White dwarf stars could host life-supporting planets, study finds

The search for habitable planets has taken a leap forward with new space telescopes probing exoplanet atmospheres for life. The James Webb Space Telescope (JWST) has begun analyzing distant worlds, while future instruments, such as the Nancy Grace Roman Telescope, will expand the search.

Advanced ground-based observatories, including the Extremely Large Telescope and the Giant Magellan Telescope, will also enhance detection capabilities. These technological advancements make it increasingly likely that astronomers will soon find evidence of life beyond Earth.

Traditionally, stars similar to the Sun have been considered the most promising candidates for hosting life-bearing planets. However, red dwarfs and brown dwarfs have also been studied due to their abundance and longevity. White dwarfs—stellar remnants left after stars exhaust their fuel—offer another intriguing possibility.

About 97% of stars in the Milky Way will eventually become white dwarfs. While they no longer generate energy through fusion, they release residual heat and cool over time. This cooling process is complex, as crystallization within the star slows energy loss, potentially extending the period during which a planet in its habitable zone could support life.

The transition of a star into a white dwarf can be catastrophic for surrounding planets. The process causes major changes in the star’s mass and radius, destabilizing planetary orbits. Many planets may be lost or destroyed, as evidenced by the presence of planetary debris around white dwarfs.

Studies suggest that up to 50% of white dwarfs show signs of accreted planetary material, indicating that many planets do not survive the transformation. However, some mechanisms could allow planets to remain intact, such as gravitational interactions with other celestial bodies.

Seven exoplanets have already been detected orbiting white dwarfs, and researchers expect more discoveries in the coming years.

One of the most critical factors in determining a planet’s potential for life is its position in the habitable zone, where conditions allow liquid water to exist. Unlike main-sequence stars, white dwarfs experience continuous cooling, meaning their habitable zones shift over time. A planet must be close to a white dwarf to receive sufficient heat, but this poses challenges, as the post-main-sequence evolution may have disrupted this region.

Scientists have explored whether an Earth-like planet in the white dwarf habitable zone could maintain suitable conditions for life.

A recent study led by Florida Tech researcher Caldon Whyte examined the ability of such planets to support both photosynthesis and ultraviolet (UV)-driven abiogenesis, a process thought to play a role in the origin of life on Earth.

His findings, published in The Astrophysical Journal Letters, suggest that for a typical white dwarf with a mass of 0.6 times that of the Sun, an Earth-like planet located at approximately 0.012 astronomical units (AU) could remain in the habitable zone for nearly 7 billion years—longer than Earth has supported life.

Whyte's model calculated whether planets in these zones would receive enough energy for photosynthesis and UV-mediated chemical reactions necessary for life. His results indicated that these energy levels remained sufficient throughout the habitable period, an exciting discovery for astrobiologists.

White dwarfs' small size makes detecting their exoplanets challenging. Although their reduced luminosity enhances transit visibility, the likelihood of detecting Earth-sized planets remains low. Current technology has identified larger gas giants around white dwarfs, but future missions could refine searches for smaller, rocky planets.

Whyte's findings may reshape the search for life beyond Earth. If white dwarfs can sustain habitable conditions for billions of years, they represent valuable targets for astronomers.

The JWST has already proven instrumental in detecting Jupiter-like planets through direct imaging and mid-infrared observations. The MEOW survey has also identified a potential exoplanet candidate orbiting a white dwarf at a promising distance.

Whyte hopes to use JWST to locate white dwarfs that match his model’s predictions. If a suitable candidate is found, astronomers can search for planets within its habitable zone. Even if planets are not detected, data from these studies will help refine future search efforts, ensuring that telescope time is directed toward the most promising systems.

“We’re giving researchers confidence that these star systems are worth exploring,” Whyte said. “Whether we find planets or not, every piece of data brings us closer to understanding where life might exist.”

The discovery of potentially habitable planets around white dwarfs challenges previous assumptions about where life might thrive. While the search for life in the universe is ongoing, white dwarfs provide an exciting new frontier.

With telescopes becoming more advanced, the next decade may yield groundbreaking discoveries that bring us closer to answering one of humanity’s oldest questions: Are we alone in the universe?

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