A recent study, yet to be peer-reviewed and shared on arXiv.org on July 12, suggests that the North Star, Polaris, is significantly more massive than previously thought.
Mass of North Star Polaris
According to astronomers, Polaris is 5.1 times the mass of the sun, a figure that is 50% higher than the earlier estimate of 3.45 times the sun’s mass.
This revised mass has implications for our understanding of Polaris’ lifespan. Stars with greater mass burn through their nuclear fuel at a faster rate, leading to a shorter stellar life.
Age of Polaris
Based on the former mass estimate, Polaris was believed to be around 100 million years old. However, with the new data, it appears that Polaris may have formed more recently, though a precise age has yet to be determined.
The new mass estimate was made possible by observations of a dim companion star to Polaris, which had gone unnoticed until 2005.
Companion star’s orbit around Polaris
It was then observed by Nancy Evans and her team using the Hubble Space Telescope. Further observations were made in 2016 when the companion star came closest to Polaris, utilizing the CHARA array at Mount Wilson Observatory in California.
Given the companion star’s orbit around Polaris takes about three decades, most of its path has now been tracked, providing a solid basis for the mass calculation.
Observations made by Nancy Evans
Nancy Evans, affiliated with the Harvard and Smithsonian Center for Astrophysics, emphasized the lengthy process required for such an endeavor.
Polaris, located 447 light-years away, is the nearest example of a Cepheid variable star to Earth. Cepheids are significant in astronomy as they are used to measure cosmic distances.
These large and bright stars, nearing the end of their life cycles, periodically expand and contract, causing fluctuations in their brightness.
Cepheid’s Pulsation and rarity of Cepheid
The duration of a Cepheid’s pulsation is directly related to its luminosity, serving as a key to calculating distances to galaxies.
The finding underlines the critical nature of accurate mass measurements for Cepheids, allowing astronomers to refine their models of star evolution and enhancing our understanding of the universe’s scale.
Ed Guinan, an astronomer from Villanova University not involved in the study, highlighted the rarity of Cepheids with precisely determined masses, pointing to the importance of this discovery.