>>2,3
Just the solar system, not the whole galaxy.
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Anonymous2009-02-09 4:20
Awwwhhh shit.
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Anonymous2009-02-09 8:49
so the galaxies that were created first completely lack gold and other stuff created in supernovas?
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Anonymous2009-02-09 14:06
Gold comes from supernovas?
Is this science?
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Anonymous2009-02-09 16:04
Matter comes from stars as tiny particles and gasses. This matter consists of most elements on the periodic table. Eventually this matter gathers its mass together by the force of gravity and forms a planet. So all natural elements found on Earth come from the stars. But it sounds stupid if you explain "matter came from stars" to anyone, just as if you said "God created matter," so it isn't taught very often.
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Anonymous2009-02-10 8:13
I'll try to explain it as briefly as I can, but please realize that I'm oversimplifying it quite a bit.
It started, of course, with the Big Bang. Now, the infamous "Big Bang Theory", as it is somewhat inaccurately known to laymen, only attempts to explain what happened immediately AFTER the event in question. Our current mathematical models can only reliably explain what happened back to about one hundred billionths of a second (1 x 10^-11 seconds, 1/100,000,000,000 seconds) after the event. Before that point, most models start to give meaningless answers, because of the extremes involved.
Some models show that at about 1 x 10^-37 seconds after the Big Bang, the Universe was filled pretty homogeneously with a type of high energy plasma. This plasma, called a quark-gluon plasma, consisted of free quarks and gluons, which are the building blocks of protons and such. At about 1 x 10^-6 seconds after the Big Bang, the plasma had expanded and cooled enough to allow the quarks and gluons to form baryons (protons, etc).
At about 1 second after the Big Bang, the temperature was already "only" about 1 x 10^9 K (a billion degrees Kelvin, 1.8 billion degrees F), which was cool enough (yet hot enough) for a process called Big Bang (or "primordial") nucleosynthesis to occur. This basically means that the free protons and neutrons were able to fuse into the atomic nuclei. Most remained single protons, but some became deuterium or helium, and rarely lithium and a few others.
It took another 379,000 years of expansion and cooling before the free electrons were able to pair with the free protons and nuclei to form atoms. About 75% of the atoms were Hydrogen, about 25% were Helium, and everything else was only present in trace amounts. (Even today, the Universe is about 74% Hydrogen, 24% Helium.) Atoms aren't able to absorb nearly as much energy as free particles and the extra became what is known as the cosmic microwave background radiation.
Due to gravity, slight differences in density began to form large gas (well, still technically plasma), which then formed quasars and stars. These first stars started showing up after about 150 million years. A star is basically just a cloud of mostly hydrogen and helium that became so dense that the temperature rose enough to start a fusion reaction. The Hydrogen and Helium atoms fuse together into heavier elements, which are fused again and again.
All of the heavy elements (again, basically everything besides Hydrogen, Helium and a few traces of other things) were created in stars. Most of the material is ejected into space in supernovae, which then eventually mixes in with other gas clouds. Those clouds then form solar systems, with most of the lighter elements being pulled "quickly" into the the center to become the star and the heavier elements clumping together a bit slower to form planets.
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Anonymous2009-02-10 8:20
>>10
LOL, I didn't realize how long that got. My bad.
tl;dr version:
When a supernova ejects the heavy elements into space, they mix with other gas clouds. The light elements (Hydrogen and Helium, for the most part) clump much more quickly, forming the new stars, while the heavier elements clump slower, forming the planets.
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Anonymous2009-02-10 11:29
>>10
>Even today, the Universe is about 74% Hydrogen, 24% Helium
1) Due to gravity, slight differences in density began to form large gas
Should be "large gas clouds" or "large gas nebulae". Most people probably got it from context, but just in case someone was confused.
2)
I would also add that in normal "stellar nucleosynthesis" , iron is the upper limit for fusion. Heavier atoms aren't able to be produced produced until the star goes supernova, during "supernova nucleosynthesis". Also, a supernova is basically a gravitational collapse followed by a ridiculously powerful explosion.
But yeah, it's hard not to go into too much detail when you're trying to explain complicated Science topics. Scientific Knowledge is fractal, you can always go a bit more in depth to present a more accurate picture, but it requires an exponentially growing amount of background information. Plus, it's always growing, continually being updated and improved.
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Anonymous2009-02-20 16:29
>>19
>ridiculously powerful explosion
should i be ridiculing it?
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Planetary Sci-guy2009-02-20 21:49
approximately 4.5-5 billion years ago, a supernova event occurred in close proximity to the gas cloud our solar system would eventually coalesce from. Essentially, a massive star ran out of fuel (elements lighter than iron) in its core and could no longer generate radiation pressure in sufficient opposition to self gravity to maintain hydrostatic equilibrium. in the process of collapse, material falling into the core (at great speed) "bounces" of the super dense core, and under these extreme pressures fuses into the various elements heavier than iron, including gold.
These heavier elements are ejected from the supernova in relatively spherical shells that expand radially from the died star. As this material (in a vapor state) cools, it begins to condense. metals being the first to condense into a solid (including gold), then silicates around these metal cores and finally volatiles. At this point they are just football-shaped differentiated dust grains on the order of half a micron in size or so, and are moving far to quickly away from the supernova to really form anything, as they become more diffuse the further they spread out.
Now that gas cloud comes into play. the gas drags on the dust, slowing it down, while the dust, being just the right size, is able to cool the gas by blocking cosmic radiation (wavelength smaller than the dust grains), yet allowing thermal radiation to escape. Saying the gas cools is equivalent to saying the average kinetic energy of each gas molecule is decreased, and at some point the gas is moving slow enough that self gravity dominates over gas pressure, allowing nebular collapses into protoplanetary disks. Conserving the overall angular momentum of the gas cloud, dust and gas orbit around a common center of gravity, and through various collisional interactions circularize their orbits into a disk, at the center of which forms the proto-sun. heat from gravitational collapse, begins to vaporize the dust near the center of this disk, preferentially expelling volatiles, and allowing metal-silicate bodies to accrete (first through sticky collisions between particles, then static cling as complex particles become larger and polarized, and at some stage, gravity dominates. regardless, they start to clump together into large bodies.)
Eventually, planetary embryos are formed, and collide, forming the terrestrial planets we see today. heat from accretion and radioactive decay (more radioactive isotopes to fizzle so quickly after nova fusion) allow these bodies to gradually differentiate; that is to say that heavier (denser) material melts and sinks toward the center of gravity (why we have a dense metal core), and lighter materials rise to the surface. this process isn't perfect however, and heavier elements (like gold) can remain at any depth in the planet, albeit in small proportions as trace elements, general a few parts per billion.However, Earth is geologically active. surface and mantle rocks are continuously being melted and allowed to solidify. Liquid water flows on the surface an permeates the crust to great depths. minerals don't all melt at the same temperature, and rocks can have varying solubility in water depending on temperature and pressure. Processes such as fraction crystallization, can preferentially enrich magmas in trace elements, simply by crystallizing and removing major elements and minerals until these trace minerals are all thats left. If left to crystallize they can be brought to the surface by tectonic processes, or dissolved by geothermaly heated water and again be brought to the surface to precipitate out. where they can be mined as ore, dissolved in acid, and have they're precious content extracted, melted down, purified, molded, and surgically implanted into the mouths of people who probably ought to be investing in education rather than grills.
As for your second question, the IAU definition of a star requires that the body in question be fusing Hydrogen in its core, so no, the earth is not a star. however it is made from the debris from a star.
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Anonymous2009-02-21 10:45
All the elements in the stars are found on earth, because in short, we are made from them.
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Anonymous2009-02-21 16:33
radioactive decay and preferential differentiation of the protoplanetary disk would suggest otherwise.
but yes, we are all made of star stuff.
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Anonymous2009-02-23 11:27
But it sounds silly
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Anonymous2009-02-27 22:50
>>24
Why? Because you don't know shit about physics or astronomy?
SYDNEY - Australian researchers have found minuscule nuggets of gold hidden inside the leaves of eucalyptus trees in a discovery they say could help prospectors discover new deposits of the precious metal.