The James Webb Space Telescope studied the exoplanet WD 1856 b, revealing that its atmosphere contains small cloud particles and hydrocarbons. The findings were published in the journal Nature on July 1, 2026, marking the first time an atmosphere has been detected on a planet transiting a dead star.

WD 1856 b is a gas giant exoplanet that orbits the white dwarf star WD 1856+534 every 34 hours. The planet maintains a separation of less than 2 million miles (3 million kilometers) from its host star, a distance 50 times closer than Earth orbits the Sun. The atmosphere contains small cloud particles and hydrocarbons, most likely methane, according to Victoria Boehm, a co-author at Cornell University.

"We saw the telltale signatures of small cloud particles and hydrocarbons, most likely methane, which is the first time we have seen an atmosphere on a planet transiting a dead star," Boehm said. The planet's temperature measures approximately 260 degrees Fahrenheit (126 degrees Celsius). Its mass falls between four and eleven times the mass of Jupiter. Ryan MacDonald, a lead author from the University of St. Andrews, stated, "The planet is about the size of Jupiter, but the white dwarf it orbits is the size of Earth, so the planet is seven times larger than its star."

Christopher O'Connor, a co-author from Northwestern University, explained that two theories address how WD 1856 b reached its current position. "The big question is how WD 1856 b ended up where it is today, and there are two theories," O'Connor said. "One is that the planet was swallowed by the host star as it was dying, and managed to survive on the inside." The other theory suggests that "migration took place due to the gravitational effect of other objects in the system." He added, "As the planet moved inwards, its interactions with the strong gravity of the white dwarf will have caused it to warm up considerably, and it has been cooling ever since." Researchers concluded that this heating most likely occurred between 3 and 5.5 billion years after the star became a white dwarf.

WD 1856 b was discovered in 2020 by scientists using NASA's TESS and the Spitzer Space Telescope. The white dwarf star WD 1856+534, located about 80 light-years from Earth, is part of a triple star system.