the solar system began to form, based on ancient meteorites, 4.5 billion years ago.
when did the solar system begin to form, based on ancient meteorites?
4.5 billion years ago
the oldest inclusions found in meteorites, thought to trace the first solid material to form in the pre-solar nebula, are 4568.2 million years old, which is one definition of the age of the solar system. studies of ancient meteorites reveal traces of stable daughter nuclei of short-lived isotopes, such as iron-60, that only form in exploding, short-lived stars. this indicates that one or more supernovae occurred near the sun while it was forming. a shock wave from a supernova may have triggered the formation of the sun by creating relatively dense regions within the cloud, causing these regions to collapse. because only massive, short-lived stars produce supernovae, the sun must have formed in a large star-forming region that produced massive stars, possibly similar to the orion nebula. studies of the structure of the kuiper belt and of anomalous materials within it suggest that the sun formed within a cluster of between 1,000 and 10,000 stars with a diameter of between 6.5 and 19.5 light years and a collective mass of . this cluster began to break apart between 135 million and 535 million years after formation. several simulations of our young sun interacting with close-passing stars over the first 100 million years of its life produce anomalous orbits observed in the outer solar system, such as detached objects.
formation and evolution of the solar system
the sun formed about 4.6 billion years ago from the collapse of part of a giant molecular cloud that consisted mostly of hydrogen and helium and that probably gave birth to many other stars. this age is estimated using computer models of stellar evolution and through nucleocosmochronology. the result is consistent with the radiometric date of the oldest solar system material, at 4.567 billion years ago. studies of ancient meteorites reveal traces of stable daughter nuclei of short-lived isotopes, such as iron-60, that form only in exploding, short-lived stars. this indicates that one or more supernovae must have occurred near the location where the sun formed. a shock wave from a nearby supernova would have triggered the formation of the sun by compressing the matter within the molecular cloud and causing certain regions to collapse under their own gravity. as one fragment of the cloud collapsed it also began to rotate because of conservation of angular momentum and heat up with the increasing pressure. much of the mass became concentrated in the center, whereas the rest flattened out into a disk that would become the planets and other solar system bodies. gravity and pressure within the core of the cloud generated a lot of heat as it accreted more matter from the surrounding disk, eventually triggering nuclear fusion.
sun