When astronomers think about whether distant planets could support life, they often focus on the planets themselves.
But a growing body of research shows that stars play an equally important role.
New work led by astronomer Luke Bouma reveals a surprising way to study how stars influence their planets—by observing giant rings of plasma that act like natural space weather stations.
Bouma, a researcher at Carnegie Science, is presenting the findings at the American Astronomical Society meeting, and the study is published in The Astrophysical Journal Letters.
The research focuses on M dwarf stars, also known as red dwarfs.
These stars are smaller, cooler, and dimmer than our Sun, but they are by far the most common type of star in the galaxy. Astronomers know that most M dwarfs host at least one rocky, Earth-sized planet.
Unfortunately, many of these planets appear hostile to life, often being scorched, stripped of their atmospheres, or bombarded by powerful flares and radiation.
Even so, M dwarfs provide a valuable opportunity to study how stars affect planetary environments. “Stars influence their planets in two major ways,” Bouma explained. “One is through light, which we can observe easily.
The other is through particles—things like stellar winds and magnetic storms—which are much harder to detect from far away.” In our own solar system, these particles play a major role in shaping planetary atmospheres, making them essential to understand.
Since scientists cannot place space weather instruments around distant stars, Bouma looked for a natural alternative. Working with Moira Jardine from the University of St Andrews, he studied a strange group of young M dwarfs called complex periodic variables. These stars show repeated dips in brightness that puzzled astronomers for years. Some thought the dimming was caused by starspots, while others suspected orbiting material.
By creating detailed “spectroscopic movies” of one such star, the team uncovered the answer. The dips are caused by huge clouds of cool plasma trapped by the star’s magnetic field. As the star spins, the magnetic field drags this material around, forming a giant ring—or torus—encircling the star.
Once this was understood, the mysterious dimming events became something far more useful. “These plasma rings effectively act as space weather stations,” Bouma said. They allow scientists to track where stellar material gathers, how it moves, and how strongly it is controlled by magnetic forces—all key factors in understanding how stars affect nearby planets.
The researchers estimate that at least 10 percent of M dwarfs have these plasma rings early in their lives. Next, Bouma hopes to determine where the material comes from and how it interacts with surrounding planets.
“We still don’t know whether planets around M dwarfs can host life,” Bouma said. “But it’s becoming clear that space weather will be a crucial part of the answer.”
Source: KSR.
