Astronomers have discovered on the surface of very hot stars in globular clusters giant magnetic spots, and also registered coming from them heavy duty flash. Open, which is reported in Astronomy Nature, will help scientists to explain the behavior of other similar objects — for example, white dwarfs.
Star half the Sun, but in 4-5 times it is called hot stars, extreme horizontal branch — because of their position on the diagram of Hertzsprung — Russell. They differ from other objects very thin hydrogen shell, and usually pass by one of the final stages of the life of a typical star (asymptotic branch of giants) who die prematurely.
For a long time these strange objects was uncharted, but now astronomers under the leadership Associated Momani (Yazan Momany) of the Astronomical Observatory in Padua, managed to identify to study very hot stars among the colder the study of hot stars in three globular clusters in the near-ultraviolet range. Observations were conducted using the Very large telescope (VLT) and the VLT Survey telescope.
The stars in globular clusters studied no companions showed up — which is quite surprising, as it is believed that in our galaxy the stars are extreme horizontal branch, usually found in binary systems. In addition, during prolonged monitoring of celestial bodies Momani and his colleagues recorded regular changes in brightness with periods from just a few days to several weeks.
By excluding all other possible scenarios, the researchers came to the conclusion that the observed variability can be explained by the presence of spots. Like sunspots, they are created magnetic fields, but between them there are big differences. In contrast to the Sun where spots appear dark against a bright and hot environment, the spots on the stars, extreme horizontal branch brighter and hotter than their surroundings. In addition, these spots are much more sun, they cover up to a quarter of the stellar surface, but also very robust: they hold for decades, while dark sunspots is a short-lived education that exist from several days to several months. When hot stars are rotating spots on the surface that appear in the field of view, then disappear from it, which leads to observed changes in gloss.
In addition to the variability of the gloss associated with the stains, scientists have discovered a pair of stars extreme horizontal branch, where there is a heavy duty flash. During these outbreaks were allocated several million times more energy than similar phenomena in the Sun, which also indicates the presence of a magnetic field.
Astronomers hope that the findings will help to explain the origin of strong magnetic fields many white dwarfs — objects that represent the last stage of the life of sun-like stars and having a lot in common with the stars, extreme horizontal branch. “Importantly, the changes in brightness of all hot stars, from young stars like the Sun to old stars extreme horizontal branches and long-dead white dwarf can now be linked with each other. All these objects can have a surface magnetic spot”, — says team member David Jones (David Jones), fellow of the Institute of astrophysics of the Canary Islands in Spain.
In the Sun the stains associated with the 11-year cycle of activity — change of the periods with a large number of spots and periods of almost complete absence. Recently, scientists recorded a spot which belongs to a new, 25-th solar cycle, which means the Sun slowly begins to get out of a deep minimum of activity, which was observed before.