Newly discovered phenomenon could change how scientists understand stellar age
As with most celestial bodies, stars follow a cycle of formation, evolution and eventual extinction. To the white dwarfsfor example, are considered “dead stars” because they exhaust their nuclear energy, cease heat production and begin a cooling process that can last for billions of years.
However, in 2019, data from the European Space Agency’s (ESA) Gaia satellite revealed a cluster of white dwarfs that mysteriously stopped cooling 8 billion years ago, as if they had found the “fountain of youth”. This phenomenon was described in an article published in the journal Nature on March 6.
According to the Galileo portal, scientists were intrigued by the possibility of an apparent “dead star” continue generating extra energy that would slow down their cooling. To better understand this stage in the life of white dwarfs, researchers from the University of Warwick, in the United Kingdom, and the University of Victoria, in Canada, conducted investigations.
Traditionally, the process of stellar cooling occurs when the dense plasma inside the star begins to solidify, initiating a solidification process from the inside out. However, the study revealed that the plasma of some white dwarfs does not follow this pattern.
Instead, the solids formed, being less dense than the surrounding liquid, tend to float. As these crystals rise, they displace the heavier liquid downward, releasing enough gravitational energy near the star’s core to stop cooling for billions of years.
The researchers hypothesize that this phenomenon may be the result of differences in the composition of stars. “Some white dwarfs are formed by the merger of two different stars. When these stars collide to form the white dwarf, it changes the composition of the star in a way that can allow floating crystals to form.” Simon Blouinone of the authors of the article.
It is estimated that more than 97% of the stars in the Milky Way will eventually become white dwarfs. Currently, these stars are used as stellar age markers: the colder a white dwarf, the older it is supposed to be.
However, the scientists’ discovery will imply a revision of this concept, as the delay in the cooling of some white dwarfs suggests that not-so-frozen stars may be much older than previously thought.
+ Check out the complete study here.
