Our solar system is strangely lacking in the isotope iron-60, which could indicate that we had an unusual origin. In fact, our solar system might belong to an exclusive club whose members include just 1 to 16 percent of all sun-like stars in the entirety of the universe, reports Phys.org.
The theory, proposed by scientists at the University of Chicago, is that our sun formed in a bubble created by the solar wind emanating from a far, far larger star — a so-called Wolf-Rayet star. Such stellar objects are 40 to 50 times the size of our own sun and are the hottest of all stars. When they blow, there are consequences. And among those consequences, is us.
When a Wolf-Rayet star sheds its mass, a stellar wind blows fiercely through the material that was around it, and this forms a bubble structure with a dense shell. Because of this protective layer, the space inside the shell becomes a good place for stars to form. It's kind of like a giant egg, and inside there's a nursery.
The principal clue that suggests our solar system might have developed within one of these nurseries is the curious balance of two key elements, aluminium-26 and iron-60. Studies of meteorites left over from the early solar system suggest that we have lots of the former, but little of the latter. This balance is consistent with what happens inside the shell of a Wolf-Rayet star bubble, but it's inconsistent with what we see in the greater universe itself.
"The idea is that aluminum-26 flung from the Wolf-Rayet star is carried outwards on grains of dust formed around the star. These grains have enough momentum to punch through one side of the shell, where they are mostly destroyed—trapping the aluminum inside the shell," explained Vikram Dwarkadas, coauthor on the study.
Our solar system, according to the new research, would have formed when part of the shell collapsed inward due to gravity.
But if our solar system formed in such a way, what happened to the Wolf-Rayet star that birthed us? Here's the kicker: it likely collapsed into a black hole. A direct collapse to a black hole produces little iron-60.
The theory is mostly speculation at this point, and more research will be needed to truly narrow down the reasons why iron-60 might be scant in our solar system, but it certainly paints a compelling picture.
The research was published in the Astrophysical Journal.