Look Up

Life with a white dwarf star

by Mitchell Tester, College Student

As we know it, our solar system is currently the only harborer of life. But there is a possibility other solar systems in galaxies far away have the potential for life. Galaxies light years away…so far away, we could never even reach them in our lifetime, or any lifetime for that matter. With the power of telescopes, such as Hubble and JWST, we can see these galaxies, though, and within these distant galaxies exist solar systems far different from our own.

As I talked about in my “Fat Old Sun” two-part column, a star lives a life just as anything does. Our star, the Sun, will die out eventually after losing its capability of nuclear fusion, becoming a white dwarf. Stars larger than 10 times the mass of our Sun will become a neutron star, and ones larger than that will become a black hole. This white dwarf will be a fraction of the size of the Sun, roughly the size of the Earth. Although the Sun will eventually become a white dwarf, there are solar systems where these dead stars already exist!

It is estimated that there are over 10 million white dwarf stars in our galaxy alone. Within every solar system, there is a region around the star (or in some cases, stars) where there is a chance for life. This is denoted as the habitable zone (sometimes referred to as the Goldilocks zone). The habitable zone means there is the possibility for liquid water, meaning that the location of Earth is where our solar system’s habitable zone is. Venus is too hot, and Mars, likely once having liquid water, doesn’t anymore due to numerous possible factors, two being its small mass and the Sun’s radiation stripping away the atmosphere. The location of Earth and its mass is right to not only have liquid water, but sustain it unlike our smaller neighbor, Mars. Liquid water is the key to life, at least as we know it. Every solar system has a habitable zone. The location of the zone is largely dependent on the size of the star and its luminosity. Due to this fact, it is speculated that even dead stars—white dwarfs—have a habitable zone. What may that look like though?

Well, for starters, the habitable zone, or planet(s), would have to be very close to the white dwarf. Their day sky would look quite different from ours. Could you imagine what that may look like? A huge white ball in the sky, possibly much larger than our own due to it being closer. Instead of the yellow that our star emits, it would most likely be a bluish-white. This exoplanet would also most likely be tidally locked, meaning that one side would always see the white dwarf star. Similar to how we always see the same side of the Moon! Not only this, but the night sky would be much darker than ours, giving the inhabitants an opportunity to see so much more than us. Another spectacular sight would be the planetary nebula that surrounds the white dwarf. Planetary nebulas are the remnants of stardust after a star expels its surrounding layers when it dies, leaving the white dwarf behind and blasting everything else, painting it across the sky.

Although an exoplanet with life of any kind has never been found, if there were a planet that existed in a white dwarf’s habitable zone with life, it would prove that there could be life even after stellar death.

What it might look like from an exoplanet orbiting a white dwarf star.