About 4.6 billion years ago, our solar system looked nothing like it does today. Instead of a sun surrounded by planets, it began as an enormous cloud of gas and dust.
Over several million years, this cloud collapsed and flattened into a spinning disk, eventually giving rise to the sun, Earth and the other planets.
Scientists have long thought gravity was the main force driving this transformation. But new research from MIT suggests another force was also important: magnetism.
Researchers have found evidence of an ancient magnetic field preserved inside some of the oldest known material from the solar system.
The evidence comes from microscopic grains inside a remarkably well-preserved meteorite found in Antarctica in 2008.
Some of these grains, known as calcium-aluminum-rich inclusions, or CAIs, formed within the first 200,000 years of the solar system’s history. That makes them among the oldest solid materials scientists can study from our cosmic neighborhood.
The researchers estimate that the magnetic field surrounding these grains was about 150 to 600 microteslas—roughly three to 12 times stronger than Earth’s magnetic field today. Their findings were published in the Proceedings of the National Academy of Sciences.
“This transition, from a spherical cloud to a protoplanetary disk, is one of the most significant events in all of solar system history,” said MIT professor Benjamin Weiss. While gravity has long been considered responsible, he said the new measurements show magnetism probably contributed as well.
Magnetic fields can form when electrically charged particles move. In the young solar system, the collapsing and spinning cloud of gas and dust may have created a plasma filled with charged particles. Their movement could have generated a powerful magnetic field throughout the developing disk.
That field may then have helped move gas and other material toward the center, where the young sun was forming.
Scientists can investigate this ancient magnetism because tiny magnetic minerals can act like miniature time capsules. When these minerals formed, they could have aligned with the surrounding magnetic field and preserved a record of its strength for billions of years.
The team searched for this record in a meteorite called DOM 08006, discovered in Antarctica’s Dominion Range. It is considered one of the most primitive meteorites ever found because it has undergone unusually little alteration during its 4.5-billion-year history.
Researchers carefully isolated tiny grains from the meteorite and identified several ancient CAIs containing magnetic minerals, including iron. Laboratory tests revealed traces of the magnetic field that existed when the grains formed.
Previous research had already found evidence for magnetic fields about 2 million years after the solar system began, when the sun had formed and planets were starting to develop. The new discovery pushes evidence of magnetism much further back, to a time when the sun itself was still coming together.
The findings don’t mean gravity was unimportant. Instead, they suggest that gravity and magnetism may have worked together to transform a chaotic cloud of cosmic material into the organized solar system we see today.
“If you want to fully understand how the sun and planets formed,” said study leader Cauê Borlina, “you should include magnetic fields in the ingredients that make them.”
