Scientists have long believed that once stars die, they become cold and passive. However, new research suggests that white dwarfs, which are the remnants of stars like our Sun, might actually keep their surroundings warm enough to support liquid water on nearby planets.
This finding expands the search for habitable worlds in our galaxy. Traditionally, we thought life could only thrive around active stars, but this idea is changing.
Thanks to powerful telescopes like the James Webb Space Telescope (JWST), researchers have already detected gas giants orbiting white dwarfs. This discovery confirms that planets can endure the violent death of their stars.
White dwarfs are smaller than our Sun but are incredibly dense, holding about half its mass. The Milky Way is estimated to have around 10 billion of these stars, and most stars will end their lives as white dwarfs.
Aomawa Shields from the University of California, Irvine, is leading this new research. She highlights how white dwarfs can emit residual heat, prompting a reevaluation of their capacity to support life. "If rocky planets exist in their vicinity, they could have more habitable regions than we believed," she says.
Shields and her team used advanced climate models to simulate two hypothetical ocean-covered planets. One planet orbited a super hot white dwarf, while the other orbited a main-sequence star, like our Sun. Both planets were placed in positions where they would receive similar amounts of sunlight.
An interesting twist arises from their orbits: the planet around the white dwarf completes a rotation every 10 hours, while the other takes 155 days. This rapid rotation on the white-dwarf planet leads to stronger winds, which circulate heat more effectively. It resulted in a temperature that was about 25°C warmer than its counterpart.
These findings indicate that rapid rotation may allow for better climate conditions, particularly for life. Regions at the boundary between day and night on these planets, known as the terminator line, could present optimal conditions for life due to better temperature regulation.
The research brings us to a pivotal moment. In 2020, astronomers found a Jupiter-sized planet orbiting a white dwarf, proving these celestial settings can host planets. The Webb telescope has more discoveries in the pipeline, suggesting we may soon find many rocky worlds that could harbor life.
As we look ahead, it’s exciting to think that white dwarfs might provide a stable environment for planets. If just a fraction of these stars have temperate planets, that could mean billions of potential homes for life in our galaxy. The hunt continues, pushing the boundaries of what we know about habitable zones in space.
Read the full study in The Astrophysical Journal here.