For the first time, scientists have captured high-resolution images of Polaris, the North Star, revealing unexpected surface features.
The images, obtained using the CHARA Array at Mount Wilson, California, show large bright and dark spots on the star’s surface, challenging previous assumptions about this iconic star.
Surprising Discoveries on Polaris’ Surface
Polaris, long known for its near-constant position in the night sky, has now been revealed to have an unexpectedly dynamic surface. Using the CHARA Array, a system of telescopes functioning together to create a giant, high-resolution telescope, astronomers were able to resolve details on Polaris’ surface for the first time.
The team discovered large spots—both bright and dark—on the star, similar to the sunspots we observe on our Sun. These spots appear to change over time, introducing a new element to our understanding of Cepheid variable stars, of which Polaris is a prime example.
Cepheid variables are known for their regular pulsations—periodic expansions and contractions of their outer layers that cause predictable variations in brightness. Polaris, for instance, has a pulsation period of around four days. These pulsations have made Cepheids crucial for measuring cosmic distances, as their brightness fluctuations can be used as standard candles to gauge the scale of the universe.
However, the discovery of surface spots on Polaris suggests that there may be more factors influencing its brightness than just its pulsation cycles. According to Gail Schaefer, director of the CHARA Array, “The CHARA images revealed large bright and dark spots on the surface of Polaris that changed over time.” This suggests that the magnetic activity associated with these spots could be affecting the star’s luminosity in ways that have yet to be fully understood.
Unveiling Polaris’ Mass and Complexity
In addition to revealing surface features, the study also provided new insights into the mass and structure of Polaris. Previous estimates placed Polaris’ mass at several times that of the Sun, but recent observations suggest that it may be up to five times more massive.
Polaris is also a massive star, about 46 times the size of our Sun, and part of a triple-star system. This complexity adds another layer of intrigue, as its binary companion star orbits Polaris every 30 years, making it difficult to study directly due to the small separation and large contrast in brightness between the two stars.
The discovery of Polaris’ increased mass has raised new questions for scientists. It implies that the star is more luminous than previously thought, which could challenge existing models of Cepheid stars. According to astronomer Nancy Evans of the Center for Astrophysics at Harvard & Smithsonian, “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.” This complexity suggests that our understanding of Cepheid variable stars, and perhaps stellar evolution in general, may need to be revisited.
Future Research Directions
The discovery of these surface spots on Polaris, combined with the new understanding of its mass and complexity, opens up exciting possibilities for future research. Scientists now plan to conduct further observations of Polaris to better understand the nature of these spots and their impact on the star’s behavior.
According to John Monnier, an astronomy professor at the University of Michigan, “We plan to continue imaging Polaris in the future... to better understand the mechanism that generates the spots on the surface of Polaris.” These future studies could provide critical insights into the role of magnetic fields in the behavior of Cepheid variables.
This research also holds promise for improving our understanding of other stars. By studying Cepheid stars like Polaris, which serve as cosmic distance markers, astronomers hope to refine their techniques for measuring the universe’s scale and gain deeper insights into the life cycles of stars.