When you picture a celestial world surrounded by rings, Saturn is probably the first thing that pops into your head. But scientists have long suspected that the Sun might contain rings of dust hidden in its atmosphere, along with other mind-boggling phenomena such as plasma “blobs” and “magnetic islands.”
These weird solar features are described in one of four new papers published in Nature on Wednesday, based on dispatches from a record-breaking NASA spacecraft called the Parker Solar Probe.
During two recent encounters in October 2018 and April 2019, Parker traveled closer to the Sun than any other mission. The results from its daring dives have provided an entirely new view of our star.
“We’re really getting into the atmosphere of the Sun and we’re unfolding the global magnetic field of the Sun, which we have not seen in detail,” said Angelos Vourlidas, a co-author of the new study and an astrophysicist at Johns Hopkins University, in a call.
“It’s like lifting a blanket and seeing what’s under it,” he added.
Vourlidas and his colleagues were hoping that Parker could catch a glimpse of the “long-sought dust free zone” in the Sun’s atmosphere, as it is described in their paper. This zone, if it exists, could mark the outer edge of a hypothetical pattern of rippled rings that are made of dust with various compositions and weights, such as iron or silicates, and separated by dust-free gaps.
For nearly a century, scientists have theorized that this zone might exist based on observations and models. The composition and patterns of dust within and around the Sun can help reconstruct the “dust history” of the solar system, Vourlidas said, which contains valuable information about the evolution of planets and other celestial objects around our star.
Knowing whether there are dust-free or dust-light zones inside the Sun, separated by rings, also has the potential to help scientists make predictions about the habitability of alien star systems.
“Understanding what type of dust survives closer to the star, versus what is a little farther away, could maybe help physicists come up with better theories to pinpoint which stars are more likely to get rocky planets compared to say, gaseous planets like Jupiter,” Vourlidas said.
It is challenging to observe such fine details of the Sun without getting a closer look, which is where Parker Solar Probe fits into the story. During its first closest encounters with the Sun, called perihelions, the probe traveled to within 15 million miles of the solar surface, far closer than any mission before it.
From that vantagepoint, Vourlidas and his colleagues used Parker’s Widefield Imager for Solar Probe (WISPR) instrument to take pictures of this unexplored region. The team was surprised to find “tantalizing evidence” of the dust-free zone, Vourlidas said.
“Even with these first two orbits that we have analyzed, when we look at the very edge of our instrument, toward the Sun, we start seeing the intensity of the dust is a bit lower than you would expect from what we have been observing from Earth,” he explained.
He cautioned that this is not full confirmation of the existence of dust rings, just yet. “It’s looking like the dust is falling away, as you go closer,” he said. “We’re really looking forward to the next perihelion in January where we will be 20 percent closer to the Sun so that we will be able to see if that trend continues.”
In addition to probing a potential ring system within the Sun's atmosphere, Vourlidas and his colleagues were able to capture evidence of mysterious small-scale solar activities, including small amounts of plasma that the Sun shoots out as “blobs,” the study said.
Parker also saw large oblong structures that hint at the potential existence of “magnetic islands.” These islands are elliptical crossings of magnetic field lines that appear in models of the Sun. Though they may be only particle-sized when they form, the islands may play a role in the most dangerous eruptions from our star, known as coronal mass ejections (CMEs).
“The simulations show that [the islands] mess with each other and form bigger and bigger coils,” Vourlidas said. “Maybe, then, that’s how CMEs eventually form, in a fractal type of process that starts on a small scale and ends up with something huge.”
It will take more observations and simulations to figure out if the large oblong structures observed by Parker originated from magnetic islands.
Vourlidas is also optimistic that the probe might bear witness to a comet being devoured by the Sun during its future close encounters.
“That’s what I’m hoping to see—a comet in our pictures that comes in and basically breaks apart—as long as it is far away from us,” he said. “If it is too close and we go through the dust, we’re going to get sandblasted. That’s not good. I want it to be far away.”
“But it would be quite an amazing picture because we would be able to see the dust twinkling,” he added.
Parker will eventually travel to about 3.83 million miles from the Sun’s surface, more than three times closer than these recent encounters, in 2024. Given how much it has already learned from a much greater distance, there are sure to be more discoveries on the way.