The story of our planetary systems origin is pretty popular. It goes like this: the Sun began as a protostar in its “solar nebula” over 4.5 billion years ago. Over the course of a number of million years, the planets emerged from this nebula and it dissipated away. Obviously, the devil is in the information. For instance, exactly the length of time did the protoplanetary disk that brought to life the planets last? A current paper submitted to the Journal of Geophysical Research takes a more detailed take a look at the planetary birth crèche. In particular, it demonstrates how the magnetism of meteorites helps inform the story.
About That Solar Nebula
Some 5 billion years back, our area of the galaxy was a nebula made of hydrogen gas and some dust. That offered the seeds of what became our solar system. Whatever took place, it started the birth process of the protostar which ultimately ended up being the Sun.
Artists impression of the solar nebula. As soon as existed in this cloud to comprehend conditions at that time, astronomers study the leftovers of solar system formation that. They wish to know the length of time it lasted after the development of the solar system. Image credit: NASA
During its birth process, the infant Sun in its birth crêche went through whats called the T Tauri phase. It blew very hot winds filled with protons and neutral helium atoms out to area. At the same time, a few of the material was still falling onto the star.
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Not only was it filled with the seeds of worlds, however it was also threaded with a magnetic field. Those, in turn, clash and form planets. Thats the executive summary of solar system formation.
Studying Rocks from the Solar Nebula
Once the worlds were born, what occurred to the remainder of the nebula? In 2017, planetary scientist Huapei Wang and collaborators reported on their studies of meteorites dating back to that time. They discovered that the solar nebula had cleared by about 4 million years after solar system formation.
To answer that, the team turned to a characteristic called “solar nebula paleomagnetism”. Meteoroids formed in the nebula at that time (called carbonaceous chondrites) include imprints of that field. Borlina and the group hypothesized that there was one schedule for the inner solar system and one for the outer areas.
The rocks that formed in the nebula ought to reveal a magnetic imprint reflecting the magnetic fields at the time. Those formed after the nebula cleared wouldnt reveal much (or any) magnetic fingerprint. They would tape-record the magnetism (or absence of it) of that time and place.
Magnetism in Primordial Rocks
Borlinas team studied meteorites discovered in Antarctica in late 1977/78 and 2008. Those rocks are made of a primordial product called “carbonaceous chondrite” that formed early in solar system history. The group focused on magnetite (an iron oxide mineral) found in each sample. Magnetite “records” whats called “remanent magnetization” enforced by the existence of the regional field. Then, they compared to other paleomagnetic studies of particular rocks called “angrites” that were not allured. Most likely, these formed after the solar nebula (and its intrinsic magnetic fields) had dissipated.
The additional analysis provided a time frame for clearing the inner and external solar system. For the inner area– 1-3 AU, from roughly the orbit of Earth to the external limitation of the Asteroid Belt– the team discovered the nebula dissipation happened about 3.7 million years after the development of the planetary system. The outer solar system took another 1.5 million years to clear.
That squares with the earlier quote of around 4 million years for the total sweep. That will let them figure out precisely when the rocks acquired the imprints of magnetic fields.
Implications for Other Solar Systems
The idea of using rocks to “date” the solar nebula and its dissipation has implications for protoplanetary disks around other stars. It recommends that the majority of such disks go through a two-timescale development. Couple that with earlier work revealing that protoplanetary disks have foundations, and we now have more insight into the chaotic conditions quickly after the birth of our Sun and planets.
For more details
Life time of the Outer Solar System Nebula From Carbonaceous Chondrites
Paleomagnetic Evidence for A Disk Substructure in the Early Solar SystemLifetime of the Solar Nebula Constrained by Meteorite Paleomagnetism
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It goes like this: the Sun began as a protostar in its “solar nebula” over 4.5 billion years earlier. They discovered that the solar nebula had cleared by about 4 million years after solar system development.
Probably, these formed after the solar nebula (and its intrinsic magnetic fields) had dissipated.
For the inner region– 1-3 AU, from approximately the orbit of Earth to the external limit of the Asteroid Belt– the group found the nebula dissipation happened about 3.7 million years after the formation of the solar system. The idea of using rocks to “date” the solar nebula and its dissipation has ramifications for protoplanetary disks around other stars.
