Giant Planet Survives Sun’s Death, Offering Insights Into Solar System’s Future

All stars face an eventual end, including the Earth’s sun. Scientists predict that the sun will expand into its red giant phase a few billion years from now, potentially engulfing nearby planets like Mercury and Venus. This phase poses a question: What will happen to Earth and other planets in our solar system?

Astronomers have made a breakthrough in understanding this process by discovering a giant planet that survived its sun’s death. Ryan J. MacDonald from the University of St Andrews shared insights with Newsweek: “The surviving planets around the sun will initially move further away when the sun dies, due to the leftover white dwarf having less mass than the sun. However, the giant planet we have studied, WD 1856b, has moved in closer to the white dwarf.”

The discovery of the planet WD 1856b orbiting a white dwarf intrigued scientists when it was first noted in 2020. Using NASA’s James Webb Space Telescope, they explored how this giant planet survived its sun’s demise. They reconstructed the planet’s journey and analyzed its atmosphere, observing methane and high-altitude hazes. These findings marked the first successful characterization of a planet’s atmosphere around a dead star, shedding light on the potential for atmospheres in similar planetary systems.

The planet initially orbited its star from a safe distance and only migrated closer billions of years after the star’s death. “Our findings have bearing on the long-term fate of our solar system,” said Christopher O’Connor from Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics. “In roughly five billion years, our sun will die, and we don’t know precisely what will happen to the planets at that time.” This discovery offers new possibilities for understanding habitable planets around dying stars.

WD 1856b, located approximately 80 light-years from Earth, is as large as Jupiter and orbits a star the size of Earth. When stars like our sun collapse, they become white dwarfs—dense remnants of their former selves. O’Connor noted that this planetary system is among the most unusual known, with the planet’s large radius and rapid orbit.

Researchers investigated two theories to explain WD 1856b’s position: surviving the star’s engulfing phase or gravitational influences drawing it closer later. The white dwarf is part of a triple star system, with outer companions possibly affecting its orbit. Their study, using NASA’s telescope, found the planet hotter than anticipated due to its proximity to the white dwarf and speculated it heated as it moved in.

MacDonald explained that this discovery suggests giant planets in our solar system might migrate closer to the sun’s remnant white dwarf in the distant future. This movement could result from gravitational interactions among the planets or even an external star passing by.

“Our results show that stellar death is not the end—some planets experience a vibrant and lively future after the death of their star,” stated MacDonald. He emphasized the significance of understanding such systems for predicting the future of our own solar system.

Research by MacDonald, O’Connor, and colleagues published in the journal Nature presents new insights with their study titled Aerosols and hydrocarbons in the atmosphere of a white dwarf planet.