North star 'Polaris' found to be covered in large dark spots

If you’ve ever gazed at the night sky, there’s no doubt you’ve set your sights on the North Star, also called Polaris. This impressive luminary has been a celestial guide for travel-weary navigators for centuries. 

Now, new research led by researchers at Georgia State University’s Center for High Angular Resolution Astronomy (CHARA) Array shines fresh light on this stellar beacon, uncovering fascinating details about its size, appearance, and rather unusual behavior.

Polaris star: An astronomical marvel

Found in the constellation of Ursa Minor, Polaris is not an average star. This celestial titan is the brightest member of a triple-star system and also a pulsating variable star. 

In a literal blink of an eye, Polaris can alternate between being brighter and fainter. This stellar light show stems from the star’s diameter swelling and shrinking over a four-day cycle.

Polaris: Cepheid variable star

Adding another feather to its cap, Polaris also happens to be a Cepheid variable star — one of the many standard candles of the universe.

These stars are of immense value to astronomers as their true brightness is linked to their pulsation period. 

Simply put, the brighter stars pulsate slower than their fainter counterparts. This information helps astronomers calculate the distances to galaxies and, more intriguingly, decipher the universe’s expansion rate.

Polaris investigation

The investigation, led by the phenomenal Nancy Evans at the Center for Astrophysics at Harvard & Smithsonian, employed the CHARA optical interferometric array of six telescopes at Mount Wilson, Calif.

Their prime objective? Map the orbit of the faint companion star that orbits Polaris every 30 years.

“The small separation and large contrast in brightness between the two stars makes it extremely challenging to resolve the binary system during their closest approach,” Evans expressed the complexities of the task.

Decoding the mysteries

The team’s research efforts were not in vain. Combining the light from the six telescopes at the historic Mount Wilson Observatory, the CHARA Array allowed the team to spot the elusive faint companion star as it passed Polaris. 

These scientific strides were made possible by the MIRC-X camera, designed by astronomers at the University of Michigan and Exeter University in the U.K. The device proved instrumental in capturing intricate details of stellar surfaces.

The images procured unveiled intriguing details about Polaris, the North Star. This study revealed that Polaris has a mass five times greater than that of our sun, making it a colossal celestial body.

Additionally, its diameter is an astonishing 46 times larger than our solar powerhouse, showcasing its immense scale and prominence in the universe.

Understanding such characteristics helps astronomers gain insights into stellar evolution and the dynamics of our galaxy.

Surprising findings

Other revelations about Polaris were also eyebrow-raising. “The CHARA images revealed large bright and dark spots on the surface of Polaris that changed over time,” said Gail Schaefer, director of the CHARA Array. This was never seen before on a Cepheid variable star. 

According to Gail Schaefer, director of the CHARA Array, these spots and the star’s rotation might be tied to a 120-day change in the star’s measured velocity.

“We plan to continue imaging Polaris in the future,” said John Monnier, an astronomy professor at the University of Michigan. “We hope to better understand the mechanism that generates the spots on the surface of Polaris.”

Implications of Polaris star research

Understanding Polaris extends beyond mere academic curiosity; it holds vital implications for the broader field of astronomy and our comprehension of the universe. 

The discoveries surrounding its size, luminosity, and peculiar surface characteristics enhance our understanding of stellar evolution and the dynamics of binary star systems. 

Furthermore, the insights gleaned from Polaris bolster the calibration of Cepheid variables as distance indicators across the cosmos. 

As researchers continue to refine their imaging techniques and unravel the complex behaviors of such stars, we inch closer to solving fundamental questions about the universe’s expansion, its structure, and ultimately, our place within the vast astronomical tapestry.

So, while Polaris continues to serve as a light in the night sky, the celestial curiosity it sparks in scientific minds is far from over. After all, where there’s a star, there’s a way.

The study is published in The Astrophysical Journal.  

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