(ORDO NEWS) — About 5 billion years ago, our region of the galaxy was a nebula composed of hydrogen gas and some dust. This was the beginning of what would become our solar system.
Somehow, part of this molecular cloud began to pile up on itself. Perhaps a passing star sent shockwaves and ripples through the dust and caused it to shrink.
Or maybe a nearby supernova did. Whatever happened, it started the process of the birth of a protostar, which eventually became the Sun.
During its birth, the Sun went through the so-called Tauri phase. It threw extremely hot winds into space filled with protons and neutral helium atoms. At the same time, some of the matter continued to fall onto the star.
While all this was happening, the cloud was in motion and flattened like a pancake. Think of it as an accretion disk feeding material into the center where the star formed. It was filled not only with the seeds of the planets, but also with a magnetic field. Planets formed in this active disk.
At first, they were clods of dust that stuck to each other and turned into stones the size of pebbles. These rocks collided with each other, forming larger and larger clusters called planetesimals.
Those, in turn, collide and form planets. This is a brief overview of the formation of the solar system. But to get more detailed information, scientists have to dig deeper.
What happened to the rest of the nebula after the planets were born? In 2017, planetary scientist Huapei Wang and co-authors reported on their research on meteorites dating back to that time.
They found that the solar nebula cleared up about four million years after the formation of the solar system.
Rocks formed in the nebula must have a magnetic imprint reflecting the magnetic fields of the time. Those rocks that formed after the dissipation of the nebula cannot boast of a large (or any) magnetic imprint. They capture the magnetism (or lack thereof) of that time and place.
A team of scientists studied meteorites found in Antarctica in late 1977/78 and in 2008. These rocks are made up of a primordial material called “carbonaceous chondrite” that formed early in the history of the solar system.
The team focused on magnetite (an iron oxide mineral) found in each sample. Magnetite “records” the so-called “residual magnetization” caused by the presence of a local field.
They then made comparisons with other paleomagnetic studies of some rocks called “angrites” that were not magnetized. Presumably, they formed after the solar nebula (and its inherent magnetic fields) dissipated.
Further analysis made it possible to determine the time frame for the cleansing of the inner and outer solar systems. For the inner region, the team found that the dissipation of the nebula occurred about 3.7 million years after the formation of the solar system. The outer one took another 1.5 million years.
The idea of using rocks to date the solar nebula and its scattering has implications for protoplanetary disks around other stars. She suggests that most of these disks go through a two-scale evolution.
Combined with previous work showing that protoplanetary disks have substructures, we gain a greater understanding of the chaotic conditions shortly after the birth of our sun and planets.
Contact us: [email protected]