Something’s up with the North Star.
People have watched the North Star for centuries. The bright star, also known as Polaris, is almost directly above Earth’s North Pole and serves as a landmark in the sky for travelers without a compass. It’s also Earth’s closest cepheid, a type of star that pulses regularly in diameter and brightness. And Polaris is part of a binary system; it’s got a dimmer sister, known as Polaris B, that we can watch circling it from Earth.
“However, as we learn more, it is becoming clear that we understand less” about Polaris, wrote the authors of a new paper on the famous star.
The problem with Polaris is that no one can agree on how big or distant it is.
Astrophysicists have a few ways to calculate the mass, age and distance of a star like Polaris. One method is a stellar evolution model, said new study co-author Hilding R. Neilson, an astrophysicist at the University of Toronto. Researchers can study the brightness, color and rate of pulsation of the star and use that data to figure out how big and bright it is and what stage of life it’s in. Once those details are worked out, Neilson told Live Science, it’s not hard to figure out how far away the star is; it’s fairly simple math once you know how bright the star really is and how dim it looks from Earth.