In a groundbreaking piece of research, scientists have been able to image sunspots on a distant star as it rotates, a first for astronomy. And the discovery could help us understand the evolution of our own Sun.
The findings, published in Nature, were made on the star Zeta Andromedae, found in the Andromeda constellation 181 light-years from Earth. Led by the University of Michigan and the University of Exeter, scientists used a novel technique known as interferometry to obtain the images, which involved using multiple telescopes on Earth to create the observational power of a 330-meter-wide (1,080-foot-wide) telescope.
Interestingly, the sunspots on this star, called starspots, were found to be highly erratic. On the Sun, must sunspots are found in bands around its equator. They are caused when strong regions of the magnetic field create cooler and darker patches on the surface, blocking the flow of heat and energy.
But on Zeta Andromedae, which rotates once every 18 days, the sunspots were found to appear all over the star. Despite the star being ancient, the scientists behind the discovery said that it seemed to be behaving like a young star, possibly giving an insight into how our Sun behaved early in its life.
This is not the first time sunspots have been imaged on another star, but it is the first time spots have been seen to cover the poles and other regions of a star. In addition, it is the first time sunspots during a star’s full rotation period have been imaged, rather than a single snapshot.
The star's entire 18-day rotation was imaged, a first for astronomy. Roettenbacher, Monnier, et al.
“It’s important to understand the Sun’s history because that dictates the Earth’s history – its formation and the development of life,” said the University of Michigan's Rachael Roettenbacher, the study’s lead author, in a statement. “The better we can constrain the conditions of the solar environment when life formed, the better we can understand the requirements necessary for the formation of life.”
In particular, the spots on Zeta Andromedae were found in its northern polar region, and also spread lower down. Our current understanding of the Sun’s magnetic field can’t explain how this happens, so it suggests different processes must be happening on other stars. In fact, it hints that the magnetic fields of stars like this can stop heat flowing across larger regions, rather than just in the spots themselves. This could have implications for measuring the temperatures of distant stars, which we use to determine their age.
For now, though, the images themselves are just rather impressive. We’ve managed to actually view the rotation and processes taking place on a star more than a thousand trillion miles away. That’s pretty neat in itself.