar sizes to ours, and no big gas bag planets at all?

I'd like to know this. Of the 100 or so stellar systems Astronomers think they have detected nearby I believe all the planets detected have been big gas bags. Some of them were 10x the size of Jupiter. And some of them were quite close their Primaries. Before they found those close-in big gas bag planets, didn't Astronomers think big gas bags only formed out where it was cooler?

Mother in Law

[lostindenver]

All they had to do is ask my Mother in law How old things are she makes this Fossil look YOUNG!!