The sun, like all stars, will eventually deplete its fuel and die. Scientists predict that in several billion years, our sun will enter the red giant phase, which will result in it expanding and possibly consuming nearby planets such as Mercury and Venus. This phase involves the star expanding and destroying nearby rocky planets.
Astronomers have long debated the fate of Earth and other solar system planets when the sun reaches this phase. A recent discovery by astronomers shows that a giant planet, WD 1856b, managed to survive after its own sun perished. Ryan J. MacDonald from the University of St Andrews explained in an interview with Newsweek that initially, the planets around the dying sun move further away due to the white dwarf having less mass.
However, in the case of WD 1856b, the planet actually moved closer to the white dwarf. This inward migration occurred billions of years after the star’s death, likely due to the gravitational pull from two nearby red dwarf stars.
In 2020, scientists discovered a giant planet orbiting a white dwarf and questioned how it survived the destructive end of its star. A new study using NASA’s James Webb Space Telescope allowed scientists to analyze the planet’s atmosphere, unveiling methane and aerosols present. This study marks a notable achievement as the first characterization of a planet’s atmosphere orbiting a dead star. It highlights that planetary atmospheres can exist even around stellar remnants, offering new opportunities to study planetary systems after their host stars have expired.
Researchers concluded that WD 1856b originally orbited at a safe distance before migrating towards the white dwarf long after the star’s demise. Christopher O’Connor from Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics commented on the implications for our solar system’s future. He noted that when our sun dies in approximately five billion years, the survival of planets into this phase suggests broader possibilities for the locations and timing of habitable planets in the universe.
The gas giant WD 1856b, about 80 light-years from Earth, has a similar radius to Jupiter and orbits a white dwarf, the star’s dense remnant. O’Connor described this planetary system as bizarre, as WD 1856b’s radius is eight times larger than the white dwarf, completing an orbit in just 1.4 days. Its survival through the red giant phase is unexpected, given that sunlike stars expand significantly during this time.
There are two main theories about WD 1856b’s current position. One suggests it survived being engulfed by the star, while another points to gravitational forces from surrounding stars influencing its migration. The NASA telescope’s investigations found that the planet was hotter than anticipated. The researchers proposed that the planet heated up as it moved closer to the white dwarf, possibly 5.5 billion years after it formed.
MacDonald noted that similar migrations might be possible in our solar system, potentially caused by gravitational interactions between giant planets or an encounter with another star in the far future. This planet and star system offers insights into what could happen when our sun eventually dies.
“Our results indicate that stellar death does not signify the end, as some planets may have dynamic futures following their star’s death,” MacDonald stated. This research gives us a glimpse into the potential future of our solar system.
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