Galactic Fossil Found 16
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"."
How exactly (Score:2)
Re:How exactly (Score:2)
Re:How exactly (Score:4, Informative)
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.
Re:How exactly (Score:1)
Spectral analysis is also used to determine a star's distance and velocity.
Very fast objects will emit light at lower frequencies -- a redshift. This is because objects travelling very fast will experience time dilation (1 second takes longer to tick) and so light emitted will be at a lower frequency.
Light observed from stars has traveled through incredible distances of near vacuum. The material in space absorbs some of the light, so missing or weakened bands in the spectrum give clues as to how far the light has travelled.
So... (Score:2, Funny)
Re:So... (Score:1, Redundant)
This whole article is OT (Score:3, Funny)
Why are we posting articles about Joan Rivers on
Question asked in article (Score:2, Interesting)
Re:Question asked in article (Score:3)
Re:Question asked in article (Score:1)
1 - how long does it take for the fusion to produce large amounts of heavier elements? seconds? years? millions of years? billions of years?
2 - do we have any possible explanations for having extremes but no in-between level of heavy elements?
Re:Question asked in article (Score:2)
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?
Re:Question asked in article (Score:1)
Mother in Law (Score:2, Funny)