White dwarfs are more mysterious than originally thought

The white dwarfs managed to question the theories that prevail about them.

There is a general theory that these cosmic objects are inert remnants of stars. It is thus an exposed star nucleus that is no longer able to burn hydrogen and slowly cool down (billions of years). But the Hubble Space Telescope has at least challenged this theory, thanks to detailed observations of two globular clusters – M3 and M13. Both clusters have many properties in common, including, for example, a high population of white dwarfs, the age of the stars, and similar composition. Thanks to this, both objects can be compared well.

Thus, astrophysicists used a Hubble wide-angle ultraviolet camera to compare white dwarfs between the two star clusters. In this way, they compared more than 700 of these celestial objects. The main difference between the two star clusters is that M3 contains a larger number of standard white dwarfs that are slowly cooling down. In contrast, M13 contains two different stellar populations, one group is made up of standard white dwarfs as we know it and the other is made up of dwarfs that have been able to retain hydrogen in their outer shell. It is this layer of hydrogen that should allow them to burn longer and thus cool more slowly.

This discovery may call into question measurements of the ages of galaxies and of the stars themselves, as white dwarfs burning hydrogen can deviate from previously used methods by up to one billion years. So far, scientists have used the relationship between the dwarf’s age and the temperature to calculate the cooling rate of this object.

Source: Phys.org,

Source: Technológie by pc.zoznam.sk.

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