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Planets orbiting dead stars may be candidates for studying life

  • June 20, 2024
  • 3 min read
Planets orbiting dead stars may be candidates for studying life

The remains of dead stars that have used up the last of their fuel could be the excellent backdrops to study planets with sufficient water to support life. The challenge is finding the shadow of the planet that has “withered to a fraction of its size” and finding a planet that has held on to its water oceans long after the star has gone through its supernova phase.

A new study on the dynamics of white dwarf systems has suggested that, theoretically, some watery planets could survive and are out there awaiting discovery and closer scrutiny. The study came from the University of Wisconsin-Madison and is titled “Watery planets orbiting dead stars may be good candidates for studying life.”

Astronomers examining planets outside of our own solar system, known exoplanets, for signs of life gather data while those planets pass in front o their star. The light from the star that passes through the thin layer of atmosphere o the planet can reveal which elements and molecules are contained within the planet.

A huge star with powerful nuclear fusion can be challenging to examine. So finding a planet orbiting a smaller white dwarf makes is a much less daunting task.

The first hurdle for the planet is to survive the final phase of the life of a small- to medium-sized star like the sun as these can be rough. When stars like this run out of fuel that powers the nuclear fusion in their core, they reach an enormous size.

If a planet escapes being swallowed by the star, it’s still not completely safe. What follows is the loss of the star’s mass and a huge spike in its brightness. An Earth-like planet needs to be five to six times the distance that the Earth currently sits away from the star, known as an astronomical unit or AU. This would allow it to retain enough water to support life through this phase.

But over the next billion or so years, the star will shrink and cool, presenting an additional challenge to any life on the planet. The white dwarf will eventually become so small and cold that for any planet to get enough heat, it needs to be 1% of an astronomical unit away.  

More study on white dwarf stars and the planets that orbit them will be needed if we are to find out whether life can be supported in such a world.

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