News Astronomy

The North Star is much heavier than previously thought

Polaris is nearly 50 percent more massive than an earlier study found

A time-lapse photo of the night sky over Coyote Buttes, Ariz., shows stars leaving circular trails around a bright point in the middle, which is the North Star.

Stars appear to circle around the North Star in this time-lapse photo of the sky over Coyote Buttes, Ariz.

Scott Smith/Corbis Documentary/Getty Images Plus

By Ken Croswell

The star marking true north is a good deal heavier than we thought.

The North Star is 5.1 times as massive as the sun, astronomers report in work submitted July 12 to arXiv.org. That value, calculated from the motion of a much fainter star that orbits the luminary, is nearly 50 percent heavier than a recent estimate of 3.45