There was a suggestion that the Sun was born in the cluster M67, a particularly old and persistent cluster about the same age as the Sun. But this cluster is now believed to be about half a billion years too young to be the Sun’s birth cluster.
Most clusters from that era disappeared long ago, so we will probably never know exactly where it was, how big it was and how many stars died to form it.
I’m used to the idea that stars are at least 3-5 light years apart, so were stars closer together in the past? Or is a distance like that enough to form one giant molecular cloud? If the sun along with our nearby stars all went nova tomorrow, would they form one giant gas cloud or are they too far apart for that?
To be fair, the significant majority of the Solar System’s mass is hydrogen, which is essentially all primordial, and of what’s left, most is helium, some of which is also primordial. So it is fair to say that most of the mass of the Solar System is stuff that came from the Big Bang.
Now, Earth specifically is mostly made up of heavier stuff, almost all of which had to come from the corpses of previous generations of stars. But we’re just an afterthought as far as the System as a whole goes.
Do we know what percent? My understanding is when the solar system formed, the heavier elements moved closer to the center and planets like Mercury, Venus, Earth & Mars have more heavier elements.
If that is true (and I don’t know if it is), why didn’t the sun absorb most of the heavy elements? Or did it and they are at its core?
Also do we know what % of the solar system’s mass is made of hydrogen and helium that came from the big bang and has not undergone any atomic changes? Is it 90%, 99%, 99.999%?
Wiki has a numerical breakdown of estimated relative abundance in the Galaxy, and a graph for the Solar System which appears basically similar. There’s about ten times as much hydrogen as helium by mass, and about a hundred times more helium than oxygen, the next-most-abundant. The biggest difference between the Solar System figures and those for the Galaxy is that the H/He ratio appears to be significantly higher for the Solar System than for the Galaxy as a whole: I’m unsure why this would be.
I’m also having a hard time pinning down the fraction of He that’s primordial, beyond a vague “most of it”. But it looks like big bang nucleosynthesis models generally predict a primordial composition of about 25% He to 75% H, which is very close to the ratio measured for the Galaxy. Allowing for error bars on both figures, it’s probably reasonable to say that 90-something percent of He is primordial. Assuming that the Solar System’s helium has the same ratio as the rest of the Galaxy (that is, that whatever process decreased our relative abundance of helium did so equally to primordial and stellar-generated helium), that would mean that roughly 1% of the Solar System’s mass is in non-primordial material.
You seem to be suffering from a mistaken idea of how new stars are formed.
Stars are not just formed anywhere in the galaxy. They’re mainly formed in the spiral arms, which are density waves in the gas and dust. What density waves mean is that the gas and dust is continually moving through the area, but it slows down when passing through the density wave and then speeds up again when it leaves. So while the gas is in these density waves, it forms relatively dense clouds that sometimes collapse to form new stars. (I say stars, plural, because these clouds usually fragment to form many stars.)
A nearby supernova may trigger the collapse, but the stuff coming from that supernova is only a very small part of what forms the new stars and planets. Most of it is stuff that’s been in the interstellar medium (which is what astronomers call the gas and dust between the stars) for ages. Note that the supernova will not be in the middle of the cloud, but rather some distance away, say a dozen or so light years.
If it means anything, during the one astrophysics class I took in school, the prof was insistent that all of the stars in the entire universe for all of history haven’t produced enough Helium to make a noticeable correction on the primordial abundance universe-wide, and that folks doing that kind of survey just assume it’s 100% primordial.
Nice timing. Todays APOD is Where Your Elements Came From.Explanation: The hydrogen in your body, present in every molecule of water, came from the Big Bang. There are no other appreciable sources of hydrogen in the universe. The carbon in your body was made by nuclear fusion in the interior of stars, as was the oxygen. Much of the iron in your body was made during supernovas of stars that occurred long ago and far away. The gold in your jewelry was likely made from neutron stars during collisions that may have been visible as short-duration gamma-ray bursts. Elements like phosphorus and copper are present in our bodies in only small amounts but are essential to the functioning of all known life. The featured periodic table is color coded to indicate humanity’s best guess as to the nuclear origin of all known elements. The sites of nuclear creation of some elements, such as copper, are not really well known and are continuing topics of observational and computational research.
