A massive hole on the Sun's surface has released a record amount of rare helium-3 gas into space. In October 2023, this gas, emitted from a solar jet, was measured at 180,000 times the normal concentration. This discovery opens new doors to understanding the Sun's mysteries.
In late October 2023, an unprecedented release of helium-3 was recorded from the Sun—marking the highest level of this isotope ever observed from our central star. Astronomers traced the source to a solar jet emanating from the edge of a coronal hole, part of a rare solar flare that only contained light elements.
According to astrophysicist Radoslav Bučík from the Southwest Research Institute in the U.S., helium-3 is a rare isotope that's one neutron lighter than the more common helium-4, with only one helium-3 ion for every 2,500 helium-4 ions. He explains that solar jets appear to preferentially accelerate helium-3 due to its unique charge-to-mass ratio.
Helium-4 is the most common helium isotope, making up about a quarter of all normal matter in the Universe. Both helium-3 and helium-4 likely formed just after the Big Bang, but helium-3 remains much rarer.
In the solar wind, helium-3 typically makes up only about 0.002% of the particles. But solar jets can increase that concentration by about 10,000 times. On October 24–25, 2023, ESA and NASA's Solar Orbiter detected levels 180,000 times higher than normal, with helium-3 accelerating away from the Sun at unusually high speeds.
At the time, solar observatories spotted a large coronal hole on the Sun's surface. These holes are temporary regions in the Sun's atmosphere where magnetic field lines open up, allowing solar wind to escape more freely. They appear dark in UV and X-ray images due to being cooler and less dense.
In this case, the researchers identified a highly focused stream of plasma—a solar jet—as the source of the helium-3-rich particle event. Surprisingly, the magnetic field in this region was weak, more typical of quiet solar zones, supporting theories that helium-3 enrichment occurs more easily in low-turbulence, weakly magnetized plasma.
What made this jet even more interesting was its particle composition. Solar particle events usually contain helium-3 along with high concentrations of heavier elements like iron. However, the October 2023 event lacked elevated iron levels, instead being rich in lighter elements such as carbon, nitrogen, silicon, and sulfur.
Only 19 other events with similar chemical profiles have been recorded between 1999 and 2023. This rarity could mean such events are either uncommon or simply too faint to detect from Earth. Positioned between Earth and the Sun, the Solar Orbiter is well-suited to capture the Sun's diverse and mysterious outbursts.
