The shape of the solar system used to be a bit rounder.
Before the solar system flattened into a disk, its dust and rock distribution resembled a doughnut more than a pancake, scientists have concluded after studying iron meteorites from the outer solar system, which they say could explain the solar system’s former ring-like structure.
This is information that will help interpret other new planetary systems and determine the order in which they come together.
The formation of a planetary system around a star begins with a molecular cloud of gas and dust drifting through space. When a part of the cloud becomes dense enough, it collapses under its own gravity and becomes the seed of a growing baby star that grows as it spins. As it spins, material from the surrounding molecular cloud is pulled into the rotating disk that feeds the protostar.
Within the disk, small clumps form, becoming the seeds of protoplanets that either grow into full planets or (much more likely) stop developing and remain as small objects such as asteroids.
We have seen these The disk orbits other stars multiple times.As the planet moves, it sucks up dust and excavates gaps.
However, iron meteorites found within our solar system tell a different side of the story.
According to a team led by planetary scientist Bidon Chan of the University of California, Los Angeles, the configuration of asteroids in the outer solar system requires that the cloud of material be doughnut-shaped, rather than a series of concentric rings in a flattened disk, suggesting that the early stages of the system’s merger are torus-shaped.
The iron meteorite in question is a chunk of rock that has traveled a long way from outside the solar system to Earth. Refractory metal Metals such as platinum and iridium are more abundant there than those found in the inner solar system, and their formation only occurs in extremely hot environments, such as near forming stars.
This is a bit of a tricky problem, because these meteorites came from the outside, not the inside, of the Solar System, meaning they must have formed closer to the Sun and migrated outward as the protoplanetary disk expanded. But modeling done by Zhang and his colleagues suggests that these iron objects could not have crossed the gap in the protoplanetary disk.
They calculate that migration could have occurred most easily if the protoplanet had a circular structure, which would have guided the metal-rich object towards the outer reaches of the forming solar system.
Later, as the disk cooled and planets began to form, the inability of rocks to move through the gaps in the disk would have acted as a very effective barrier, preventing gravity from moving the rocks back toward the Sun.
“When Jupiter formed, a physical gap probably opened up, trapping the iridium and platinum metals in the outer disk and preventing them from falling into the Sun.” Zhang says.
“These metals were later incorporated into asteroids that formed in the outer disk. This explains why meteorites that formed in the outer disk (carbonaceous chondrites and carbonaceous-iron meteorites) have much higher iridium and platinum contents than meteorites that formed in the inner disk.”
It’s amazing what you can learn from a chunk of metal rock with a hole in it.
This study Proceedings of the National Academy of Sciences.