When it comes to the North Star, astronomers disagree on its size, its age, and its distance from Earth. Polaris, the star’s formal name, sits directly above the North Pole, pulses regularly in both diameter and brightness, and outshines its sister, Polaris B, which orbits around it once every 26 years. Traditional methods of measurement indicate the North Star is nearly seven times larger than the sun, Hilding Neilson, an astrophysicist at the University of Toronto, told Live Science. But other calculations that factor in the orbit of Polaris B and new measurements from the Hubble Space Telescope indicate the star is only 3.45 times larger than the sun. And astronomers can only calculate a star’s distance from Earth if they know it’s size.
Stars in binary systems, like Polaris and Polaris B, usually formed at about the same time. But calculations show Polaris B is much older than its bigger sibling. In a recent study, researchers generated a massive set of computer models trying to make sense of the conflicting data but did not succeed.
Studying Polaris poses a special difficulty because it lies outside the field of view for most telescopes and is too bright for the type of instruments that can precisely measure a star’s properties. “It’s blinding for them,” Neilson said.
He also noted, although unlikely, the North Star may have originated from two stars that slammed together and produced a rejuvenated star that appears younger than it is.
“It is challenging to draw significant conclusions beyond the fact that Polaris continues to be an enduring mystery, and the more we measure the less we seem to understand,” the researchers said. —J.B.