Cosmochemical evidence for astrophysical processes during the formation of our solar system

• Published in: Proceedings of the National Academy of Sciences - PNAS 2011-11, Vol.108 (48), p.19152-19158
• Main Authors: MacPherson, Glenn J, Boss, Alan
• Format: Article
• Language: English
• Subjects: Asteroids; Astronomical Phenomena; Astrophysics; Chondrites; Comets; Cosmic dust in solar system; COSMOCHEMISTRY SPECIAL FEATURE; Dust; Extraterrestrial Environment - chemistry; ionizing radiation; isotopes; mass transfer; Meteorites; Molecular clouds; Radiation; Radioisotopes - analysis; Radionuclides; Silicates; Solar ions; Solar system; Solar System - chemistry; Solar system research; Solar systems; Star formation; Stars; Stars, Celestial - chemistry; Stellar investigations; Sun; Supernova; Supernovae; temperature
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1110051108

Through the laboratory study of ancient solar system materials such as meteorites and comet dust, we can recognize evidence for the same star-formation processes in our own solar system as those that we can observe now through telescopes in nearby star-forming regions. High temperature grains formed in the innermost region of the solar system ended up much farther out in the solar system, not only the asteroid belt but even in the comet accretion region, suggesting a huge and efficient process of mass transport. Bi-polar outflows, turbulent diffusion, and marginal gravitational instability are the likely mechanisms for this transport. The presence of short-lived radionuclides in the early solar system, especially 60Fe, 26Al, and 41Ca, requires a nearby supernova shortly before our solar system was formed, suggesting that the Sun was formed in a massive star-forming region similar to Orion or Carina. Solar system formation may have been "triggered" by ionizing radiation originating from massive O and B stars at the center of an expanding HII bubble, one of which may have later provided the supernova source for the short-lived radionuclides. Alternatively, a supernova shock wave may have simultaneously triggered the collapse and injected the short-lived radionuclides. Because the Sun formed in a region where many other stars were forming more or less contemporaneously, the bi-polar outflows from all such stars enriched the local region in interstellar silicate and oxide dust. This may explain several observed anomalies in the meteorite record: a near absence of detectable (no extreme isotopic properties) presolar silicate grains and a dichotomy in the isotope record between 26Al and nucleosynthetic (nonradiogenic) anomalies.