Astronomers Observe Internal Wobbles Of Blue Supergiant Stars For The First Time

Simulation of the interior of a star three times as heavy as our Sun, which shows waves generated by turbulent core convection and propagating throughout the star's interior. Tamara Rogers 

The way a star shakes influences how it shimmers and researchers can use this relationship to work out what’s going on inside stars. This field is known as asteroseismology, and for the first time, astronomers have observed these stellar waves in a rare class of stars: blue supergiants.

These objects are often said to be living a “Rock & Roll” lifestyle because they live fast and die young. They are very massive and very hot, but science has struggled to fully constrain their properties and understand what makes them tick. As reported in Nature Astronomy, researchers are getting closer to bridging this gap in knowledge.

The team has been working for many years on the possible patterns of the stellar waves. Two were predicted; gravity waves (not to be confused with gravitational waves), which would ripple across the surface of the stars like waves in the sea, and deeper standing waves generated in the depths of the stars. The observations brought forth evidence for both of them.

“In line with our predictions, these latest observations have confirmed two types of waves which give us different information about the star,” co-author Dr Tamara Rogers, from Newcastle University, said in a statement. “Those which break at the surface, similar to the waves breaking on the beach, and the standing wave that just keeps on going and is similar to the seismic waves on Earth. From these, we can start to understand how the star is moving and rotating and the physics and chemistry of what is going on inside the deep interior, including the stellar core.”

The international team used the Kepler/K2 and TESS missions to observe the changes in light in 167 blue supergiants. The prolonged observations, not performed with any other instrument before, allowed the researchers to track changes in starlight and demonstrate that waves shaking the stars is the rule, not the exception.  

"The variability in these stars had been there all along, we only had to be patient and wait for modern space telescopes to observe them,” lead author Dr Dominic Bowman, from the KU Leuven Institute of Astronomy, explained. “It is as if the rock-and-roll stars had been performing the whole time, but only now opened the doors of their concert hall because of NASA space missions.”

The next step for this research is obtaining more detailed observations of these stars. Researchers will need that data to construct models of how these waves affect stars. With those, they will be able to constrain the age, mass, internal composition, and dynamics of all the incredible blue supergiant stars out there.

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