Astronomers have solved the mystery of overly hot blue stars

How the artist saw the violation of the formation of a young star passing old

Australian astronomers explained the phenomenon of too hot blue stars that were found in densely populated star clusters. These stars had a very strong brightness - which means they were very hot. But at the same time their mass did not exceed 50% of the mass of the Sun, which in no way corresponded to their observed temperature.

Most stars fit into the “main sequence” on the mass and temperature diagram - the higher the mass, the stronger they heat up, and the brighter they shine - and the faster they burn. Most of the anomalies, without which no beautiful graph can do, have already been explained.
')
But until now, the behavior of the stars located at the end of the horizontal branch of the diagram, known as the "blue hook stars", was not clear. They are not very big and not very bright, but at the same time extremely hot. Scientists have suggested that the reason for this was the event that occurred at an early stage of their development - and the consequences of this event manifest themselves through millions of years, towards the end of the life of the stars.


Chart with a horizontal branch

In the depths of most stars, hydrogen is converted to helium. And in the stars of the blue hook, helium turns into carbon — and for this, it is necessary to reach temperatures in the core of more than 100 million degrees. In the old stars, helium is also transformed, but at temperatures two times smaller than those of the blue hook stars.

Scientists from the Australian State University believe that in the process of forming such a star from a gas disk, another star flying past caused a violation of the disk. As a result, the newly formed star spins faster than it normally does when forming a star without external influences. Rapid rotation compensates for the force of gravity, compressing the star, so it burns hydrogen fuel more slowly, and the process of its life is different from the life of ordinary stars. These stars are so hot that most of the energy emitted in the ultraviolet range - so in the visible range, they look pretty dim.

And there should be a relatively large number of instances of foreign stars flying in densely populated areas of star clusters. This is confirmed by early studies that refute the point of view according to which all the stars in clusters were formed at about the same time. In fact, in such clusters there are several generations of stars - and older generations intervene in the formation of the younger ones.