Scientists have proposed a new method for the formation of our Solar System 4.6 billion years ago, suggesting it was born from a giant star shedding its layers rather than a supernova.
Published in the Astrophysical Journal, a study from the University of Chicago points towards a Wolf-Rayet star as the possible progenitor of our own Sun. These are some of the most massive and brightest stars in the universe.
They estimate that the particular star that led to our formation may have been 40 to 50 times the size of our Sun. As it sheds its mass, it would have formed a bubble structure around it, through which its stellar wind would travel. The shell of this bubble can be a good place to trap dust and gas, which can condense into stars.
Previously, a supernova was seen as a possible candidate for the formation of our Solar System. After a star exploded, the resulting dust and gas would have collapsed to form our protostar, which eventually would have evolved into our Sun.
However, this theory does not account for an unusual finding in the early Solar System. It’s thought there was an abundance of the isotope aluminium-26, but not very much iron-60. This is consistent with Wolf-Rayet stars, which release a lot of the former but not much of the latter.
“The fact that Wolf-Rayet winds may be responsible for the Aluminium-26 in the early solar system has been mentioned before,” Vikram Dwarkadas, a co-author of the study, told IFLScience.
“However, the assertion that the Solar System may have formed due to triggered star formation in the dense shell of a Wolf-Rayet bubble, and a complete theory to describe the entire process by which this may happen, has to my knowledge never been stated in the literature.”
Aluminium-26 would have been carried far from the star on grains of dust formed around it. These would have enough momentum to punch through the shell, where they would be destroyed – trapping aluminum in the shell. When this collapsed due to gravity, it would have led to the formation of our Solar System.
The Wolf-Rayet star in our Sun’s case would have ended its life long ago, possibly exploding as a supernova or collapsing into a black hole. But it provides an intriguing new theory to how our Solar System began, and perhaps points at ways other systems might form. About 1 to 16 percent of other Sun-like stars may have formed in a similar way.
“There is at least one specific case where star formation has been observed in the bubble of a Wolf-Rayet star so there is no doubt that this happens,” said Dwarkadas.