2024-08-23 03:26:07
Telescope images evaluated
Polarstern: Researchers make amazing discoveries
22.08.2024 – 14:54Reading time: 3 min.
The North Star is 450 light years away from Earth. Nevertheless, researchers were able to take a look at its surface – and discovered something amazing.
It is probably one of the most famous stars in human history: the North Star, also known as Polaris. Due to its fixed position above the North Pole and its relative brightness, it has always been considered a reliable orientation point for sailors and hikers in the northern hemisphere.
Due to its great distance from Earth – the North Star is around 450 million light years away – little was known about the celestial body for a long time. A companion star was not discovered until 1780 – so astronomers assumed for a long time that it was a binary star system.
Until 2006, when the next surprise came: images from the Hubble Space Telescope showed that the North Star itself is a double star – consisting of the brightly shining Polaris Aa and the dimly shining star Polaris Ab. The latter orbits its main star Polaris Aa about once every 30 years. The companion, discovered in 1780, is now called Polaris B.
Now a team of researchers led by astrophysicist Nancy Remage Evans from the Harvard-Smithsonian Astrophysical Observatory has discovered another previously unknown detail. With the help of the CHARA telescope network in California, the scientists were able to take a look at the surface of Polaris Aa.
The images showed spots that changed over time, the researchers wrote in their study published on the science platform “IOPscience”. All images of Polaris Aa taken by CHARA show spots on its surface that resemble those on our sun.
Since the spots could also be image artifacts that arose when the images were combined, for example due to missing data, the researchers compared the images with those of simulated models. However, the spots showed a lower contrast than those of the real images.
In addition, the real spots did not resemble the symmetrical pattern of the simulated ones, so the researchers concluded that the spots in the images taken by CHARA must be real sunspots.
Polaris Aa is a so-called Cepheid. This is a term for a so-called variable star that is characterized by regular fluctuations in brightness. These fluctuations are caused by pulsating changes in the diameter of the star. When the star contracts, it gets hotter and shines brighter; when it expands, it cools and shines less.
These brightness fluctuations make Cepheids of great astronomical importance, as they and the apparent brightness of the star from Earth can be used to calculate the distance of a celestial body. This in turn helps astronomers calculate the distances of entire star systems in our galaxy and in other galaxies.
Polaris Aa pulsates with a period of about four days, other Cepheids have a slightly longer pulsation period of up to 100 days. Compared to our sun, the Pole Star has a mass about 5.13 times greater – another finding by the researchers led by Remage Evans. This makes the Pole Star more massive than previously thought. It also has a diameter about 46 times greater than our sun.
“The mass in combination with the distance shows that Cepheid is more luminous than expected for this mass based on previous findings,” say the researchers. That is why the team wants to continue studying the North Star. Also to better understand how the spots on its surface are created.