A giant planet that orbits a dead star has surprised scientists once again.
New observations from NASA’s James Webb Space Telescope (JWST) suggest the planet survived its star’s violent death and only moved close to the dead star billions of years later.
The discovery gives scientists a rare look at what could happen to our own solar system in the distant future.
The planet, called WD1856b, was first discovered in 2020.
It is located about 80 light-years from Earth and is between four and 11 times heavier than Jupiter.
What makes it so unusual is that it circles a white dwarf, which is the small, dense remains of a star that has used up all of its fuel.
White dwarfs are only about the size of Earth, even though they contain about as much mass as the Sun. WD1856b is much larger than the white dwarf it orbits.
The planet completes one trip around the dead star in just 1.4 days, making it one of the strangest planetary systems ever found.
Scientists were puzzled because the planet should not have survived its star’s earlier stage as a red giant. When stars like our Sun run out of fuel, they grow to more than 100 times their original size.
During this stage, they often swallow nearby planets before shrinking into white dwarfs. In our own solar system, Mercury and Venus will almost certainly be swallowed when the Sun becomes a red giant. Earth may also face the same fate.
Researchers wanted to know how WD1856b avoided being destroyed. One idea was that the planet was swallowed but somehow survived.
Another idea was that it stayed far away during the dangerous red giant stage and only moved inward much later because of the pull of other stars.
To solve the mystery, scientists used JWST to study the planet’s atmosphere, temperature, and mass. They found the planet is much hotter than expected, with a temperature of about 400 Kelvin, or around 127°C. This is about 240 degrees hotter than the white dwarf alone could explain.
By comparing the planet’s temperature with computer models of how giant planets cool over time, the team was able to work backward through its history.
Their results suggest the planet remained safely far from the star while it expanded into a red giant. Then, around 3 to 5.5 billion years after the star became a white dwarf, the planet slowly moved inward. As it came closer, the white dwarf’s powerful gravity heated the planet. It has been cooling ever since.
The observations also revealed methane gas and clouds in the planet’s atmosphere. This is the first time scientists have successfully studied the atmosphere of a planet orbiting a dead star.
The discovery suggests that the death of a star does not always mean the end of its planetary system. Instead, planets may continue moving and changing for billions of years.
Scientists believe this remarkable system offers a possible glimpse of the far future of our own solar system, showing that even after a star dies, its surviving planets may still have a long and surprising journey ahead.
Source: Northwestern University.
