Newly discovered 'fountain of youth' phenomenon may help stars delay death by billions of years

White dwarfs are the stars that will be left behind when stars like the sun "die," smoldering away in space as cooling stellar embers.

Recent observations indicated that some of these stellar corpses may actually take longer to cool off than previously expected. This means that white dwarfs may have a way of generating energy after their "deaths," defying the classical picture of them being inert dead stars. As a result, some white dwarfs could actually be billions of years older than currently estimated.

Analyzing data from the Gaia space mission in 2019, scientists discovered a population of white dwarfs that seem to have stopped cooling for billions of years. Now, a team of researchers led by Antoine Bédard from the University of Warwick and Simon Blouin from the University of Victoria think they know what mechanism lies behind this baffling discovery.

The fountain of stellar youth

White dwarfs are born when stars that possess around the same mass as the sun exhaust the fuel supply necessary for nuclear fusion at their cores. This supply is made up of the universe's lightest element: Hydrogen. The end of fusion, aka the conversion of hydrogen to helium, in the stellar core also cuts off the energy that has pushed outwards and protected the star from collapsing under its own gravity for often billions of years.

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Crushed by gravity, the outer layers of the star where nuclear fusion is still happening are ripped away. These layers "puff out" to tens, or even hundreds, of times the original radius of the star during what is known as the red giant phase of the star's life. Eventually, these surrounding layers disperse, leaving the cooling, exhausted stellar core behind as a white dwarf.

For the sun, this transformation will begin in around 5 billion years; the red giant phase of our star will see it swell out to the radius of Mars. During this time, the sun will end up swallowing the inner planets, including Earth. 97% of the stars in the Milky Way will undergo the same basic process to become white dwarfs.