The prevailing theory has been that our solar system started when the shock wave of a nearby supernova compressed the gas and dust in our neighborhood.  NewScientist reports a new study by Martin Bizzarro of the University of Copenhagen in Denmark and colleagues is pointing toward a gentler start.  The new theory is that the wind from an extremely massive star, about 30 times the mass of our sun, is the culprit.  Supernovas create iron-60 while super massive stars create Aluminum-26.  The meteorites formed at approximately the same time as our solar system do not contain iron-60 but do contain Aluminum-26.  Meteorites from a few million years later do contain iron-60, suggesting that maybe that super massive star later exploded as a supernova.