For nearly five years, a Sun-observing probe has been making close approaches to the Sun, capturing close-up views of the star’s polar regions to collect clues about its magnetic activity, corona, and atmosphere. During two recent flybys, Solar Orbiter spotted tiny jets of material that appear as thin, hair-like strands brightly flashing near the Sun’s south pole, which turned out to be a surprising source of solar wind.
The European Space Agency’s (ESA) Solar Orbiter first discovered the jets flashing on the surface of the Sun in 2023. Follow-up observations have not only confirmed that the tiny jets exist, but also revealed them as the source of the two main forms of solar wind, fast and slow. Scientists have known for decades where fast solar wind comes from, but the source of slow solar wind had remained elusive until Solar Orbiter’s onboard cameras spotted more of these tiny jets. The new findings are detailed in a study published Wednesday in the journal Astronomy and Astrophysics.
The above 40-second video is sped-up footage of the new-found jets flashing briefly near the Sun’s south pole. In reality, the jets flash for around one minute, flinging charged particles at an explosive rate of around 62 miles per second (100 kilometers per second).
Solar wind is a stream of charged particles that emanate from the Sun’s corona—the outermost layer of its atmosphere—and travels through the entire solar system. Fast solar wind originates from dark patches in the Sun’s atmosphere, called coronal holes, or regions where the Sun’s magnetic field does not turn back down into the Sun but rather travels outward into the solar system, according to ESA. Charged particles use the magnetic field lines to flow away from the Sun, creating solar wind.
To figure out how these particles get launched from the Sun in the first place, the researchers behind the discovery combined Solar Orbiter’s high-resolution images with direct measurements of solar wind particles and the Sun’s magnetic field. By doing that, they were able to connect the solar wind back to the jets observed by Solar Orbiter. Surprisingly, the researchers could also trace back slow solar wind to the tiny jets. “The fact that the same underlying process drives both fast and slow solar wind comes as a surprise,” ESA wrote.
Solar Orbiter launched in February 2020, carrying its onboard telescope to just about one-quarter the distance of Earth from the Sun to provide high-resolution, close-up observations of the host star. The spacecraft performs two close approaches to the Sun each year, and the researchers behind the new study are hoping to collect more data on the tiny jets and how they launch solar wind during the probe’s next flyby.
