Scientists have identified phenomena in deep space that can act as naturally occurring “space weather stations” far beyond our solar system, offering a new way to study how stellar activity could influence the habitability of planets orbiting distant stars.
In our own solar system, space weather—driven largely by the Sun—plays a major role in shaping planetary atmospheres. Solar winds and radiation can strip atmospheres over time or alter their chemical compositions, thereby affecting surface conditions.
Until now, directly observing similar processes around other stars has been extremely difficult. However, new insights into distant stellar activity could potentially change this, as researchers behind the recent work focused on phenomena associated with a variety of M dwarf stars known as complex periodic variables.
These peculiar young stars are characterized by rapid rotation, which causes “dips” in their brightness over time. However, it was unclear from past research whether these changes in the star’s luminosity were the result of starspots—the same phenomena known as “sunspots” on our own nearest star—or as a result of material surrounding these stars.
Natural Space Weather Stations
Carnegie’s Luke Bouma, the lead author of a recent study who presented the new research at a meeting of the American Astronomical Society, said that the actual cause of this dimming had long remained in question. However, the team’s work, which relied on the creation of “spectroscopic movies” of a complex periodic variable star known as TIC 141146667, allowed them to discern areas of cooler plasma being dragged by the star’s magnetic field, giving rise to a donut or “torus”-shaped plasma sheath.
Based on their observations, Bouma says the “dips” in brightness TIC 141146667 engaged in “can tell us something about the environment right above the star’s surface.”
“The blips in dimming stopped being weird little mysteries and became a space weather station,” Bouma says, noting that the torus (i.e., donut-shaped) plasma that is dragged around these stars after becoming trapped in their magnetospheres offers astronomers a unique way to observe “what’s happening to the material near these stars, including where it’s concentrated, how it’s moving, and how strongly it is influenced by the star’s magnetic field.”
Implications for Habitable Worlds
The team’s approach could help refine estimates of habitability for planets by incorporating space weather into the equation alongside factors already relied on by astronomers. With the view beyond our own atmosphere growing clearer thanks to advanced space observatories like the James Webb Space Telescope, as more advanced telescopes come online, including next-generation space observatories like the Nancy Grace Roman Space Telescope, scientists may potentially be able to apply this technique to a wider range of systems going forward.
Fundamentally, Bouma and his co-author, Moira M. Jardine, say their research offers important new insights into the role of the plasma torus that encases complex periodic variable stars.
“These data support the idea that young, rapidly-rotating M dwarfs can sustain warped tori of cool plasma, similar to other rapidly-rotating magnetic stars,” the team writes in a paper detailing their findings.
“Outstanding questions include whether dust clumps in these plasma tori explain CPV light curves, and whether the tori originate from the star or are fed by external sources,” the authors write, adding that estimates suggest that close to ten percent of M dwarf stars known to astronomers could host similar torus-shaped plasma structures early in their evolution.
The team’s paper, “A Plasma Torus Around a Young Low-Mass Star,” is available on the preprint server arXiv.org.
Caleb Hanks is a freelance writer, musician, and audio engineer based in Asheville, North Carolina.