A recent study published in the Astrophysical Journal takes a new look at sunspots in order to understand stellar activity and the potential for life in other solar systems. Sunspots refer to the darkened patches on the Sun which are caused by its magnetic field.
"The Sun is our closest star. Using solar observing satellites, we can resolve signatures on the surface 100 miles wide," said Vladimir Airapetian, a co-author on the new study and astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "On other stars, you might only get one pixel showing the entire surface, so we wanted to create a template to decode activity on other stars."
In order to do so, the scientists looked at images of sunspots using high-resolution data of the Sun from NASA's Solar Dynamics Observatory and JAXA/NASA's Hinode mission. They then converted these images into single datapoints in order to track how the light changed as the sunspot passed across the Sun's rotating face, a phenomenon called light curves.
The result was a simulation of what a passing sunspot on the Sun would look like if it were many light-years away; in other words, it allowed the team to visualize how a sunspot would look like on a distant star. "We wanted to know what a sunspot region would look like if we couldn't resolve it in an image," said lead author Shin Toriumi, a scientist at the Institute of Space and Astronautical Science at JAXA. "So, we used the solar data as if it came from a distant star to have a better connection between solar physics and stellar physics." The video below shows the images.
We know that sunspots often lead to solar flares, but the researchers wanted to better understand the environmental conditions of sunspots that bolster these intense outbursts of energy. By analyzing the light curves in x-ray and ultraviolet light, the researchers were able to see the atmosphere above the sunspots in the images. From these images, they determined that while there is some brightening of the atmospheres above sunspots as they are magnetically heated, the heating may also trigger a dimming in the lower temperature atmosphere. This information could be useful in determining the environments of spots on other stars.
This study focused specifically on images with only one sunspot visible. In the future, the team would like to extend their investigations to more complex modeling. "So far we've done the best-case scenarios, where there's only one sunspot visible," Toriumi commented. "Next we are planning on doing some numerical modeling to understand what happens if we have multiple sunspots."