# Solar System formation, considering its and the universe's age

It is known that the Sun is 4.6 billion years old, and the complete Solar System is of a similar age. The class of stars to which the Sun belongs seems to be quite common. Stars of its class can live for 8 or 9 billion years before moving to the red giant stage. Also, the whole universe is less than 14 billion years old.

Thus, not many generations of Sun-like stars could have existed before the first stages of our Solar System. And heavy elements are created when stars collapse. While there could be a lot of star classes with much shorter lifespans, I'm wondering: where do the heavier elements came from? Not only for our Solar System, but many others. I think it is very likely that our Solar System is of average age; do the numbers match between dead stars and remote stellar systems? Are there studies about this?

• The distribution of star classes is not believed to be linear over time. Stars similar to the Sun are unlikely to have been so common during the early evolution of the universe. Dec 15, 2014 at 17:56
• I thought this same thing a couple of years ago. My research led me to understand that earlier in the universe's history the stars were larger and much shorter lived. I never was able to find a nice 'timeline' showing how we could get to the level of heavy elements seen throughout the solar system though so I hope someone here can provide some references to that sort of data. Dec 15, 2014 at 18:22

I think the key to this is that most of the heavy elements in the gas in our Galaxy come from stars more massive than the Sun, and which have much shorter lifetimes as a result. [Stellar lifetime is roughly proportional to $M^{-2.5}$]. So several "generations" of these have lived and died (and must have done so).
To add some more detail. Almost all the elements heavier than Helium (known as "metals") are produced inside stars. To get back into the ISM you have to get the "processed" material out of the centres of the stars. This occurs in basically three ways. (i) Supernovae - the explosions associated with the final collapse of very massive stars ($>10 M_{\odot}$). The supernova progenitors have short lives $<50$ million years, so many generations of such stars can have lived and died before the Sun was formed, and probably of order a few hundred million to a billion had done so. (ii) Giant star winds. These occur towards the ends of the lives of stars with mass of $<10M_{\odot}$. Some fraction of processed material gets dredged out of the centre and expelled into the ISM. The lifetimes of these stars is 50 million to $>10$ billion years. Most of the enrichment is caused by stars about in the middle of this range. These stars go on to fade as white dwarfs. (iii) Type Ia supernovae. Explosions triggered by mass transfer on to a white dwarf (probably in binary systems) causing a detonation and the scattering of metals into the ISM. Progenitors have lifetimes similar to the giant stars in (ii).