Magnetic fields in early solar system might explain rapid planet formation

Using information gathered from small pieces of rock called chondrules, taken from the Semarkona meteorite that fell to Earth in central India during the 1940s, an international team of planetary scientists has taken steps toward solving the mysteries of how the solar system formed.

Research published in the journal Science on Nov. 14 provides the most accurate recordings of chondrule magnetism and sheds light on the role magnetic fields played in the formation of young stars and planets.

ASU astrophysics professor Steve Desch, who specializes in modeling theoretical events that could have occurred in the early universe, played a key role in the research, along with scientists from the Massachusetts Institute of Technology, Harvard University, Cambridge University and the Technical University of Denmark.

“It’s really powerful to understand where we come from,” Desch said. “I think everybody wants to know where we came from and what happened before people were around to witness it.”

He said he finds chondrule magnetism fascinating, because it can give researchers insight into the solar system’s earliest history.

“We don’t have a time machine to go back and look at how our solar system formed and explain how Earth got here, but meteorites are really cool because they were there at the very birth of the solar system, and the things that happened as the planets were assembling are recorded right there in the rocks,” he said.

He said studying the magnetic properties of chondrules in meteorites provides clues about the magnetic characteristics of the pre-modern solar system.

“We have no direct evidence,” he said. “We can’t go to another solar system right now and say, ‘What’s going on here?’ We can’t go back in time and look at out own solar system.”

Desch said the magnetic records of the early solar system provided by chondrules provide one piece to a complex puzzle when it comes to writing the history of Earth’s existence.

Roger Fu, a graduate student studying planetary sciences at MIT, worked with Desch on this research and is the lead author of their recently published paper.

He said chondrule magnetism and the overall magnetism present in the developing solar system could offer an explanation for rapid planet formation.

“The question that has not yet received a proper answer is, how does the disk evolve so quickly?” Fu said. “How does the disk actually form stars and planets in only about 3 million years? Because 3 million years, in a cosmic sense, is a very short amount of time.”

He said it had been a common theory prior to his research that magnetism aided the process of consolidation in the disks, but this theory was not supported by concrete evidence of the presence of early magnetic fields until now.

How strange, that something so small could have such a large impact on the theory of solar system evolution, Fu said.

“(Chondrules) very peculiar-looking,” he said of chondrules. “They’re millimeter-sized spheres of rock that was once molten in the creation disk.”

He said the chondrules could have been the result of enormous shock waves, which compressed gasses at a rate that produced heat capable of melting dust particles in space.

The shock waves that created the dust-melting heat, he said, could have been caused by gravitational instabilities that occur when large amounts of matter are located in the same vicinity in space.

The dust-melting shock waves could also have been caused by the orbit of early planets.

“We had protoplanets orbiting the sun, and they had very irregular orbits,” he said. “At some points in their orbits, they were very fast, and that can actually create a shock wave. It’s sort of like … when you have a boat going into water, and you see bow waves.”

However, no matter the origin of the shock waves that created the magnetic chondrules, Fu said the peculiar-looking millimeter-sized spheres of rock are an important part of the solar system’s history.

“There’s evidence — or, at least, very plausible ideas — that chondrule formation was essential to making planets,” he said. “Understanding chondrule formation is also to understand the pathway on which the planets and the solar system formed.”

MIT planetary sciences professor Benjamin Weiss has worked with Fu and Desch researching chondrule magnetism. He said in an email that their research would answer the question, at least partially, of why solar systems exist.

“One of the leading hypotheses is that (planet formation) was accomplished by a strong magnetic field that existed during the first few million years of solar system formation,” he said in an email. “However, there have been no direct measurements of the existence of such fields in the terrestrial planet forming region. Our results indicate that, in fact, a strong magnetic field did exist in the early solar system and, by implication, possibly in many planet-forming regions throughout the universe.”

Reach the reporter at megannphillips@asu.edu or follow her on Twitter @megannphillips

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