Astronomers Found That Hot Stars Are Troubled by Massive Magnetic Spots

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Astronomers utilizing the European Southern Observatory (ESO) telescopes have found massive spots on the surface of hot stars wrapped in stellar clusters. 

Those stars are troubled by magnetic spots, while others encounter explosions of energy several million times more energetic than the eruptions on the Sun. Here are the latest details. 

 The Horizontal Branch Stars Situation

A team of astronomers looked at a specific type of star dubbed the extreme horizontal branch stars – space objects with almost half the mass of our host star but more than four times hotter. These hot stars are unique because they bypass one of the final stages of a typical star’s life and die prematurely. In our galaxy, these odd space objects are associated with the presence of a nearby companion star. However, when observed in lightly packed stellar groups known as global clusters, the vast majority of these stars don’t have a companion. 

The team’s long-term monitoring of those stars, realized with ESO telescopes, also unveiled that something more peculiar is happening. Many extreme horizontal branch stars within them displayed constant changes in their brightness in only a few days. 

“After eliminating all other scenarios, there was only one remaining possibility to explain their observed brightness variations: these stars must be plagued by spots!” explained Simone Zaggia, a former ESO Fellow and study co-author from the INAF Astronomical Observatory of Padua in Italy. 

Spots on extreme horizontal branch stars seem to be very different from the dark sunspots on our host star, but both are triggered by magnetic fields. The spots on these extreme stars are hotter and brighter than the surrounding stellar surface, unlike the Sun, where the spots are cooler and dark. 

Besides the brightness variations because of the spots, the astronomers also found some extreme horizontal branch stars that showed superflares – explosions of energy. 

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