Triggered Star Formation inside the Shell of a Wolf-Rayet Bubble as the Origin of the Solar System
Abstract
A critical constraint on solar system formation is the high {}26{Al}/27Al abundance ratio of 5× {10}-5 at the time of formation, which was about 17 times higher than the average Galactic ratio, while the 60Fe/56Fe value was about 2× {10}-8, lower than the Galactic value. This challenges the assumption that a nearby supernova (SN) was responsible for the injection of these short-lived radionuclides into the early solar system. We show that this conundrum can be resolved if the solar system was formed by a triggered star formation at the edge of a Wolf-Rayet (W-R) bubble. 26Al is produced during the evolution of the massive star, released in the wind during the W-R phase, and condenses into dust grains that are seen around W-R stars. The dust grains survive passage through the reverse shock and the low-density shocked wind, reach the dense shell swept-up by the bubble, detach from the decelerated wind, and are injected into the shell. Some portions of this shell subsequently collapse to form the dense cores that give rise to solar-type systems. The subsequent aspherical SN does not inject appreciable amounts of {}60{Fe} into the proto-solar system, thus accounting for the observed low abundance of {}60{Fe}. We discuss the details of various processes within the model and conclude that it is a viable model that can explain the initial abundances of {}26{Al} and {}60{Fe}. We estimate that 1%-16% of all Sun-like stars could have formed in such a setting of triggered star formation in the shell of a W-R bubble.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2017
- DOI:
- 10.3847/1538-4357/aa992e
- arXiv:
- arXiv:1712.10053
- Bibcode:
- 2017ApJ...851..147D
- Keywords:
-
- astrochemistry;
- meteorites;
- meteors;
- meteoroids;
- stars: massive;
- stars: solar-type;
- stars: Wolf–Rayet;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 19 pages, 6 figures. Accepted version. Final published version with proof corrections can be found on the Astrophysical Journal web page for ApJ, 2017, 851, 147