As I understand it, stars like our sun were formed from the debris of previous stars, which exploded. These exploding stars (novas) ejected their constituent materials at high velocity-particles from early stars are still moving very fast.
Then, in the massive clouds of gas and debris, a process of agglomeration happened-gravitational attraction caused this materail to attract eachother. Eventually, enough mass was collected to form as a second generation star-as soon as the core of this star got hot and dense enough, fusion began, and the star began to radiate light.
My question: aren’t the odds incredibly slim that this would happen? Space is mostly…empty space. plus, the exploded star remnants are travelling away from eachother, at incredible speed-what would cause them to link together?
Are second generation stars incredibly rare?
I’m not quite clear on the question you are trying to ask, and I’m frankly not certain that you are, either. Perhaps a brief explanation of how stars are classified will help.
It is some matter of confusion that the oldest stars are actually called Population III stars. These are virtually metal-free O-type stars (no elements heavier than lithium) formed from the initial mass of material that condensed somewhere around 400 million years after the Big Bang. Because of the low density of the stars, they tended to be very massive (hundreds of times the mass of the Sun) and burned out quickly. Population II stars, which are metal-poor, are the next classification of stars, which are also comprised of larger, faster burning stars, tending to fall into B class main sequence. These stars tend to burn longer and further along the C-N-O chain, forming heavier elements, and producing the heavy metals in supernova explosions. (While Pop III stars also experienced even larger hypernovas, the low density of the constituents and the violence of the explosion prevented significant production of heavier elements.) The detritus of these stars gives the material for Population I stars, which are the stars we see locally (in the local supercluster of galaxies) which have a wide spread of spectral types but tend to be more metal-rich than previous populations The Population, model, by the way, is not really discrete; there are obviously graduations between the different populations, and areas where metal-rich and metal-poor stars tend to form.
As for how stars form and age (known as stellar evolution), it should be understood that this doesn’t happen in a vacuum. We can really only study stellar evolution in our local neighborhood (and then, only by inference, as it occurs over millions of years) and so we don’t really know how stellar evolution functions outside of a spiral-type galaxy, but our understanding is that material condenses into a giant molecular cloud that is tens of light years across. The internal gravity of the cloud–the attraction of aggregate masses of gaseous material to itself–acts to both slow the motion of the individual particles with respect to each other and heat them by conversion of gravitational potential radiation. Eventually, enough mass nucleates around individual points to cause material to condense into accretion disks, and from thence into stars and planets.
It may help to understand that while everything in the universe has some kind of linear velocity (i.e. it wants to go in a straight line in some direction), it also has angular velocity (it wants to rotate). When two bodies with different angular velocities–be they individual particles, solid bodies, or clouds of material–interact, some of that velocity is lost or at least converted, and the two bodies tend to collapse into closer orbits about one another. When enough random interactions of this nature occur, bodies eventually fall into closed orbits and will finally collide or condense, and the more this happens, i.e. the more mass that accumulates in one place, the more it tends to happen.
Stranger
This sounds like a question I asked before…“How many Super Nova Does it take to Make a Amoeba?”
Considering Stars are more of less a few light years a part, after a supernova and the scattering of elements, wouldn’t all that matter disperse in a radius of a few light years as a few random atoms to the Mile Cubed?
Exactly how does all this tend to condense again into planets and such, over such distances, after the first few gen Stars?
How many Super Nova does it take to smash enough stoof together to make a new star system light years away, to create a new Sun and eventually, lil’ Amy Meba? :dubious:
What makes you think all the initial hydrogen went into the first stars? Since it didn’t any compression waves (say from a stellar explosion) moving through the hydrogen clouds will trigger the next round of star birth while seeding those stars with some heavier metals.
Ralph, our Sun is what’s known as a Population I star, since it was the first type discovered. But as far as we can tell, it’s a third generation star.
At the beginning (when the Universe was hot, dense, and expanding incredibly rapidly), space was almost the exact same density everywhere. A few parts were slightly more dense than others by a few parts in 100,000, while a few were cooler. But while it’s very hot, the pressure from the extraordinarily energetic radiation (photons, mostly) prevented regions with more matter/energy/gravity from attracting others and growing.
As the Universe expanded and cooled, that changed. We formed neutral atoms, the attractive gravitational effects of matter became more and more important, and the pressure from photons dropped. The denser areas got richer and richer by attracting more and more matter, and after about 50-100 million years, lots of stars formed!
The first, very massive stars likely only lived for a hundred thousand years or so, and most of them died in violent supernova explosions. But they were all found in regions much denser than “average” space. So these “enriched” gas elements that had been fused beyond hydrogen and helium were spread out among the interstellar gas and dust. This typically triggers a new wave of star formation, which we find all over our own galaxy in the form of open star clusters (like the Pleides).
The very first stars – Population III stars – are called “metal-free” stars because they only have hydrogen and helium. But once they spew the first chunks of heavier elements (carbon, oxygen, nitrogen, neon, silicon, iron, etc.) into space, the stars that form after that will all be Population II stars: metal-poor (but not metal-free) stars.
We find them mostly, today, in globular clusters, as the 13.7 billion year age of the Universe is only long enough for stars more than about 85% the mass of our Sun to have died. Less massive stars, even the ones created 13.6 billion years ago, are still chugging along, fusing their hydrogen into helium.
And where population II stars have run out of fuel, died by going supernova, and triggered new star formation (this only happens within gravitationally bound structures, like galaxies and smaller), that’s where you get a Population I star, like us. They are not incredibly rare; there are something like 10^23 of them in the Universe.
In addition to novas and supernovas there are other phenomena that generate extreme pressures but which are directional. I’d have to check but I think that applies to pulsars and magnetars as well as black holes - which tend to send intense radiation out along their axes as matter falls on the accretion disk. That would be enough to herd stray hydrogen and helium together with heavier elements into areas of significant concentration. Gravity takes over from there.