This article was initially revealed at The Conversation. The publication contributed the article to Space.com’s Expert Voices: Op-Ed & Insights.
The solar will sometime die. This will occur when it runs out of hydrogen gas in its core and might not produce vitality through nuclear fusion because it does now. The demise of the solar is usually considered the top of the photo voltaic system. But in actuality, it could be the start of a brand new part of life for all of the objects residing within the photo voltaic system.
When stars just like the solar die, they undergo a part of fast enlargement known as the Red Giant phase: The radius of the star gets bigger, and its color gets redder. Once the gravity on the star’s surface is no longer strong enough for it to hold on to its outer layers, a large fraction – up to about half – of its mass escapes into space, leaving behind a remnant called a white dwarf.
I’m a professor of astronomy on the University of Wisconsin-Madison. In 2020, my colleagues and I discovered the first intact planet orbiting round a white dwarf. Since then, I’ve been fascinated by the prospect of life on planets round these, tiny, dense white dwarfs.
Researchers seek for indicators of life within the universe by ready till a planet passes between a star and their telescope’s line of sight. With gentle from the star illuminating the planet from behind, they’ll use some easy physics ideas to determine the varieties of molecules current within the planet’s ambiance.
In 2020, researchers realized they may use this method for planets orbiting white dwarfs. If such a planet had molecules created by residing organisms in its ambiance, the James Webb Space Telescope would most likely have the ability to spot them when the planet handed in entrance of its star.
In June 2025, I published a paper answering a query that first began bothering me in 2021: Could an ocean – probably wanted to maintain life – even survive on a planet orbiting near a useless star?
A universe filled with white dwarfs
A white dwarf has about half the mass of the Sun, but that mass is compressed into a volume roughly the size of Earth, with its electrons pressed as close together as the laws of physics will allow. The sun has a radius 109 times the dimensions of Earth’s – this dimension distinction implies that an Earth-like planet orbiting a white dwarf might be about the identical dimension because the star itself.
White dwarfs are extraordinarily widespread: An estimated 10 billion of them exist in our galaxy. And since each low-mass star is destined to finally turn into a white dwarf, numerous extra have but to type. If it seems that life can exist on planets orbiting white dwarfs, these stellar remnants might turn into promising and plentiful targets within the seek for life past Earth.
But can life even exist on a planet orbiting a white dwarf? Astronomers have known since 2011 that the habitable zone is extraordinarily near the white dwarf. This zone is the placement in a planetary system the place liquid water might exist on a planet’s floor. It can’t be too near the star that the water would boil, nor so distant that it could freeze.
The liveable zone round a white dwarf can be 10 to 100 times closer to the white dwarf than our personal liveable zone is to our Sun, since white dwarfs are a lot fainter.
The challenge of tidal heating
Being so close to the surface of the white dwarf would bring new challenges to emerging life that more distant planets, like Earth, do not face. One of these is tidal heating.
Tidal forces – the variations in gravitational forces that objects in house exert on completely different elements of a close-by second object – deform a planet, and the friction causes the fabric being deformed to warmth up. An instance of this may be seen on Jupiter’s moon Io.
The forces of gravity exerted by Jupiter’s different moons tug on Io’s orbit, deforming its inside and heating it up, leading to a whole lot of volcanoes erupting consistently throughout its floor. As a consequence, no floor water can exist on Io as a result of its floor is simply too scorching.
In distinction, the adjoining moon Europa can also be topic to tidal heating, however to a lesser diploma, because it’s farther from Jupiter. The warmth generated from tidal forces has prompted Europa’s ice shell to partially soften, leading to a subsurface ocean.
Planets within the liveable zone of a white dwarf would have orbits shut sufficient to the star to expertise tidal heating, just like how Io and Europa are heated from their proximity to Jupiter.
This proximity itself can pose a problem to habitability. If a system has multiple planet, tidal forces from close by planets might trigger the planet’s ambiance to entice warmth till it turns into hotter and warmer, making the planet too hot to have liquid water.
Enduring the pink large part
Even if there is just one planet within the system, it could not retain its water.
In the method of changing into a white dwarf, a star will increase to 10 to 100 instances its unique radius through the red giant phase. During that time, anything within that expanded radius will be engulfed and destroyed. In our own solar system, Mercury, Venus and Earth will be destroyed when the Sun eventually becomes a red giant before transitioning into a white dwarf.
For a planet to outlive this course of, it must begin out a lot farther from the star — maybe on the distance of Jupiter and even past.
If a planet begins out that distant, it could have to migrate inward after the white dwarf has shaped in an effort to turn into liveable. Computer simulations show that this kind of migration is possible, however the course of might trigger extreme tidal heating which will boil off floor water – just like how tidal heating causes Io’s volcanism. If the migration generates sufficient warmth, then the planet might lose all its floor water by the point it lastly reaches a liveable orbit.
However, if the migration occurs late enough within the white dwarf’s lifetime – after it has cooled and is not a scorching, brilliant, newly shaped white dwarf – then floor water might not evaporate away.
Under the appropriate situations, planets orbiting white dwarfs might maintain liquid water and doubtlessly assist life.
Search for all times on planets orbiting white dwarfs
Astronomers have not but discovered any Earth-like, liveable exoplanets round white dwarfs. But these planets are tough to detect.
Traditional detection strategies just like the transit technique are less effective because white dwarfs are much smaller than typical planet-hosting stars. In the transit technique, astronomers watch for the dips in light that occur when a planet passes in front of its host star from our line of sight. Because white dwarfs are so small, you would have to be very lucky to see a planet passing in front of one.
Nevertheless, researchers are exploring new strategies to detect and characterize these elusive worlds utilizing superior telescopes such because the Webb telescope.
If liveable planets are discovered to exist round white dwarfs, it could considerably broaden the vary of environments the place life would possibly persist, demonstrating that planetary methods might stay viable hosts for all times even lengthy after the demise of their host star.
This article is republished from The Conversation below a Creative Commons license. Read the original article.