For the first time, astronomers have recorded a video that shows the evolution of stellar spots on a star other than our sun, collecting footage using the STELLA robotic telescopes stationed at the Canary Islands over a six-year span to create the stunning footage released Tuesday.
The movie was the work of researchers at the Leibniz Institute for Astrophysics Potsdam (AIP) in Germany. They collected highly-sampled, phase-resolved spectroscopic data, then compiled it into a film showing the growth and fade of giant stellar spots on XX Triangulum, an active giant star also known as HD 12545 or XX Tri, and is located about 1,500 light years from Earth.
Their research revealed that XX Tri, which is about 10 times larger and twice as massive as the sun, has an underlying magnetic cycle with a period similar to that of the solar system’s central star but much stronger. The star also has a rotation period of 24 days, which became a factor as the AIP astronomers were unable to directly observe spots on the surface of this distant star.
Doppler imaging, mathematical models used to capture spectra
Instead, they had to rely upon Doppler imaging and mathematical models in order to resolve the stellar surface of the XX Tri indirectly. To obtain a single image of the stellar surface, the researchers had to observe it using the STELLA telescopes every night during that 24-day period of rotation, collecting a total of 667 usable spectra from July 2006 through April 2012.
Those spectra were complied into a movie of the stellar surface, showing a total of 86 rotational periods of the star and capturing its surface in three different projection styles: spherical or “real view”, which is what it would look like to the human eye; a Mercator projection that shows all of the surface at once; and a “pole-on view” from the perspective of a visible rotation pole.
“The movie shows a star-spot distribution with ever changing morphology,” the AIP said in a statement, “such as spot fragmentation and spot merging, and with apparently a large range of variability timescales. The decay rate of (magnetic) star spots is of great interest as it is directly related to the magnetic diffusivity in the convective layer of the star, which itself is a key quantity for the length of a magnetic-activity cycle.”
“We can see our first application as a prototype for upcoming stellar cycle studies, as it enables the prediction of a magnetic-activity cycle on a dramatically shorter timescale than usual,” added Andreas Künstler, who worked on the project. A paper on his team’s findings has been published by the journal Astronomy & Astrophysics.
You can download and watch the movie here.
—–
Feature Image: A. Künstler, T. A. Carroll, and K. G. Strassmeier, Leibniz Institute for Astrophysics Potsdam (AIP)
Comments