Can Atmospheres Survive Stellar Death? Inside White Dwarf Planets

The Surviving Locker

Imagine your school gets completely demolished, but your locker somehow survives untouched in the rubble. That is what it is like when a star dies and its planets stay in one piece. Most stars, including our Sun, will eventually swell into red giants and then shrink into dense, dead stellar embers.

Studying White Dwarf Planets

Astronomers want to understand what happens to these solar systems after their stars collapse. Researchers used the James Webb Space Telescope to examine the atmosphere of WD 1856 b, a giant planet orbiting a dead star. The telescope measured the infrared light passing through the planet's atmosphere to identify its chemical makeup.

The observations measured several specific characteristics:

• A carbon-rich atmosphere containing approximately 7% methane.
• A planetary mass constrained between 4.3 and 10.9 times the mass of Jupiter.
• An actual temperature between 390 and 412 Kelvin, which is much hotter than the expected 160 Kelvin.
• Thermal emission leaking from the planet's nightside.

Friction in the Dark

The temperature difference suggests the planet underwent a massive reheating event billions of years ago. Researchers suggest that gravitational forces squeezed and stretched the planet as its orbit circularised, generating internal heat. This shows that giant planets can migrate closer to dead stars without being torn apart.

This discovery helps us model how planetary atmospheres behave over billions of years. It suggests that giant worlds in our own solar system might endure similar dramatic shifts when our Sun eventually dies.