Key takeaways

  • Tiny crystals in meteorites show the Sun was much more active billions of years ago.
  • Early Sun emitted powerful particles that affected objects without magnetic protection.
  • These ancient crystals in the Murchison meteorite contain helium and neon from solar particles.
  • Helium and neon in the crystals indicate high-energy impacts from the young Sun.
  • The Sun’s activity dropped, changing the irradiation conditions in the early solar system.

Tiny crystals in meteorites bore evidence to the Sun’s erratic behavior in its early years.

The Sun delivers more than just sunshine and rainbows our way. Our star emits high-energy particles capable of interacting with atom nuclei on a regular basis. The Earth’s magnetic fields protect us from many of the negative impacts of this powerful particle shower, but not every object in the solar system is as safe.

Researchers discovered that the Sun was significantly more active during the early years of the solar system, before Earth existed. Scientists looked into microscopic crystals called hibonites from the Murchison meteorite, which crashed to Earth in 1969. These crystals were most likely among the first minerals to form in the solar system, appearing before Earth some 4.5 billion years ago. Scientists discovered that the hibonite crystals included a high concentration of helium and neon atoms as a result of bombardment by tons of powerful particles from a young Sun. The findings were published in Nature Astronomy.

Ancient Crystals

Astronomers have discovered that young stars are more active and emit more high-energy particles than older stars. To determine whether the Sun experienced an active phase like this, scientists have been investigating the chemical makeup of meteorites for telltale indicators of reactions produced by energetic particles. They have previously discovered evidence that the Sun was active in its early phase from other known elements in meteorites, but these helium and neon measurements in hibonite crystals are the most conclusive yet.

“What came together here was that we looked at samples that are probably the oldest or among the oldest materials that we have access to from a meteorite, because it was important to look at very old materials, and then we looked at helium and neon,” according to Levke Kööp, the first author of this discovery.

The crystals contained helium and neon atoms, which were the giveaway. Helium and neon are noble gases, which seldom form chemical bonds and would not have linked to the hibonite crystals as they formed. So, how did these noble gases get there?

Hibonite crystals consist of numerous elements, including calcium and aluminum. When high-energy particles from the Sun strike some of these atoms, they can split into smaller atoms such as helium and neon. Kööp and her colleagues believe that, because these noble gases could not have linked with the crystals as they formed, the helium and neon atoms seen in hibonite crystals must be the result of this splitting produced by high energy particles.

The researchers discovered that other meteorite grains did not exhibit the same level of particle radiation effects. This implies that much of the energetic particle bombardment that affected the hibonite crystals occurred very early in the solar system’s history, when the crystals were still young and had not yet been incorporated into larger rocky bodies that would eventually fall to Earth as meteorites.

Something changed

When the old hibonite crystals were compared to crystals made later in the solar system’s history, it was discovered that the Sun was quite active early in its life, but something changed abruptly in the early solar system, causing subsequent crystals to receive less energetic particle radiation.

“Something changed in the irradiation condition,” Kööp explains. “For whatever reason, the hibonites were irradiated whereas the later produced materials were not. We don’t know why that is.

According to Kööp, it might have been a change in the characteristics of the early Solar System’s dusty disk, which would have sheltered minerals from some of the Sun’s radiation, or a shift in the amount of energetic particle radiation the Sun was releasing very early on.

The next phase, according to Kööp, would be to explore for similar helium and neon reactions in other early Solar System minerals. She also believes that this research will be valuable for simulating the evolution of the early Solar System and its dusty disk characteristics.

In any event, Kööp is pleased that the helium and neon atoms remained inside these tiny crystals for so long.

“It actually worked out so nicely, that the signature was so clear,” she tells me. “There are numerous reasons why we may not have spotted it. So it appeared like all of the stars had aligned.

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