White dwarfs can slow down cooling by forming crystals

Some white dwarfs, contrary to the laws predicted by physics, do not cool down for hundreds of millions of years. Recently, scientists have suggested that the reason for this is the formation of crystals in their thickness, which contribute to the redistribution of heat.

White dwarf. Source: www.caltech.edu

Strange behavior of white dwarfs

An article recently published in the journal Nature, authored by physicists from universities in the UK and Canada, offers a solution to a mystery that has been bothering scientists for several years. It concerns dead stars known as white dwarfs.

Accepted scientific theories claim that thermonuclear reactions do not occur in them. Therefore, they must gradually cool down over billions of years at a constant rate. Therefore, they can be used as an indicator of the age of the systems they are part of.

However, the observation carried out by the Gaia Space Telescope in 2019 challenged these ideas. It found that these stars hadn’t cooled for 8 billion years, which meant they had something inside that warmed them up.

Crystals inside dead stars

A new article is devoted to explaining how this can happen. The authors have developed a physical model that explains what can stop the cooling of white dwarfs. Scientists have noticed that some of these objects are formed not directly when the red giant drops its outer shells, but when smaller dead stars merge.

Physicists have found that in this case, chemical processes inside stars occur in an extremely unusual way and solid crystals form in the dense plasma. They have a higher density than the medium around them, so they do not sink.

Instead, these crystals begin to move towards the surface and displace the surrounding material in their path, which moves towards the center of the star. At the same time, a large amount of gravitational energy is released, which turns into mechanical energy, and then into thermal energy. It is the source that gives white dwarfs the opportunity not to cool down for billions of years.

According to phys.org

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