Groundbreaking Discovery: White Dwarf Stars Can Live for Billions of Years Longer Than Previously Thought New Study Challenges Belief That White Dwarf Stars Are 'Dead' - Thanks to Floating Crystals! . Credit: scitechdaily.com

When flipping through an astronomy textbook, you will likely come across a section discussing white dwarf stars, which are often referred to as "dead stars" that gradually lose heat over time. However, recent findings published in the journal Nature challenge this commonly held belief.

Using data from the European Space Agency's Gaia satellite, researchers from the University of Victoria (UVic) and their collaborators have discovered why a group of white dwarf stars have ceased to cool for more than eight billion years.

Co-principal investigator and Canadian Institute of Theoretical Astrophysics National Fellow at UVic, Simon Blouin, explains, "We have found that the conventional view of all white dwarfs being dead stars is not entirely accurate. In order for these stars to stop cooling, they must have a source of extra energy. While we were unsure of how this was happening, our new research provides an explanation for this phenomenon."

Gaining a better understanding of the age and other characteristics of white dwarf stars allows scientists to better reconstruct the formation of the Milky Way Galaxy. Using data from Gaia in 2019, Blouin worked alongside Antoine Bédard from the University of Warwick and Sihao Cheng from the Institute for Advanced Study to make this groundbreaking discovery.

  1. It is estimated that over 97 percent of stars in the Milky Way will eventually become white dwarfs. For a long time, these stars have been regarded as being at the end of their life cycle. Once they have depleted their nuclear energy source, they no longer produce heat and gradually cool down until the dense plasma in their interiors solidifies, causing the star to solidify from the inside out. This cooling process can take billions of years.

    However, the recent study suggests that in some white dwarfs, the solid crystals formed during the freezing process are less dense than the surrounding liquid, causing them to float upwards. As a result, the heavier liquid is forced downwards, releasing gravitational energy that interrupts the cooling process and can prolong the star's life for billions of years.

    "This is the first time we have observed this transport mechanism in any type of star, which is very exciting as it is not often that we come across a new astrophysical phenomenon," says Bédard, a Research Fellow at the University of Warwick.

    • The reason why this phenomenon occurs in some stars and not others is still unknown, but Blouin suggests that it could be due to the composition of the star. "Some white dwarf stars are formed when two different stars merge. This collision changes the composition of the star in a way that allows for the formation of floating crystals," explains Blouin.

      White dwarf stars are commonly used as age indicators, with the general belief being that the cooler the star, the older it is. However, with the discovery of this additional delay in cooling, some stars of the same temperature may actually be billions of years older than previously thought, forcing astronomers to reconsider how they determine the age of stellar populations.

      "This groundbreaking discovery not only requires a revision of astronomy textbooks, but also prompts astronomers to reevaluate their methods for determining the age of stars," concludes Blouin.

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