Scientists collect high-resolution images of the North Star's surface for 1st time

In our solar system, scattered across one of Earth's verdant mountains, six eggshell-white telescopes gaze into the deep universe. As one cohesive hive, the domed structures collect cosmic light to guide modern astronomers exploring space — and it is thanks to this hive that we now have a brilliant new perspective on the light that guided astronomers of the past: the North Star.

Our visual knowledge of the current North Star (because of Earth's axial wobble, the title passes to different stars over the eons) runs deep. Artists, old and new, have depicted Polaris shining in their paintings, astrophotographers have imaged it from their backyards and scientists have pointed their instruments at it for decades. But what's special about these new Polaris views, courtesy of the CHARA Array on Mount Wilson in California, has to do with resolution. The special thing about CHARA is, as touched on, its telescopes work in tandem with one another. Their light data is combined in a central facility to provide one whole, clear picture of a source. It's as though the sextet of worker telescopes forms one ultimate telescope with a diameter of 330 meters (1,083 feet). And because of this, the project's image resolution — specifically, angular resolution — is excellent.

Sure enough, after checking out some of these Polaris images, put together with CHARA observations taken between 2016 and 2021, scientists found some previously unknown features of the star. Most notably, there are discernable spots on the star's surface, kind of like the sunspots we see on the sun every now and then.

"The CHARA images revealed large bright and dark spots on the surface of Polaris that changed over time," Gail Schaefer, director of the CHARA Array, said in a statement.

One of the major reasons this finding came as a surprise has to do with the fact that Polaris isn't any old star. It's a sort of star known as a Cepheid variable, which means it brightens and dims periodically. Polaris in particular gets brighter and fainter according to a four-day cycle, and scientists love locating Cepheids due to such very predictable behavior. That's because it allows these stars to be used for cosmic distance measurements. Basically, watching the change in a Cepheid's brightness over one cycle can reveal its true brightness.

Related: 'New star' as bright as the North Star will ignite in the sky this year. Here's how to see it.

By contrast, without predictably periodic pulsations, a star wouldn't be very reliable for such measurements. At risk of simplification, a dim star, for instance, could be either far away or just small — or, it could be weirdly dim for some other reason. Or, it could just happen to be dim during the time at which it was observed.